Fix typo

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

.flake8

@@ -28,7 +28,7 @@ max-line-length = 99
 # - F821: undefined name `name`
 #
 per-file-ignores =
-  var/spack/repos/*/package.py:F403,F405,F821
+  var/spack/*/package.py:F403,F405,F821
   *-ci-package.py:F403,F405,F821
 
 # exclude things we usually do not want linting for.

.gitattributes

@@ -1,4 +1,3 @@
 *.py diff=python
-*.lp linguist-language=Prolog
 lib/spack/external/* linguist-vendored
-*.bat text eol=crlf
+*.bat text eol=crlf

.github/workflows/audit.yaml

@@ -59,7 +59,6 @@ jobs:
     - name: Package audits (without coverage)
       if: ${{ runner.os == 'Windows' }}
       run: |
-          . share/spack/setup-env.sh
           spack -d audit packages
           ./share/spack/qa/validate_last_exit.ps1
           spack -d audit configs

.github/workflows/bootstrap.yml

@@ -26,7 +26,7 @@ jobs:
           dnf install -y \
               bzip2 curl file gcc-c++ gcc gcc-gfortran git gzip \
               make patch unzip which xz python3 python3-devel tree \
-              cmake bison bison-devel libstdc++-static
+              cmake bison bison-devel libstdc++-static gawk
       - name: Setup OpenSUSE
         if: ${{ matrix.image == 'opensuse/leap:latest' }}
         run: |

.github/workflows/ci.yaml

@@ -42,17 +42,17 @@ jobs:
           # built-in repository or documentation
           filters: |
             bootstrap:
-            - 'var/spack/repos/builtin/packages/clingo-bootstrap/**'
-            - 'var/spack/repos/builtin/packages/clingo/**'
-            - 'var/spack/repos/builtin/packages/python/**'
-            - 'var/spack/repos/builtin/packages/re2c/**'
-            - 'var/spack/repos/builtin/packages/gnupg/**'
-            - 'var/spack/repos/builtin/packages/libassuan/**'
-            - 'var/spack/repos/builtin/packages/libgcrypt/**'
-            - 'var/spack/repos/builtin/packages/libgpg-error/**'
-            - 'var/spack/repos/builtin/packages/libksba/**'
-            - 'var/spack/repos/builtin/packages/npth/**'
-            - 'var/spack/repos/builtin/packages/pinentry/**'
+            - 'var/spack/repos/spack_repo/builtin/packages/clingo-bootstrap/**'
+            - 'var/spack/repos/spack_repo/builtin/packages/clingo/**'
+            - 'var/spack/repos/spack_repo/builtin/packages/python/**'
+            - 'var/spack/repos/spack_repo/builtin/packages/re2c/**'
+            - 'var/spack/repos/spack_repo/builtin/packages/gnupg/**'
+            - 'var/spack/repos/spack_repo/builtin/packages/libassuan/**'
+            - 'var/spack/repos/spack_repo/builtin/packages/libgcrypt/**'
+            - 'var/spack/repos/spack_repo/builtin/packages/libgpg-error/**'
+            - 'var/spack/repos/spack_repo/builtin/packages/libksba/**'
+            - 'var/spack/repos/spack_repo/builtin/packages/npth/**'
+            - 'var/spack/repos/spack_repo/builtin/packages/pinentry/**'
             - 'lib/spack/**'
             - 'share/spack/**'
             - '.github/workflows/bootstrap.yml'

.github/workflows/prechecks.yml

@@ -25,14 +25,16 @@ jobs:
       with:
         python-version: '3.13'
         cache: 'pip'
+        cache-dependency-path: '.github/workflows/requirements/style/requirements.txt'
     - name: Install Python Packages
       run: |
-        pip install --upgrade pip setuptools
         pip install -r .github/workflows/requirements/style/requirements.txt
     - name: vermin (Spack's Core)
-      run: vermin --backport importlib --backport argparse --violations --backport typing -t=3.6- -vvv lib/spack/spack/ lib/spack/llnl/ bin/
+      run: |
+        vermin --backport importlib --backport argparse --violations --backport typing -t=3.6- -vvv lib/spack/spack/ lib/spack/llnl/ bin/
     - name: vermin (Repositories)
-      run: vermin --backport importlib --backport argparse --violations --backport typing -t=3.6- -vvv var/spack/repos
+      run: |
+        vermin --backport importlib --backport argparse --violations --backport typing -t=3.6- -vvv var/spack/repos var/spack/test_repos
 
   # Run style checks on the files that have been changed
   style:
@@ -40,23 +42,20 @@ jobs:
     steps:
     - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683
       with:
-        fetch-depth: 0
+        fetch-depth: 2
     - uses: actions/setup-python@0b93645e9fea7318ecaed2b359559ac225c90a2b
       with:
         python-version: '3.13'
         cache: 'pip'
+        cache-dependency-path: '.github/workflows/requirements/style/requirements.txt'
     - name: Install Python packages
       run: |
-        pip install --upgrade pip setuptools
         pip install -r .github/workflows/requirements/style/requirements.txt
-    - name: Setup git configuration
-      run: |
-        # Need this for the git tests to succeed.
-        git --version
-        . .github/workflows/bin/setup_git.sh
     - name: Run style tests
       run: |
-          share/spack/qa/run-style-tests
+        bin/spack style --base HEAD^1
+        bin/spack license verify
+        pylint -j $(nproc) --disable=all --enable=unspecified-encoding --ignore-paths=lib/spack/external lib
 
   audit:
     uses: ./.github/workflows/audit.yaml
@@ -66,7 +65,11 @@ jobs:
       python_version: '3.13'
 
   verify-checksums:
-    if: ${{ inputs.with_packages == 'true' }}
+    # do not run if the commit message or PR description contains [skip-verify-checksums]
+    if: >-
+      ${{ inputs.with_packages == 'true' &&
+      !contains(github.event.pull_request.body, '[skip-verify-checksums]') &&
+      !contains(github.event.head_commit.message, '[skip-verify-checksums]') }}
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@a5ac7e51b41094c92402da3b24376905380afc29
@@ -103,21 +106,3 @@ jobs:
           spack -d bootstrap now --dev
           spack -d style -t black
           spack unit-test -V
-
-  # Further style checks from pylint
-  pylint:
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683
-        with:
-          fetch-depth: 0
-      - uses: actions/setup-python@0b93645e9fea7318ecaed2b359559ac225c90a2b
-        with:
-          python-version: '3.13'
-          cache: 'pip'
-      - name: Install Python packages
-        run: |
-          pip install --upgrade pip setuptools pylint
-      - name: Pylint (Spack Core)
-        run: |
-          pylint -j 4 --disable=all --enable=unspecified-encoding --ignore-paths=lib/spack/external lib

.github/workflows/requirements/style/requirements.txt

@@ -1,7 +1,8 @@
 black==25.1.0
-clingo==5.7.1
-flake8==7.1.2
+clingo==5.8.0
+flake8==7.2.0
 isort==6.0.1
 mypy==1.15.0
-types-six==1.17.0.20250304
+types-six==1.17.0.20250403
 vermin==1.6.0
+pylint==3.3.7

.github/workflows/unit_tests.yaml

@@ -19,9 +19,6 @@ jobs:
         on_develop:
         - ${{ github.ref == 'refs/heads/develop' }}
         include:
-        - python-version: '3.6'
-          os: ubuntu-20.04
-          on_develop: ${{ github.ref == 'refs/heads/develop' }}
         - python-version: '3.7'
           os: ubuntu-22.04
           on_develop: ${{ github.ref == 'refs/heads/develop' }}

README.md

@@ -46,18 +46,42 @@ See the
 [Feature Overview](https://spack.readthedocs.io/en/latest/features.html)
 for examples and highlights.
 
-To install spack and your first package, make sure you have Python & Git.
+Installation
+----------------
+
+To install spack, first make sure you have Python & Git.
 Then:
 
-    $ git clone -c feature.manyFiles=true --depth=2 https://github.com/spack/spack.git
-    $ cd spack/bin
-    $ ./spack install zlib
+```bash
+git clone -c feature.manyFiles=true --depth=2 https://github.com/spack/spack.git
+```
+
+<details>
+<summary>What are <code>manyFiles=true</code> and <code>--depth=2</code>?</summary>
+<br>
 
-> [!TIP]
 > `-c feature.manyFiles=true` improves git's performance on repositories with 1,000+ files.
 >
 > `--depth=2` prunes the git history to reduce the size of the Spack installation.
 
+</details>
+
+```bash
+# For bash/zsh/sh
+. spack/share/spack/setup-env.sh
+
+# For tcsh/csh
+source spack/share/spack/setup-env.csh
+
+# For fish
+. spack/share/spack/setup-env.fish
+```
+
+```bash
+# Now you're ready to install a package!
+spack install zlib-ng
+```
+
 Documentation
 ----------------
 

etc/spack/defaults/config.yaml

@@ -90,10 +90,9 @@ config:
   misc_cache: $user_cache_path/cache
 
 
-  # Timeout in seconds used for downloading sources etc. This only applies
-  # to the connection phase and can be increased for slow connections or
-  # servers. 0 means no timeout.
-  connect_timeout: 10
+  # Abort downloads after this many seconds if not data is received.
+  # Setting this to 0 will disable the timeout.
+  connect_timeout: 30
 
 
   # If this is false, tools like curl that use SSL will not verify

etc/spack/defaults/darwin/packages.yaml

@@ -25,6 +25,8 @@ packages:
       glu: [apple-glu]
       unwind: [apple-libunwind]
       uuid: [apple-libuuid]
+  apple-clang:
+    buildable: false
   apple-gl:
     buildable: false
     externals:

etc/spack/defaults/packages.yaml

@@ -72,6 +72,8 @@ packages:
     permissions:
       read: world
       write: user
+  cce:
+    buildable: false
   cray-fftw:
     buildable: false
   cray-libsci:
@@ -86,13 +88,23 @@ packages:
     buildable: false
   essl:
     buildable: false
+  fj:
+    buildable: false
   fujitsu-mpi:
     buildable: false
   fujitsu-ssl2:
     buildable: false
+  glibc:
+    buildable: false
   hpcx-mpi:
     buildable: false
+  iconv:
+    prefer: [libiconv]
   mpt:
     buildable: false
+  musl:
+    buildable: false
   spectrum-mpi:
     buildable: false
+  xl:
+    buildable: false

etc/spack/defaults/repos.yaml

@@ -11,4 +11,4 @@
 #   ~/.spack/repos.yaml
 # -------------------------------------------------------------------------
 repos:
-  - $spack/var/spack/repos/builtin
+  - $spack/var/spack/repos/spack_repo/builtin

etc/spack/defaults/windows/packages.yaml

@@ -20,3 +20,8 @@ packages:
       cxx: [msvc]
       mpi: [msmpi]
       gl: [wgl]
+  mpi:
+    require:
+    - one_of: [msmpi]
+  msvc:
+    buildable: false

lib/spack/docs/basic_usage.rst

@@ -1291,55 +1291,61 @@ based on site policies.
 Variants
 ^^^^^^^^
 
-Variants are named options associated with a particular package. They are
-optional, as each package must provide default values for each variant it
-makes available. Variants can be specified using
-a flexible parameter syntax ``name=<value>``. For example,
-``spack install mercury debug=True`` will install mercury built with debug
-flags. The names of particular variants available for a package depend on
+Variants are named options associated with a particular package and are
+typically used to enable or disable certain features at build time. They
+are optional, as each package must provide default values for each variant
+it makes available.
+
+The names of variants available for a particular package depend on
 what was provided by the package author. ``spack info <package>`` will
 provide information on what build variants are available.
 
-For compatibility with earlier versions, variants which happen to be
-boolean in nature can be specified by a syntax that represents turning
-options on and off. For example, in the previous spec we could have
-supplied ``mercury +debug`` with the same effect of enabling the debug
-compile time option for the libelf package.
+There are different types of variants:
 
-Depending on the package a variant may have any default value.  For
-``mercury`` here, ``debug`` is ``False`` by default, and we turned it on
-with ``debug=True`` or ``+debug``.  If a variant is ``True`` by default
-you can turn it off by either adding ``-name`` or ``~name`` to the spec.
+1. Boolean variants. Typically used to enable or disable a feature at
+   compile time. For example, a package might have a ``debug`` variant that
+   can be explicitly enabled with ``+debug`` and disabled with ``~debug``.
+2. Single-valued variants. Often used to set defaults. For example, a package
+   might have a ``compression`` variant that determines the default
+   compression algorithm, which users could set to ``compression=gzip`` or
+   ``compression=zstd``.
+3. Multi-valued variants. A package might have a ``fabrics`` variant that
+   determines which network fabrics to support. Users could set this to
+   ``fabrics=verbs,ofi`` to enable both InfiniBand verbs and OpenFabrics
+   interfaces. The values are separated by commas.
 
-There are two syntaxes here because, depending on context, ``~`` and
-``-`` may mean different things.  In most shells, the following will
-result in the shell performing home directory substitution:
+   The meaning of ``fabrics=verbs,ofi`` is to enable *at least* the specified
+   fabrics, but other fabrics may be enabled as well. If the intent is to
+   enable *only* the specified fabrics, then the ``fabrics:=verbs,ofi``
+   syntax should be used with the ``:=`` operator.
 
-.. code-block:: sh
+.. note::
 
-   mpileaks ~debug   # shell may try to substitute this!
-   mpileaks~debug    # use this instead
+   In certain shells, the the ``~`` character is expanded to the home
+   directory. To avoid these issues, avoid whitespace between the package
+   name and the variant:
 
-If there is a user called ``debug``, the ``~`` will be incorrectly
-expanded.  In this situation, you would want to write ``libelf
--debug``.  However, ``-`` can be ambiguous when included after a
-package name without spaces:
+   .. code-block:: sh
 
-.. code-block:: sh
+      mpileaks ~debug   # shell may try to substitute this!
+      mpileaks~debug    # use this instead
 
-   mpileaks-debug     # wrong!
-   mpileaks -debug    # right
+   Alternatively, you can use the ``-`` character to disable a variant,
+   but be aware that this requires a space between the package name and
+   the variant:
 
-Spack allows the ``-`` character to be part of package names, so the
-above will be interpreted as a request for the ``mpileaks-debug``
-package, not a request for ``mpileaks`` built without ``debug``
-options.  In this scenario, you should write ``mpileaks~debug`` to
-avoid ambiguity.
+   .. code-block:: sh
 
-When spack normalizes specs, it prints them out with no spaces boolean
-variants using the backwards compatibility syntax and uses only ``~``
-for disabled boolean variants.  The ``-`` and spaces on the command
-line are provided for convenience and legibility.
+      mpileaks-debug     # wrong: refers to a package named "mpileaks-debug"
+      mpileaks -debug    # right: refers to a package named mpileaks with debug disabled
+
+   As a last resort, ``debug=False`` can also be used to disable a boolean variant.
+
+
+
+"""""""""""""""""""""""""""""""""""
+Variant propagation to dependencies
+"""""""""""""""""""""""""""""""""""
 
 Spack allows variants to propagate their value to the package's
 dependency by using ``++``, ``--``, and ``~~`` for boolean variants.
@@ -1409,27 +1415,29 @@ that executables will run without the need to set ``LD_LIBRARY_PATH``.
 
 .. code-block:: yaml
 
-  compilers:
-    - compiler:
-        spec: gcc@4.9.3
-        paths:
-          cc: /opt/gcc/bin/gcc
-          c++: /opt/gcc/bin/g++
-          f77: /opt/gcc/bin/gfortran
-          fc: /opt/gcc/bin/gfortran
-        environment:
-          unset:
-            - BAD_VARIABLE
-          set:
-            GOOD_VARIABLE_NUM: 1
-            GOOD_VARIABLE_STR: good
-          prepend_path:
-            PATH: /path/to/binutils
-          append_path:
-            LD_LIBRARY_PATH: /opt/gcc/lib
-        extra_rpaths:
-        - /path/to/some/compiler/runtime/directory
-        - /path/to/some/other/compiler/runtime/directory
+  packages:
+    gcc:
+      externals:
+      - spec: gcc@4.9.3
+        prefix: /opt/gcc
+        extra_attributes:
+          compilers:
+            c: /opt/gcc/bin/gcc
+            cxx: /opt/gcc/bin/g++
+            fortran: /opt/gcc/bin/gfortran
+          environment:
+            unset:
+              - BAD_VARIABLE
+            set:
+              GOOD_VARIABLE_NUM: 1
+              GOOD_VARIABLE_STR: good
+            prepend_path:
+              PATH: /path/to/binutils
+            append_path:
+              LD_LIBRARY_PATH: /opt/gcc/lib
+          extra_rpaths:
+          - /path/to/some/compiler/runtime/directory
+          - /path/to/some/other/compiler/runtime/directory
 
 
 ^^^^^^^^^^^^^^^^^^^^^^^
@@ -1908,7 +1916,7 @@ diagnostics. Issues, if found, are reported to stdout:
    PKG-DIRECTIVES: 1 issue found
    1. lammps: wrong variant in "conflicts" directive
        the variant 'adios' does not exist
-       in /home/spack/spack/var/spack/repos/builtin/packages/lammps/package.py
+       in /home/spack/spack/var/spack/repos/spack_repo/builtin/packages/lammps/package.py
 
 
 ------------

lib/spack/docs/build_systems.rst

@@ -63,7 +63,6 @@ on these ideas for each distinct build system that Spack supports:
    build_systems/cudapackage
    build_systems/custompackage
    build_systems/inteloneapipackage
-   build_systems/intelpackage
    build_systems/rocmpackage
    build_systems/sourceforgepackage
 
@@ -84,7 +83,7 @@ packages. You can quickly find examples by running:
 
 .. code-block:: console
 
-   $ cd var/spack/repos/builtin/packages
+   $ cd var/spack/repos/spack_repo/builtin/packages
    $ grep -l QMakePackage */package.py
 
 

lib/spack/docs/build_systems/bundlepackage.rst

@@ -27,10 +27,10 @@ it could use the ``require`` directive as follows:
 
 Spack has a number of built-in bundle packages, such as:
 
-* `AmdAocl <https://github.com/spack/spack/blob/develop/var/spack/repos/builtin/packages/amd-aocl/package.py>`_
-* `EcpProxyApps <https://github.com/spack/spack/blob/develop/var/spack/repos/builtin/packages/ecp-proxy-apps/package.py>`_
-* `Libc <https://github.com/spack/spack/blob/develop/var/spack/repos/builtin/packages/libc/package.py>`_
-* `Xsdk <https://github.com/spack/spack/blob/develop/var/spack/repos/builtin/packages/xsdk/package.py>`_
+* `AmdAocl <https://github.com/spack/spack/blob/develop/var/spack/repos/spack_repo/builtin/packages/amd_aocl/package.py>`_
+* `EcpProxyApps <https://github.com/spack/spack/blob/develop/var/spack/repos/spack_repo/builtin/packages/ecp_proxy_apps/package.py>`_
+* `Libc <https://github.com/spack/spack/blob/develop/var/spack/repos/spack_repo/builtin/packages/libc/package.py>`_
+* `Xsdk <https://github.com/spack/spack/blob/develop/var/spack/repos/spack_repo/builtin/packages/xsdk/package.py>`_
 
 where ``Xsdk`` also inherits from ``CudaPackage`` and ``RocmPackage`` and
 ``Libc`` is a virtual bundle package for the C standard library.

lib/spack/docs/build_systems/cmakepackage.rst

@@ -199,7 +199,7 @@ a variant to control this:
 However, not every CMake package accepts all four of these options.
 Grep the ``CMakeLists.txt`` file to see if the default values are
 missing or replaced. For example, the
-`dealii <https://github.com/spack/spack/blob/develop/var/spack/repos/builtin/packages/dealii/package.py>`_
+`dealii <https://github.com/spack/spack/blob/develop/var/spack/repos/spack_repo/builtin/packages/dealii/package.py>`_
 package overrides the default variant with:
 
 .. code-block:: python

lib/spack/docs/build_systems/custompackage.rst

@@ -20,8 +20,8 @@ start is to look at the definitions of other build systems. This guide
 focuses mostly on how Spack's build systems work.
 
 In this guide, we will be using the
-`perl <https://github.com/spack/spack/blob/develop/var/spack/repos/builtin/packages/perl/package.py>`_ and
-`cmake <https://github.com/spack/spack/blob/develop/var/spack/repos/builtin/packages/cmake/package.py>`_
+`perl <https://github.com/spack/spack/blob/develop/var/spack/repos/spack_repo/builtin/packages/perl/package.py>`_ and
+`cmake <https://github.com/spack/spack/blob/develop/var/spack/repos/spack_repo/builtin/packages/cmake/package.py>`_
 packages as examples. ``perl``'s build system is a hand-written
 ``Configure`` shell script, while ``cmake`` bootstraps itself during
 installation. Both of these packages require custom build systems.

lib/spack/docs/build_systems/inteloneapipackage.rst

@@ -33,9 +33,6 @@ For more information on a specific package, do::
 
   spack info --all <package-name>
 
-Intel no longer releases new versions of Parallel Studio, which can be
-used in Spack via the :ref:`intelpackage`. All of its components can
-now be found in oneAPI.
 
 Examples
 ========
@@ -50,34 +47,8 @@ Install the oneAPI compilers::
 
   spack install intel-oneapi-compilers
 
-Add the compilers to your ``compilers.yaml`` so spack can use them::
 
-  spack compiler add `spack location -i intel-oneapi-compilers`/compiler/latest/bin
-
-Verify that the compilers are available::
-
-  spack compiler list
-
-Note that 2024 and later releases do not include ``icc``. Before 2024,
-the package layout was different::
-  
-  spack compiler add `spack location -i intel-oneapi-compilers`/compiler/latest/linux/bin/intel64
-  spack compiler add `spack location -i intel-oneapi-compilers`/compiler/latest/linux/bin
-
-The ``intel-oneapi-compilers`` package includes 2 families of
-compilers:
-
-* ``intel``: ``icc``, ``icpc``, ``ifort``. Intel's *classic*
-  compilers. 2024 and later releases contain ``ifort``, but not
-  ``icc`` and ``icpc``.
-* ``oneapi``: ``icx``, ``icpx``, ``ifx``. Intel's new generation of
-  compilers based on LLVM.
-
-To build the ``patchelf`` Spack package with ``icc``, do::
-
-  spack install patchelf%intel
-
-To build with with ``icx``, do ::
+To build the ``patchelf`` Spack package with ``icx``, do::
 
   spack install patchelf%oneapi
 
@@ -92,15 +63,6 @@ Install the oneAPI compilers::
 
   spack install intel-oneapi-compilers
 
-Add the compilers to your ``compilers.yaml`` so Spack can use them::
-
-  spack compiler add `spack location -i intel-oneapi-compilers`/compiler/latest/bin
-  spack compiler add `spack location -i intel-oneapi-compilers`/compiler/latest/bin
-
-Verify that the compilers are available::
-
-  spack compiler list
-
 Clone `spack-configs <https://github.com/spack/spack-configs>`_ repo and activate Intel oneAPI CPU environment::
 
   git clone https://github.com/spack/spack-configs
@@ -149,7 +111,7 @@ Compilers
 ---------
 
 To use the compilers, add some information about the installation to
-``compilers.yaml``. For most users, it is sufficient to do::
+``packages.yaml``. For most users, it is sufficient to do::
 
   spack compiler add /opt/intel/oneapi/compiler/latest/bin
 
@@ -157,7 +119,7 @@ Adapt the paths above if you did not install the tools in the default
 location. After adding the compilers, using them is the same
 as if you had installed the ``intel-oneapi-compilers`` package.
 Another option is to manually add the configuration to
-``compilers.yaml`` as described in :ref:`Compiler configuration
+``packages.yaml`` as described in :ref:`Compiler configuration
 <compiler-config>`.
 
 Before 2024, the directory structure was different::
@@ -200,15 +162,5 @@ You can also use Spack-installed libraries. For example::
 Will update your environment CPATH, LIBRARY_PATH, and other
 environment variables for building an application with oneMKL.
 
-More information
-================
-
-This section describes basic use of oneAPI, especially if it has
-changed compared to Parallel Studio. See :ref:`intelpackage` for more
-information on :ref:`intel-virtual-packages`,
-:ref:`intel-unrelated-packages`,
-:ref:`intel-integrating-external-libraries`, and
-:ref:`using-mkl-tips`.
-
 
 .. _`Intel installers`: https://software.intel.com/content/www/us/en/develop/documentation/installation-guide-for-intel-oneapi-toolkits-linux/top.html

lib/spack/docs/build_systems/makefilepackage.rst

@@ -91,14 +91,14 @@ there are any other variables you need to set, you can do this in the
 
 .. code-block:: python
 
-   def setup_build_environment(self, env):
+   def setup_build_environment(self, env: EnvironmentModifications) -> None:
        env.set("PREFIX", prefix)
        env.set("BLASLIB", spec["blas"].libs.ld_flags)
 
 
-`cbench <https://github.com/spack/spack/blob/develop/var/spack/repos/builtin/packages/cbench/package.py>`_
+`cbench <https://github.com/spack/spack/blob/develop/var/spack/repos/spack_repo/builtin/packages/cbench/package.py>`_
 is a good example of a simple package that does this, while
-`esmf <https://github.com/spack/spack/blob/develop/var/spack/repos/builtin/packages/esmf/package.py>`_
+`esmf <https://github.com/spack/spack/blob/develop/var/spack/repos/spack_repo/builtin/packages/esmf/package.py>`_
 is a good example of a more complex package.
 
 """"""""""""""""""""""
@@ -129,7 +129,7 @@ If you do need access to the spec, you can create a property like so:
        ]
 
 
-`cloverleaf <https://github.com/spack/spack/blob/develop/var/spack/repos/builtin/packages/cloverleaf/package.py>`_
+`cloverleaf <https://github.com/spack/spack/blob/develop/var/spack/repos/spack_repo/builtin/packages/cloverleaf/package.py>`_
 is a good example of a package that uses this strategy.
 
 """""""""""""
@@ -152,7 +152,7 @@ and a ``filter`` method to help with this. For example:
        makefile.filter(r"^\s*FC\s*=.*",  f"FC = {spack_fc}")
 
 
-`stream <https://github.com/spack/spack/blob/develop/var/spack/repos/builtin/packages/stream/package.py>`_
+`stream <https://github.com/spack/spack/blob/develop/var/spack/repos/spack_repo/builtin/packages/stream/package.py>`_
 is a good example of a package that involves editing a Makefile to set
 the appropriate variables.
 
@@ -192,7 +192,7 @@ well for storing variables:
                inc.write(f"{key} = {config[key]}\n")
 
 
-`elk <https://github.com/spack/spack/blob/develop/var/spack/repos/builtin/packages/elk/package.py>`_
+`elk <https://github.com/spack/spack/blob/develop/var/spack/repos/spack_repo/builtin/packages/elk/package.py>`_
 is a good example of a package that uses a dictionary to store
 configuration variables.
 
@@ -213,7 +213,7 @@ them in a list:
                inc.write(f"{var}\n")
 
 
-`hpl <https://github.com/spack/spack/blob/develop/var/spack/repos/builtin/packages/hpl/package.py>`_
+`hpl <https://github.com/spack/spack/blob/develop/var/spack/repos/spack_repo/builtin/packages/hpl/package.py>`_
 is a good example of a package that uses a list to store
 configuration variables.
 

lib/spack/docs/build_systems/rocmpackage.rst

@@ -12,8 +12,7 @@ The ``ROCmPackage`` is not a build system but a helper package. Like ``CudaPacka
 it provides standard variants, dependencies, and conflicts to facilitate building
 packages using GPUs though for AMD in this case.
 
-You can find the source for this package (and suggestions for setting up your
-``compilers.yaml`` and ``packages.yaml`` files) at
+You can find the source for this package (and suggestions for setting up your ``packages.yaml`` file) at
 `<https://github.com/spack/spack/blob/develop/lib/spack/spack/build_systems/rocm.py>`__.
 
 ^^^^^^^^

lib/spack/docs/build_systems/rpackage.rst

@@ -39,7 +39,7 @@ for "CRAN <package-name>" and you should quickly find what you want.
 If it isn't on CRAN, try Bioconductor, another common R repository.
 
 For the purposes of this tutorial, we will be walking through
-`r-caret <https://github.com/spack/spack/blob/develop/var/spack/repos/builtin/packages/r-caret/package.py>`_
+`r-caret <https://github.com/spack/spack/blob/develop/var/spack/repos/spack_repo/builtin/packages/r_caret/package.py>`_
 as an example. If you search for "CRAN caret", you will quickly find what
 you are looking for at https://cran.r-project.org/package=caret.
 https://cran.r-project.org is the main CRAN website. However, CRAN also
@@ -337,7 +337,7 @@ Non-R dependencies
 ^^^^^^^^^^^^^^^^^^
 
 Some packages depend on non-R libraries for linking. Check out the
-`r-stringi <https://github.com/spack/spack/blob/develop/var/spack/repos/builtin/packages/r-stringi/package.py>`_
+`r-stringi <https://github.com/spack/spack/blob/develop/var/spack/repos/spack_repo/builtin/packages/r_stringi/package.py>`_
 package for an example: https://cloud.r-project.org/package=stringi.
 If you search for the text "SystemRequirements", you will see:
 
@@ -352,7 +352,7 @@ Passing arguments to the installation
 
 Some R packages provide additional flags that can be passed to
 ``R CMD INSTALL``, often to locate non-R dependencies.
-`r-rmpi <https://github.com/spack/spack/blob/develop/var/spack/repos/builtin/packages/r-rmpi/package.py>`_
+`r-rmpi <https://github.com/spack/spack/blob/develop/var/spack/repos/spack_repo/builtin/packages/r_rmpi/package.py>`_
 is an example of this, and flags for linking to an MPI library. To pass
 these to the installation command, you can override ``configure_args``
 like so:

lib/spack/docs/build_systems/sconspackage.rst

@@ -104,10 +104,10 @@ Finding available options
 
 The first place to start when looking for a list of valid options to
 build a package is ``scons --help``. Some packages like
-`kahip <https://github.com/spack/spack/blob/develop/var/spack/repos/builtin/packages/kahip/package.py>`_
+`kahip <https://github.com/spack/spack/blob/develop/var/spack/repos/spack_repo/builtin/packages/kahip/package.py>`_
 don't bother overwriting the default SCons help message, so this isn't
 very useful, but other packages like
-`serf <https://github.com/spack/spack/blob/develop/var/spack/repos/builtin/packages/serf/package.py>`_
+`serf <https://github.com/spack/spack/blob/develop/var/spack/repos/spack_repo/builtin/packages/serf/package.py>`_
 print a list of valid command-line variables:
 
 .. code-block:: console
@@ -177,7 +177,7 @@ print a list of valid command-line variables:
 
 
 More advanced packages like
-`cantera <https://github.com/spack/spack/blob/develop/var/spack/repos/builtin/packages/cantera/package.py>`_
+`cantera <https://github.com/spack/spack/blob/develop/var/spack/repos/spack_repo/builtin/packages/cantera/package.py>`_
 use ``scons --help`` to print a list of subcommands:
 
 .. code-block:: console

lib/spack/docs/conf.py

@@ -225,8 +225,14 @@ def setup(sphinx):
     ("py:class", "llnl.util.lang.T"),
     ("py:class", "llnl.util.lang.KT"),
     ("py:class", "llnl.util.lang.VT"),
+    ("py:class", "llnl.util.lang.K"),
+    ("py:class", "llnl.util.lang.V"),
+    ("py:class", "llnl.util.lang.ClassPropertyType"),
     ("py:obj", "llnl.util.lang.KT"),
     ("py:obj", "llnl.util.lang.VT"),
+    ("py:obj", "llnl.util.lang.ClassPropertyType"),
+    ("py:obj", "llnl.util.lang.K"),
+    ("py:obj", "llnl.util.lang.V"),
 ]
 
 # The reST default role (used for this markup: `text`) to use for all documents.

lib/spack/docs/config_yaml.rst

@@ -148,15 +148,16 @@ this can expose you to attacks.  Use at your own risk.
 ``ssl_certs``
 --------------------
 
-Path to custom certificats for SSL verification. The value can be a 
+Path to custom certificats for SSL verification. The value can be a
 filesytem path, or an environment variable that expands to an absolute file path.
 The default value is set to the environment variable ``SSL_CERT_FILE``
 to use the same syntax used by many other applications that automatically
 detect custom certificates.
 When ``url_fetch_method:curl`` the ``config:ssl_certs`` should resolve to
 a single file.  Spack will then set the environment variable ``CURL_CA_BUNDLE``
-in the subprocess calling ``curl``.
-If ``url_fetch_method:urllib`` then files and directories are supported i.e. 
+in the subprocess calling ``curl``. If additional ``curl`` arguments are required,
+they can be set in the config, e.g. ``url_fetch_method:'curl -k -q'``.
+If ``url_fetch_method:urllib`` then files and directories are supported i.e.
 ``config:ssl_certs:$SSL_CERT_FILE`` or ``config:ssl_certs:$SSL_CERT_DIR``
 will work.
 In all cases the expanded path must be absolute for Spack to use the certificates.

lib/spack/docs/configuration.rst

@@ -11,7 +11,7 @@ Configuration Files
 Spack has many configuration files.  Here is a quick list of them, in
 case you want to skip directly to specific docs:
 
-* :ref:`compilers.yaml <compiler-config>`
+* :ref:`packages.yaml <compiler-config>`
 * :ref:`concretizer.yaml <concretizer-options>`
 * :ref:`config.yaml <config-yaml>`
 * :ref:`include.yaml <include-yaml>`
@@ -46,6 +46,12 @@ Each Spack configuration file is nested under a top-level section
 corresponding to its name. So, ``config.yaml`` starts with ``config:``,
 ``mirrors.yaml`` starts with ``mirrors:``, etc.
 
+.. tip::
+
+   Validation and autocompletion of Spack config files can be enabled in
+   your editor with the YAML language server. See `spack/schemas
+   <https://github.com/spack/schemas>`_ for more information.
+
 .. _configuration-scopes:
 
 --------------------
@@ -95,7 +101,7 @@ are six configuration scopes. From lowest to highest:
    precedence over all other scopes.
 
 Each configuration directory may contain several configuration files,
-such as ``config.yaml``, ``compilers.yaml``, or ``mirrors.yaml``.  When
+such as ``config.yaml``, ``packages.yaml``, or ``mirrors.yaml``.  When
 configurations conflict, settings from higher-precedence scopes override
 lower-precedence settings.
 

lib/spack/docs/contribution_guide.rst

@@ -226,9 +226,9 @@ If all is well, you'll see something like this:
 
    Modified files:
 
-     var/spack/repos/builtin/packages/hdf5/package.py
-     var/spack/repos/builtin/packages/hdf/package.py
-     var/spack/repos/builtin/packages/netcdf/package.py
+     var/spack/repos/spack_repo/builtin/packages/hdf5/package.py
+     var/spack/repos/spack_repo/builtin/packages/hdf/package.py
+     var/spack/repos/spack_repo/builtin/packages/netcdf/package.py
    =======================================================
    Flake8 checks were clean.
 
@@ -236,9 +236,9 @@ However, if you aren't compliant with PEP 8, flake8 will complain:
 
 .. code-block:: console
 
-   var/spack/repos/builtin/packages/netcdf/package.py:26: [F401] 'os' imported but unused
-   var/spack/repos/builtin/packages/netcdf/package.py:61: [E303] too many blank lines (2)
-   var/spack/repos/builtin/packages/netcdf/package.py:106: [E501] line too long (92 > 79 characters)
+   var/spack/repos/spack_repo/builtin/packages/netcdf/package.py:26: [F401] 'os' imported but unused
+   var/spack/repos/spack_repo/builtin/packages/netcdf/package.py:61: [E303] too many blank lines (2)
+   var/spack/repos/spack_repo/builtin/packages/netcdf/package.py:106: [E501] line too long (92 > 79 characters)
    Flake8 found errors.
 
 Most of the error messages are straightforward, but if you don't understand what
@@ -280,7 +280,7 @@ All of these can be installed with Spack, e.g.
 
 .. warning::
 
-   Sphinx has `several required dependencies <https://github.com/spack/spack/blob/develop/var/spack/repos/builtin/packages/py-sphinx/package.py>`_.
+   Sphinx has `several required dependencies <https://github.com/spack/spack/blob/develop/var/spack/repos/spack_repo/builtin/packages/py-sphinx/package.py>`_.
    If you're using a ``python`` from Spack and you installed
    ``py-sphinx`` and friends, you need to make them available to your
    ``python``. The easiest way to do this is to run:

lib/spack/docs/developer_guide.rst

@@ -154,9 +154,7 @@ Package-related modules
 
 :mod:`spack.util.naming`
   Contains functions for mapping between Spack package names,
-  Python module names, and Python class names. Functions like
-  :func:`~spack.util.naming.mod_to_class` handle mapping package
-  module names to class names.
+  Python module names, and Python class names.
 
 :mod:`spack.directives`
   *Directives* are functions that can be called inside a package definition

lib/spack/docs/env_vars_yaml.rst

@@ -0,0 +1,34 @@
+.. Copyright Spack Project Developers. See COPYRIGHT file for details.
+
+   SPDX-License-Identifier: (Apache-2.0 OR MIT)
+
+.. _env-vars-yaml:
+
+=============================================
+Environment Variable Settings (env_vars.yaml)
+=============================================
+
+Spack allows you to include shell environment variable modifications
+for a spack environment by including an ``env_vars.yaml``.  Environment
+varaibles can be modified by setting, unsetting, appending, and prepending
+variables in the shell environment.
+The changes to the shell environment will take effect when the spack
+environment is activated.
+
+for example,
+
+.. code-block:: yaml
+
+  env_vars:
+    set:
+      ENVAR_TO_SET_IN_ENV_LOAD: "FOO"
+    unset:
+      ENVAR_TO_UNSET_IN_ENV_LOAD:
+    prepend_path:
+      PATH_LIST: "path/to/prepend"
+    append_path:
+      PATH_LIST: "path/to/append"
+    remove_path:
+      PATH_LIST: "path/to/remove"
+
+

lib/spack/docs/environments.rst

@@ -667,11 +667,11 @@ a ``packages.yaml`` file) could contain:
      # ...
      packages:
        all:
-         compiler: [intel]
+         providers:
+           mpi: [openmpi]
      # ...
 
-This configuration sets the default compiler for all packages to
-``intel``.
+This configuration sets the default mpi provider to be openmpi.
 
 ^^^^^^^^^^^^^^^^^^^^^^^
 Included configurations
@@ -686,7 +686,8 @@ the environment.
    spack:
      include:
      - environment/relative/path/to/config.yaml
-     - https://github.com/path/to/raw/config/compilers.yaml
+     - path: https://github.com/path/to/raw/config/compilers.yaml
+       sha256: 26e871804a92cd07bb3d611b31b4156ae93d35b6a6d6e0ef3a67871fcb1d258b
      - /absolute/path/to/packages.yaml
      - path: /path/to/$os/$target/environment
        optional: true
@@ -700,11 +701,11 @@ with the ``optional`` clause and conditional with the ``when`` clause. (See
 
 Files are listed using paths to individual files or directories containing them.
 Path entries may be absolute or relative to the environment or specified as 
-URLs. URLs to individual files need link to the **raw** form of the file's 
+URLs. URLs to individual files must link to the **raw** form of the file's 
 contents (e.g., `GitHub
 <https://docs.github.com/en/repositories/working-with-files/using-files/viewing-and-understanding-files#viewing-or-copying-the-raw-file-content>`_ 
 or `GitLab
-<https://docs.gitlab.com/ee/api/repository_files.html#get-raw-file-from-repository>`_).
+<https://docs.gitlab.com/ee/api/repository_files.html#get-raw-file-from-repository>`_) **and** include a valid sha256 for the file.
 Only the ``file``, ``ftp``, ``http`` and ``https`` protocols (or schemes) are
 supported. Spack-specific, environment and user path variables can be used.
 (See :ref:`config-file-variables` for more information.)
@@ -999,6 +1000,28 @@ For example, the following environment has three root packages:
 This allows for a much-needed reduction in redundancy between packages
 and constraints.
 
+-------------------------------
+Modifying Environment Variables
+-------------------------------
+
+Spack Environments can modify the active shell's environment variables when activated.  The environment can be
+configured to set, unset, prepend, or append using ``env_vars`` configuration in the ``spack.yaml``  or through config scopes
+file:
+
+.. code-block:: yaml
+
+  spack:
+    env_vars:
+      set:
+        ENVAR_TO_SET_IN_ENV_LOAD: "FOO"
+      unset:
+        ENVAR_TO_UNSET_IN_ENV_LOAD:
+      prepend_path:
+        PATH_LIST: "path/to/prepend"
+      append_path:
+        PATH_LIST: "path/to/append"
+      remove_path:
+        PATH_LIST: "path/to/remove"
 
 -----------------
 Environment Views

lib/spack/docs/example_files/spack.yaml

@@ -1,161 +0,0 @@
-spack:
-  definitions:
-  - compiler-pkgs:
-    - 'llvm+clang@6.0.1 os=centos7'
-    - 'gcc@6.5.0 os=centos7'
-    - 'llvm+clang@6.0.1 os=ubuntu18.04'
-    - 'gcc@6.5.0 os=ubuntu18.04'
-  - pkgs:
-    - readline@7.0
-    # - xsdk@0.4.0
-  - compilers:
-    - '%gcc@5.5.0'
-    - '%gcc@6.5.0'
-    - '%gcc@7.3.0'
-    - '%clang@6.0.0'
-    - '%clang@6.0.1'
-  - oses:
-    - os=ubuntu18.04
-    - os=centos7
-
-  specs:
-  - matrix:
-    - [$pkgs]
-    - [$compilers]
-    - [$oses]
-    exclude:
-      - '%gcc@7.3.0 os=centos7'
-      - '%gcc@5.5.0 os=ubuntu18.04'
-
-  mirrors:
-    cloud_gitlab: https://mirror.spack.io
-
-  compilers:
-    # The .gitlab-ci.yml for this project picks a Docker container which does
-    # not have any compilers pre-built and ready to use, so we need to fake the
-    # existence of those here.
-    - compiler:
-        operating_system: centos7
-        modules: []
-        paths:
-          cc: /not/used
-          cxx: /not/used
-          f77: /not/used
-          fc: /not/used
-        spec: gcc@5.5.0
-        target: x86_64
-    - compiler:
-        operating_system: centos7
-        modules: []
-        paths:
-          cc: /not/used
-          cxx: /not/used
-          f77: /not/used
-          fc: /not/used
-        spec: gcc@6.5.0
-        target: x86_64
-    - compiler:
-        operating_system: centos7
-        modules: []
-        paths:
-          cc: /not/used
-          cxx: /not/used
-          f77: /not/used
-          fc: /not/used
-        spec: clang@6.0.0
-        target: x86_64
-    - compiler:
-        operating_system: centos7
-        modules: []
-        paths:
-          cc: /not/used
-          cxx: /not/used
-          f77: /not/used
-          fc: /not/used
-        spec: clang@6.0.1
-        target: x86_64
-
-    - compiler:
-        operating_system: ubuntu18.04
-        modules: []
-        paths:
-          cc: /not/used
-          cxx: /not/used
-          f77: /not/used
-          fc: /not/used
-        spec: clang@6.0.0
-        target: x86_64
-    - compiler:
-        operating_system: ubuntu18.04
-        modules: []
-        paths:
-          cc: /not/used
-          cxx: /not/used
-          f77: /not/used
-          fc: /not/used
-        spec: clang@6.0.1
-        target: x86_64
-    - compiler:
-        operating_system: ubuntu18.04
-        modules: []
-        paths:
-          cc: /not/used
-          cxx: /not/used
-          f77: /not/used
-          fc: /not/used
-        spec: gcc@6.5.0
-        target: x86_64
-    - compiler:
-        operating_system: ubuntu18.04
-        modules: []
-        paths:
-          cc: /not/used
-          cxx: /not/used
-          f77: /not/used
-          fc: /not/used
-        spec: gcc@7.3.0
-        target: x86_64
-
-  gitlab-ci:
-    bootstrap:
-      - name: compiler-pkgs
-        compiler-agnostic: true
-    mappings:
-      - # spack-cloud-ubuntu
-        match:
-          # these are specs, if *any* match the spec under consideration, this
-          # 'mapping' will be used to generate the CI job
-          - os=ubuntu18.04
-        runner-attributes:
-          # 'tags' and 'image' go directly onto the job, 'variables' will
-          # be added to what we already necessarily create for the job as
-          # a part of the CI workflow
-          tags:
-            - spack-k8s
-          image:
-            name: scottwittenburg/spack_builder_ubuntu_18.04
-            entrypoint: [""]
-      - # spack-cloud-centos
-        match:
-          # these are specs, if *any* match the spec under consideration, this
-          # 'mapping' will be used to generate the CI job
-          - 'os=centos7'
-        runner-attributes:
-          tags:
-            - spack-k8s
-          image:
-            name: scottwittenburg/spack_builder_centos_7
-            entrypoint: [""]
-
-  cdash:
-    build-group: Release Testing
-    url: http://cdash
-    project: Spack Testing
-    site: Spack Docker-Compose Workflow
-
-  repos: []
-  upstreams: {}
-  modules:
-    enable: []
-  packages: {}
-  config: {}

lib/spack/docs/features.rst

@@ -131,7 +131,7 @@ creates a simple python file:
 It doesn't take much python coding to get from there to a working
 package:
 
-.. literalinclude:: _spack_root/var/spack/repos/builtin/packages/libelf/package.py
+.. literalinclude:: _spack_root/var/spack/repos/spack_repo/builtin/packages/libelf/package.py
    :lines: 5-
 
 Spack also provides wrapper functions around common commands like

lib/spack/docs/getting_started.rst

@@ -254,12 +254,11 @@ directory.
 Compiler configuration
 ----------------------
 
-Spack has the ability to build packages with multiple compilers and
-compiler versions. Compilers can be made available to Spack by
-specifying them manually in ``compilers.yaml`` or ``packages.yaml``,
-or automatically by running ``spack compiler find``, but for
-convenience Spack will automatically detect compilers the first time
-it needs them.
+Spack has the ability to build packages with multiple compilers and compiler versions.
+Compilers can be made available to Spack by specifying them manually in ``packages.yaml``,
+or automatically by running ``spack compiler find``.
+For convenience, Spack will automatically detect compilers the first time it needs them,
+if none is available.
 
 .. _cmd-spack-compilers:
 
@@ -274,16 +273,11 @@ compilers`` or ``spack compiler list``:
 
    $ spack compilers
    ==> Available compilers
-   -- gcc ---------------------------------------------------------
-       gcc@4.9.0  gcc@4.8.0  gcc@4.7.0  gcc@4.6.2  gcc@4.4.7
-       gcc@4.8.2  gcc@4.7.1  gcc@4.6.3  gcc@4.6.1  gcc@4.1.2
-   -- intel -------------------------------------------------------
-       intel@15.0.0  intel@14.0.0  intel@13.0.0  intel@12.1.0  intel@10.0
-       intel@14.0.3  intel@13.1.1  intel@12.1.5  intel@12.0.4  intel@9.1
-       intel@14.0.2  intel@13.1.0  intel@12.1.3  intel@11.1
-       intel@14.0.1  intel@13.0.1  intel@12.1.2  intel@10.1
-   -- clang -------------------------------------------------------
-       clang@3.4  clang@3.3  clang@3.2  clang@3.1
+   -- gcc ubuntu20.04-x86_64 ---------------------------------------
+   gcc@9.4.0  gcc@8.4.0  gcc@10.5.0
+
+   -- llvm ubuntu20.04-x86_64 --------------------------------------
+   llvm@12.0.0  llvm@11.0.0  llvm@10.0.0
 
 Any of these compilers can be used to build Spack packages.  More on
 how this is done is in :ref:`sec-specs`.
@@ -302,16 +296,22 @@ An alias for ``spack compiler find``.
 ``spack compiler find``
 ^^^^^^^^^^^^^^^^^^^^^^^
 
-Lists the compilers currently available to Spack. If you do not see
-a compiler in this list, but you want to use it with Spack, you can
-simply run ``spack compiler find`` with the path to where the
-compiler is installed.  For example:
+If you do not see a compiler in the list shown by:
 
 .. code-block:: console
 
-   $ spack compiler find /usr/local/tools/ic-13.0.079
-   ==> Added 1 new compiler to ~/.spack/linux/compilers.yaml
-       intel@13.0.079
+   $ spack compiler list
+
+but you want to use it with Spack, you can simply run ``spack compiler find`` with the
+path to where the compiler is installed.  For example:
+
+.. code-block:: console
+
+   $ spack compiler find /opt/intel/oneapi/compiler/2025.1/bin/
+   ==> Added 1 new compiler to /home/user/.spack/packages.yaml
+       intel-oneapi-compilers@2025.1.0
+   ==> Compilers are defined in the following files:
+       /home/user/.spack/packages.yaml
 
 Or you can run ``spack compiler find`` with no arguments to force
 auto-detection.  This is useful if you do not know where compilers are
@@ -322,7 +322,7 @@ installed, but you know that new compilers have been added to your
 
    $ module load gcc/4.9.0
    $ spack compiler find
-   ==> Added 1 new compiler to ~/.spack/linux/compilers.yaml
+   ==> Added 1 new compiler to /home/user/.spack/packages.yaml
        gcc@4.9.0
 
 This loads the environment module for gcc-4.9.0 to add it to
@@ -331,7 +331,7 @@ This loads the environment module for gcc-4.9.0 to add it to
 .. note::
 
    By default, spack does not fill in the ``modules:`` field in the
-   ``compilers.yaml`` file.  If you are using a compiler from a
+   ``packages.yaml`` file.  If you are using a compiler from a
    module, then you should add this field manually.
    See the section on :ref:`compilers-requiring-modules`.
 
@@ -341,91 +341,82 @@ This loads the environment module for gcc-4.9.0 to add it to
 ``spack compiler info``
 ^^^^^^^^^^^^^^^^^^^^^^^
 
-If you want to see specifics on a particular compiler, you can run
-``spack compiler info`` on it:
+If you want to see additional information on some specific compilers, you can run ``spack compiler info`` on it:
 
 .. code-block:: console
 
-   $ spack compiler info intel@15
-   intel@15.0.0:
-     paths:
-       cc  = /usr/local/bin/icc-15.0.090
-       cxx = /usr/local/bin/icpc-15.0.090
-       f77 = /usr/local/bin/ifort-15.0.090
-       fc  = /usr/local/bin/ifort-15.0.090
-     modules = []
-     operating_system = centos6
-   ...
+   $ spack compiler info gcc
+   gcc@=8.4.0 languages='c,c++,fortran' arch=linux-ubuntu20.04-x86_64:
+     prefix: /usr
+     compilers:
+       c: /usr/bin/gcc-8
+       cxx: /usr/bin/g++-8
+       fortran: /usr/bin/gfortran-8
 
-This shows which C, C++, and Fortran compilers were detected by Spack.
-Notice also that we didn't have to be too specific about the
-version. We just said ``intel@15``, and information about the only
-matching Intel compiler was displayed.
+   gcc@=9.4.0 languages='c,c++,fortran' arch=linux-ubuntu20.04-x86_64:
+     prefix: /usr
+     compilers:
+       c: /usr/bin/gcc
+       cxx: /usr/bin/g++
+       fortran: /usr/bin/gfortran
+
+   gcc@=10.5.0 languages='c,c++,fortran' arch=linux-ubuntu20.04-x86_64:
+     prefix: /usr
+     compilers:
+       c: /usr/bin/gcc-10
+       cxx: /usr/bin/g++-10
+       fortran: /usr/bin/gfortran-10
+
+This shows the details of the compilers that were detected by Spack.
+Notice also that we didn't have to be too specific about the version. We just said ``gcc``, and we got information
+about all the matching compilers.
 
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 Manual compiler configuration
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-If auto-detection fails, you can manually configure a compiler by
-editing your ``~/.spack/<platform>/compilers.yaml`` file.  You can do this by running
-``spack config edit compilers``, which will open the file in
+If auto-detection fails, you can manually configure a compiler by editing your ``~/.spack/packages.yaml`` file.
+You can do this by running ``spack config edit packages``, which will open the file in
 :ref:`your favorite editor <controlling-the-editor>`.
 
-Each compiler configuration in the file looks like this:
+Each compiler has an "external" entry in the file with some ``extra_attributes``:
 
 .. code-block:: yaml
 
-   compilers:
-   - compiler:
-       modules: []
-       operating_system: centos6
-       paths:
-         cc: /usr/local/bin/icc-15.0.024-beta
-         cxx: /usr/local/bin/icpc-15.0.024-beta
-         f77: /usr/local/bin/ifort-15.0.024-beta
-         fc: /usr/local/bin/ifort-15.0.024-beta
-       spec: intel@15.0.0
+   packages:
+     gcc:
+       externals:
+       - spec: gcc@10.5.0 languages='c,c++,fortran'
+         prefix: /usr
+         extra_attributes:
+           compilers:
+             c: /usr/bin/gcc-10
+             cxx: /usr/bin/g++-10
+             fortran: /usr/bin/gfortran-10
 
-For compilers that do not support Fortran (like ``clang``), put
-``None`` for ``f77`` and ``fc``:
+The compiler executables are listed under ``extra_attributes:compilers``, and are keyed by language.
+Once you save the file, the configured compilers will show up in the list displayed by ``spack compilers``.
 
-.. code-block:: yaml
-
-   compilers:
-   - compiler:
-       modules: []
-       operating_system: centos6
-       paths:
-         cc: /usr/bin/clang
-         cxx: /usr/bin/clang++
-         f77: None
-         fc: None
-       spec: clang@3.3svn
-
-Once you save the file, the configured compilers will show up in the
-list displayed by ``spack compilers``.
-
-You can also add compiler flags to manually configured compilers. These
-flags should be specified in the ``flags`` section of the compiler
-specification. The valid flags are ``cflags``, ``cxxflags``, ``fflags``,
+You can also add compiler flags to manually configured compilers. These flags should be specified in the
+``flags`` section of the compiler specification. The valid flags are ``cflags``, ``cxxflags``, ``fflags``,
 ``cppflags``, ``ldflags``, and ``ldlibs``. For example:
 
 .. code-block:: yaml
 
-   compilers:
-   - compiler:
-       modules: []
-       operating_system: centos6
-       paths:
-         cc: /usr/bin/gcc
-         cxx: /usr/bin/g++
-         f77: /usr/bin/gfortran
-         fc: /usr/bin/gfortran
-       flags:
-         cflags: -O3 -fPIC
-         cxxflags: -O3 -fPIC
-         cppflags: -O3 -fPIC
-       spec: gcc@4.7.2
+   packages:
+     gcc:
+       externals:
+       - spec: gcc@10.5.0 languages='c,c++,fortran'
+         prefix: /usr
+         extra_attributes:
+           compilers:
+             c: /usr/bin/gcc-10
+             cxx: /usr/bin/g++-10
+             fortran: /usr/bin/gfortran-10
+           flags:
+             cflags: -O3 -fPIC
+             cxxflags: -O3 -fPIC
+             cppflags: -O3 -fPIC
 
 These flags will be treated by spack as if they were entered from
 the command line each time this compiler is used. The compiler wrappers
@@ -440,95 +431,44 @@ These variables should be specified in the ``environment`` section of the compil
 specification. The operations available to modify the environment are ``set``, ``unset``,
 ``prepend_path``, ``append_path``, and ``remove_path``. For example:
 
-.. code-block:: yaml
-
-   compilers:
-   - compiler:
-       modules: []
-       operating_system: centos6
-       paths:
-         cc: /opt/intel/oneapi/compiler/latest/linux/bin/icx
-         cxx: /opt/intel/oneapi/compiler/latest/linux/bin/icpx
-         f77: /opt/intel/oneapi/compiler/latest/linux/bin/ifx
-         fc: /opt/intel/oneapi/compiler/latest/linux/bin/ifx
-       spec: oneapi@latest
-       environment:
-         set:
-           MKL_ROOT: "/path/to/mkl/root"
-         unset: # A list of environment variables to unset
-           - CC
-         prepend_path: # Similar for append|remove_path
-           LD_LIBRARY_PATH: /ld/paths/added/by/setvars/sh
-
-.. note::
-
-   Spack is in the process of moving compilers from a separate
-   attribute to be handled like all other packages. As part of this
-   process, the ``compilers.yaml`` section will eventually be replaced
-   by configuration in the ``packages.yaml`` section. This new
-   configuration is now available, although it is not yet the default
-   behavior.
-
-Compilers can also be configured as external packages in the
-``packages.yaml`` config file. Any external package for a compiler
-(e.g. ``gcc`` or ``llvm``) will be treated as a configured compiler
-assuming the paths to the compiler executables are determinable from
-the prefix.
-
-If the paths to the compiler executable are not determinable from the
-prefix, you can add them to the ``extra_attributes`` field. Similarly,
-all other fields from the compilers config can be added to the
-``extra_attributes`` field for an external representing a compiler.
-
-Note that the format for the ``paths`` field in the
-``extra_attributes`` section is different than in the ``compilers``
-config. For compilers configured as external packages, the section is
-named ``compilers`` and the dictionary maps language names (``c``,
-``cxx``, ``fortran``) to paths, rather than using the names ``cc``,
-``fc``, and ``f77``.
-
 .. code-block:: yaml
 
    packages:
-     gcc:
-       external:
-       - spec: gcc@12.2.0 arch=linux-rhel8-skylake
-         prefix: /usr
-         extra_attributes:
-           environment:
-             set:
-               GCC_ROOT: /usr
-       external:
-       - spec: llvm+clang@15.0.0 arch=linux-rhel8-skylake
-         prefix: /usr
+     intel-oneapi-compilers:
+       externals:
+       - spec: intel-oneapi-compilers@2025.1.0
+         prefix: /opt/intel/oneapi
          extra_attributes:
            compilers:
-             c: /usr/bin/clang-with-suffix
-             cxx: /usr/bin/clang++-with-extra-info
-             fortran: /usr/bin/gfortran
-           extra_rpaths:
-           - /usr/lib/llvm/
+             c: /opt/intel/oneapi/compiler/2025.1/bin/icx
+             cxx: /opt/intel/oneapi/compiler/2025.1/bin/icpx
+             fortran: /opt/intel/oneapi/compiler/2025.1/bin/ifx
+           environment:
+             set:
+               MKL_ROOT: "/path/to/mkl/root"
+             unset: # A list of environment variables to unset
+               - CC
+             prepend_path: # Similar for append|remove_path
+               LD_LIBRARY_PATH: /ld/paths/added/by/setvars/sh
 
 ^^^^^^^^^^^^^^^^^^^^^^^
 Build Your Own Compiler
 ^^^^^^^^^^^^^^^^^^^^^^^
 
-If you are particular about which compiler/version you use, you might
-wish to have Spack build it for you.  For example:
+If you are particular about which compiler/version you use, you might wish to have Spack build it for you.
+For example:
 
 .. code-block:: console
 
-   $ spack install gcc@4.9.3
+   $ spack install gcc@14+binutils
 
-Once that has finished, you will need to add it to your
-``compilers.yaml`` file.  You can then set Spack to use it by default
-by adding the following to your ``packages.yaml`` file:
+Once the compiler is installed, you can start using it without additional configuration:
 
-.. code-block:: yaml
+.. code-block:: console
 
-   packages:
-     all:
-       compiler: [gcc@4.9.3]
+   $ spack install hdf5~mpi %gcc@14
+
+The same holds true for compilers that are made available from buildcaches, when reusing them is allowed.
 
 .. _compilers-requiring-modules:
 
@@ -536,30 +476,26 @@ by adding the following to your ``packages.yaml`` file:
 Compilers Requiring Modules
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-Many installed compilers will work regardless of the environment they
-are called with.  However, some installed compilers require
-``$LD_LIBRARY_PATH`` or other environment variables to be set in order
-to run; this is typical for Intel and other proprietary compilers.
+Many installed compilers will work regardless of the environment they are called with.
+However, some installed compilers require environment variables to be set in order to run;
+this is typical for Intel and other proprietary compilers.
 
-In such a case, you should tell Spack which module(s) to load in order
-to run the chosen compiler (If the compiler does not come with a
-module file, you might consider making one by hand).  Spack will load
-this module into the environment ONLY when the compiler is run, and
-NOT in general for a package's ``install()`` method.  See, for
-example, this ``compilers.yaml`` file:
+On typical HPC clusters, these environment modifications are usually delegated to some "module" system.
+In such a case, you should tell Spack which module(s) to load in order to run the chosen compiler:
 
 .. code-block:: yaml
 
-   compilers:
-   - compiler:
-       modules: [other/comp/gcc-5.3-sp3]
-       operating_system: SuSE11
-       paths:
-         cc: /usr/local/other/SLES11.3/gcc/5.3.0/bin/gcc
-         cxx: /usr/local/other/SLES11.3/gcc/5.3.0/bin/g++
-         f77: /usr/local/other/SLES11.3/gcc/5.3.0/bin/gfortran
-         fc: /usr/local/other/SLES11.3/gcc/5.3.0/bin/gfortran
-       spec: gcc@5.3.0
+   packages:
+     gcc:
+       externals:
+       - spec: gcc@10.5.0 languages='c,c++,fortran'
+         prefix: /opt/compilers
+         extra_attributes:
+           compilers:
+             c: /opt/compilers/bin/gcc-10
+             cxx: /opt/compilers/bin/g++-10
+             fortran: /opt/compilers/bin/gfortran-10
+         modules: [gcc/10.5.0]
 
 Some compilers require special environment settings to be loaded not just
 to run, but also to execute the code they build, breaking packages that
@@ -580,7 +516,7 @@ Licensed Compilers
 ^^^^^^^^^^^^^^^^^^
 
 Some proprietary compilers require licensing to use.  If you need to
-use a licensed compiler (eg, PGI), the process is similar to a mix of
+use a licensed compiler, the process is similar to a mix of
 build your own, plus modules:
 
 #. Create a Spack package (if it doesn't exist already) to install
@@ -590,24 +526,21 @@ build your own, plus modules:
    using Spack to load the module it just created, and running simple
    builds (eg: ``cc helloWorld.c && ./a.out``)
 
-#. Add the newly-installed compiler to ``compilers.yaml`` as shown
-   above.
+#. Add the newly-installed compiler to ``packages.yaml`` as shown above.
 
 .. _mixed-toolchains:
 
-^^^^^^^^^^^^^^^^
-Mixed Toolchains
-^^^^^^^^^^^^^^^^
+^^^^^^^^^^^^^^^^^^^^^^^^^^
+Fortran compilers on macOS
+^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 Modern compilers typically come with related compilers for C, C++ and
 Fortran bundled together.  When possible, results are best if the same
 compiler is used for all languages.
 
-In some cases, this is not possible.  For example, starting with macOS El
-Capitan (10.11), many packages no longer build with GCC, but XCode
-provides no Fortran compilers.  The user is therefore forced to use a
-mixed toolchain: XCode-provided Clang for C/C++ and GNU ``gfortran`` for
-Fortran.
+In some cases, this is not possible.  For example, XCode on macOS provides no Fortran compilers.
+The user is therefore forced to use a mixed toolchain: XCode-provided Clang for C/C++ and e.g.
+GNU ``gfortran`` for Fortran.
 
 #. You need to make sure that Xcode is installed. Run the following command:
 
@@ -660,45 +593,25 @@ Fortran.
 
    Note: the flag is ``-license``, not ``--license``.
 
-#. Run ``spack compiler find`` to locate Clang.
-
 #. There are different ways to get ``gfortran`` on macOS. For example, you can
    install GCC with Spack (``spack install gcc``), with Homebrew (``brew install
    gcc``), or from a `DMG installer
    <https://github.com/fxcoudert/gfortran-for-macOS/releases>`_.
 
-#. The only thing left to do is to edit ``~/.spack/darwin/compilers.yaml`` to provide
-   the path to ``gfortran``:
+#. Run ``spack compiler find`` to locate both Apple-Clang and GCC.
 
-   .. code-block:: yaml
-
-      compilers:
-      - compiler:
-        # ...
-        paths:
-          cc: /usr/bin/clang
-          cxx: /usr/bin/clang++
-          f77: /path/to/bin/gfortran
-          fc: /path/to/bin/gfortran
-        spec: apple-clang@11.0.0
-
-
-   If you used Spack to install GCC, you can get the installation prefix by
-   ``spack location -i gcc`` (this will only work if you have a single version
-   of GCC installed). Whereas for Homebrew, GCC is installed in
-   ``/usr/local/Cellar/gcc/x.y.z``. With the DMG installer, the correct path
-   will be ``/usr/local/gfortran``.
+Since languages in Spack are modeled as virtual packages, ``apple-clang`` will be used to provide
+C and C++, while GCC will be used for Fortran.
 
 ^^^^^^^^^^^^^^^^^^^^^
 Compiler Verification
 ^^^^^^^^^^^^^^^^^^^^^
 
-You can verify that your compilers are configured properly by installing a
-simple package.  For example:
+You can verify that your compilers are configured properly by installing a simple package. For example:
 
 .. code-block:: console
 
-   $ spack install zlib%gcc@5.3.0
+   $ spack install zlib-ng%gcc@5.3.0
 
 
 .. _vendor-specific-compiler-configuration:
@@ -707,9 +620,7 @@ simple package.  For example:
 Vendor-Specific Compiler Configuration
 --------------------------------------
 
-With Spack, things usually "just work" with GCC.  Not so for other
-compilers.  This section provides details on how to get specific
-compilers working.
+This section provides details on how to get vendor-specific compilers working.
 
 ^^^^^^^^^^^^^^^
 Intel Compilers
@@ -731,8 +642,8 @@ compilers:
       you have installed from the ``PATH`` environment variable.
 
       If you want use a version of ``gcc`` or ``g++`` other than the default
-      version on your system, you need to use either the ``-gcc-name``
-      or ``-gxx-name`` compiler option to specify the path to the version of
+      version on your system, you need to use either the ``--gcc-install-dir``
+      or ``--gcc-toolchain`` compiler option to specify the path to the version of
       ``gcc`` or ``g++`` that you want to use."
 
       -- `Intel Reference Guide <https://software.intel.com/en-us/node/522750>`_
@@ -740,76 +651,12 @@ compilers:
 Intel compilers may therefore be configured in one of two ways with
 Spack: using modules, or using compiler flags.
 
-""""""""""""""""""""""""""
-Configuration with Modules
-""""""""""""""""""""""""""
-
-One can control which GCC is seen by the Intel compiler with modules.
-A module must be loaded both for the Intel Compiler (so it will run)
-and GCC (so the compiler can find the intended GCC).  The following
-configuration in ``compilers.yaml`` illustrates this technique:
-
-.. code-block:: yaml
-
-   compilers:
-   - compiler:
-       modules: [gcc-4.9.3, intel-15.0.24]
-       operating_system: centos7
-       paths:
-         cc: /opt/intel-15.0.24/bin/icc-15.0.24-beta
-         cxx: /opt/intel-15.0.24/bin/icpc-15.0.24-beta
-         f77: /opt/intel-15.0.24/bin/ifort-15.0.24-beta
-         fc: /opt/intel-15.0.24/bin/ifort-15.0.24-beta
-       spec: intel@15.0.24.4.9.3
-
-
-.. note::
-
-   The version number on the Intel compiler is a combination of
-   the "native" Intel version number and the GNU compiler it is
-   targeting.
-
-""""""""""""""""""""""""""
-Command Line Configuration
-""""""""""""""""""""""""""
-
-One can also control which GCC is seen by the Intel compiler by adding
-flags to the ``icc`` command:
-
-#. Identify the location of the compiler you just installed:
-
-   .. code-block:: console
-
-       $ spack location --install-dir gcc
-       ~/spack/opt/spack/linux-centos7-x86_64/gcc-4.9.3-iy4rw...
-
-#. Set up ``compilers.yaml``, for example:
-
-   .. code-block:: yaml
-
-       compilers:
-       - compiler:
-           modules: [intel-15.0.24]
-           operating_system: centos7
-           paths:
-             cc: /opt/intel-15.0.24/bin/icc-15.0.24-beta
-             cxx: /opt/intel-15.0.24/bin/icpc-15.0.24-beta
-             f77: /opt/intel-15.0.24/bin/ifort-15.0.24-beta
-             fc: /opt/intel-15.0.24/bin/ifort-15.0.24-beta
-           flags:
-             cflags: -gcc-name ~/spack/opt/spack/linux-centos7-x86_64/gcc-4.9.3-iy4rw.../bin/gcc
-             cxxflags: -gxx-name ~/spack/opt/spack/linux-centos7-x86_64/gcc-4.9.3-iy4rw.../bin/g++
-             fflags: -gcc-name ~/spack/opt/spack/linux-centos7-x86_64/gcc-4.9.3-iy4rw.../bin/gcc
-           spec: intel@15.0.24.4.9.3
-
-
 ^^^
 NAG
 ^^^
 
-The Numerical Algorithms Group provides a licensed Fortran compiler. Like Clang,
-this requires you to set up a :ref:`mixed-toolchains`. It is recommended to use
-GCC for your C/C++ compilers.
+The Numerical Algorithms Group provides a licensed Fortran compiler.
+It is recommended to use GCC for your C/C++ compilers.
 
 The NAG Fortran compilers are a bit more strict than other compilers, and many
 packages will fail to install with error messages like:
@@ -826,44 +673,40 @@ the command line:
 
    $ spack install openmpi fflags="-mismatch"
 
-Or it can be set permanently in your ``compilers.yaml``:
+Or it can be set permanently in your ``packages.yaml``:
 
 .. code-block:: yaml
 
-   - compiler:
-    modules: []
-    operating_system: centos6
-    paths:
-      cc: /soft/spack/opt/spack/linux-x86_64/gcc-5.3.0/gcc-6.1.0-q2zosj3igepi3pjnqt74bwazmptr5gpj/bin/gcc
-      cxx: /soft/spack/opt/spack/linux-x86_64/gcc-5.3.0/gcc-6.1.0-q2zosj3igepi3pjnqt74bwazmptr5gpj/bin/g++
-      f77: /soft/spack/opt/spack/linux-x86_64/gcc-4.4.7/nag-6.1-jt3h5hwt5myezgqguhfsan52zcskqene/bin/nagfor
-      fc: /soft/spack/opt/spack/linux-x86_64/gcc-4.4.7/nag-6.1-jt3h5hwt5myezgqguhfsan52zcskqene/bin/nagfor
-    flags:
-      fflags: -mismatch
-    spec: nag@6.1
-
+   packages:
+     nag:
+       externals:
+       - spec: nag@6.1
+         prefix: /opt/nag/bin
+         extra_attributes:
+           compilers:
+             fortran: /opt/nag/bin/nagfor
+         flags:
+           fflags: -mismatch
 
 ---------------
 System Packages
 ---------------
 
-Once compilers are configured, one needs to determine which
-pre-installed system packages, if any, to use in builds.  This is
-configured in the file ``~/.spack/packages.yaml``.  For example, to use
-an OpenMPI installed in /opt/local, one would use:
+Once compilers are configured, one needs to determine which pre-installed system packages,
+if any, to use in builds.  These are also configured in the ``~/.spack/packages.yaml`` file.
+For example, to use an OpenMPI installed in /opt/local, one would use:
 
 .. code-block:: yaml
 
-    packages:
-        openmpi:
-            externals:
-            - spec: openmpi@1.10.1
-              prefix: /opt/local
-            buildable: False
+   packages:
+     openmpi:
+       buildable: False
+       externals:
+       - spec: openmpi@1.10.1
+         prefix: /opt/local
 
-In general, Spack is easier to use and more reliable if it builds all of
-its own dependencies.  However, there are several packages for which one
-commonly needs to use system versions:
+In general, *Spack is easier to use and more reliable if it builds all of its own dependencies*.
+However, there are several packages for which one commonly needs to use system versions:
 
 ^^^
 MPI
@@ -876,8 +719,7 @@ you are unlikely to get a working MPI from Spack.  Instead, use an
 appropriate pre-installed MPI.
 
 If you choose a pre-installed MPI, you should consider using the
-pre-installed compiler used to build that MPI; see above on
-``compilers.yaml``.
+pre-installed compiler used to build that MPI.
 
 ^^^^^^^
 OpenSSL
@@ -1441,9 +1283,9 @@ To configure Spack, first run the following command inside the Spack console:
    spack compiler find
 
 This creates a ``.staging`` directory in our Spack prefix, along with a ``windows`` subdirectory
-containing a ``compilers.yaml`` file. On a fresh Windows install with the above packages
+containing a ``packages.yaml`` file. On a fresh Windows install with the above packages
 installed, this command should only detect Microsoft Visual Studio and the Intel Fortran
-compiler will be integrated within the first version of MSVC present in the ``compilers.yaml``
+compiler will be integrated within the first version of MSVC present in the ``packages.yaml``
 output.
 
 Spack provides a default ``config.yaml`` file for Windows that it will use unless overridden.

lib/spack/docs/gpu_configuration.rst

@@ -23,7 +23,6 @@ components for use by dependent packages:
 
    packages:
      all:
-       compiler: [rocmcc@=5.3.0]
        variants: amdgpu_target=gfx90a
      hip:
        buildable: false
@@ -70,16 +69,15 @@ This is in combination with the following compiler definition:
 
 .. code-block:: yaml
 
-   compilers:
-   - compiler:
-       spec: rocmcc@=5.3.0
-       paths:
-         cc: /opt/rocm-5.3.0/bin/amdclang
-         cxx: /opt/rocm-5.3.0/bin/amdclang++
-         f77: null
-         fc: /opt/rocm-5.3.0/bin/amdflang
-       operating_system: rhel8
-       target: x86_64
+   packages:
+     llvm-amdgpu:
+       externals:
+       - spec: llvm-amdgpu@=5.3.0
+         prefix: /opt/rocm-5.3.0
+         compilers:
+           c: /opt/rocm-5.3.0/bin/amdclang
+           cxx: /opt/rocm-5.3.0/bin/amdclang++
+           fortran: null
 
 This includes the following considerations:
 

lib/spack/docs/include_yaml.rst

@@ -43,6 +43,20 @@ or specified as URLs. Only the ``file``, ``ftp``, ``http`` and ``https`` protoco
 schemes) are supported. Spack-specific, environment and user path variables
 can be used. (See :ref:`config-file-variables` for more information.)
 
+A ``sha256`` is required for remote file URLs and must be specified as follows:
+
+.. code-block:: yaml
+
+   include:
+   - path: https://github.com/path/to/raw/config/compilers.yaml
+     sha256: 26e871804a92cd07bb3d611b31b4156ae93d35b6a6d6e0ef3a67871fcb1d258b
+
+Additionally, remote file URLs must link to the **raw** form of the file's
+contents (e.g., `GitHub
+<https://docs.github.com/en/repositories/working-with-files/using-files/viewing-and-understanding-files#viewing-or-copying-the-raw-file-content>`_
+or `GitLab
+<https://docs.gitlab.com/ee/api/repository_files.html#get-raw-file-from-repository>`_).
+
 .. warning::
 
    Recursive includes are not currently processed in a breadth-first manner

lib/spack/docs/index.rst

@@ -75,6 +75,7 @@ or refer to the full manual below.
    packages_yaml
    build_settings
    environments
+   env_vars_yaml
    containers
    mirrors
    module_file_support

lib/spack/docs/module_file_support.rst

@@ -128,7 +128,7 @@ depend on the spec:
 
 .. code-block:: python
 
-   def setup_run_environment(self, env):
+   def setup_run_environment(self, env: EnvironmentModifications) -> None:
        if self.spec.satisfies("+foo"):
            env.set("FOO", "bar")
 
@@ -142,7 +142,7 @@ For example, a simplified version of the ``python`` package could look like this
 
 .. code-block:: python
 
-   def setup_dependent_run_environment(self, env, dependent_spec):
+   def setup_dependent_run_environment(self, env: EnvironmentModifications, dependent_spec: Spec) -> None:
        if dependent_spec.package.extends(self.spec):
            env.prepend_path("PYTHONPATH", dependent_spec.prefix.lib.python)
 

lib/spack/docs/packages_yaml.rst

@@ -557,14 +557,13 @@ preferences.
    FAQ: :ref:`Why does Spack pick particular versions and variants? <faq-concretizer-precedence>`
 
 
-Most package preferences (``compilers``, ``target`` and ``providers``)
+The ``target`` and ``providers`` preferences
 can only be set globally under the ``all`` section of ``packages.yaml``:
 
 .. code-block:: yaml
 
    packages:
      all:
-       compiler: [gcc@12.2.0, clang@12:, oneapi@2023:]
        target: [x86_64_v3]
        providers:
          mpi: [mvapich2, mpich, openmpi]

lib/spack/docs/packaging_guide.rst

@@ -369,9 +369,9 @@ If you have a collection of software expected to work well together with
 no source code of its own, you can create a :ref:`BundlePackage <bundlepackage>`.
 Examples where bundle packages can be useful include defining suites of
 applications (e.g, `EcpProxyApps
-<https://github.com/spack/spack/blob/develop/var/spack/repos/builtin/packages/ecp-proxy-apps/package.py>`_), commonly used libraries
-(e.g., `AmdAocl <https://github.com/spack/spack/blob/develop/var/spack/repos/builtin/packages/amd-aocl/package.py>`_),
-and software development kits (e.g., `EcpDataVisSdk <https://github.com/spack/spack/blob/develop/var/spack/repos/builtin/packages/ecp-data-vis-sdk/package.py>`_).
+<https://github.com/spack/spack/blob/develop/var/spack/repos/spack_repo/builtin/packages/ecp_proxy_apps/package.py>`_), commonly used libraries
+(e.g., `AmdAocl <https://github.com/spack/spack/blob/develop/var/spack/repos/spack_repo/builtin/packages/amd_aocl/package.py>`_),
+and software development kits (e.g., `EcpDataVisSdk <https://github.com/spack/spack/blob/develop/var/spack/repos/spack_repo/builtin/packages/ecp_data_vis_sdk/package.py>`_).
 
 These versioned packages primarily consist of dependencies on the associated
 software packages. They can include :ref:`variants <variants>` to ensure
@@ -443,7 +443,7 @@ lives in:
 .. code-block:: console
 
    $ spack location -p gmp
-   ${SPACK_ROOT}/var/spack/repos/builtin/packages/gmp/package.py
+   ${SPACK_ROOT}/var/spack/repos/spack_repo/builtin/packages/gmp/package.py
 
 but ``spack edit`` provides a much simpler shortcut and saves you the
 trouble of typing the full path.
@@ -457,19 +457,19 @@ live in Spack's directory structure.  In general, :ref:`cmd-spack-create`
 handles creating package files for you, so you can skip most of the
 details here.
 
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-``var/spack/repos/builtin/packages``
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+``var/spack/repos/spack_repo/builtin/packages``
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 A Spack installation directory is structured like a standard UNIX
 install prefix (``bin``, ``lib``, ``include``, ``var``, ``opt``,
 etc.).  Most of the code for Spack lives in ``$SPACK_ROOT/lib/spack``.
-Packages themselves live in ``$SPACK_ROOT/var/spack/repos/builtin/packages``.
+Packages themselves live in ``$SPACK_ROOT/var/spack/repos/spack_repo/builtin/packages``.
 
 If you ``cd`` to that directory, you will see directories for each
 package:
 
-.. command-output:: cd $SPACK_ROOT/var/spack/repos/builtin/packages && ls
+.. command-output:: cd $SPACK_ROOT/var/spack/repos/spack_repo/builtin/packages && ls
    :shell:
    :ellipsis: 10
 
@@ -479,7 +479,7 @@ package lives in:
 
 .. code-block:: none
 
-   $SPACK_ROOT/var/spack/repos/builtin/packages/libelf/package.py
+   $SPACK_ROOT/var/spack/repos/spack_repo/builtin/packages/libelf/package.py
 
 Alongside the ``package.py`` file, a package may contain extra
 directories or files (like patches) that it needs to build.
@@ -492,7 +492,7 @@ Packages are named after the directory containing ``package.py``. So,
 ``libelf``'s ``package.py`` lives in a directory called ``libelf``.
 The ``package.py`` file defines a class called ``Libelf``, which
 extends Spack's ``Package`` class.  For example, here is
-``$SPACK_ROOT/var/spack/repos/builtin/packages/libelf/package.py``:
+``$SPACK_ROOT/var/spack/repos/spack_repo/builtin/packages/libelf/package.py``:
 
 .. code-block:: python
    :linenos:
@@ -520,7 +520,7 @@ these:
    $ spack install libelf@0.8.13
 
 Spack sees the package name in the spec and looks for
-``libelf/package.py`` in ``var/spack/repos/builtin/packages``.
+``libelf/package.py`` in ``var/spack/repos/spack_repo/builtin/packages``.
 Likewise, if you run ``spack install py-numpy``, Spack looks for
 ``py-numpy/package.py``.
 
@@ -686,7 +686,7 @@ https://www.open-mpi.org/software/ompi/v2.1/downloads/openmpi-2.1.1.tar.bz2
 In order to handle this, you can define a ``url_for_version()`` function
 like so:
 
-.. literalinclude:: _spack_root/var/spack/repos/builtin/packages/openmpi/package.py
+.. literalinclude:: _spack_root/var/spack/repos/spack_repo/builtin/packages/openmpi/package.py
    :pyobject: Openmpi.url_for_version
 
 With the use of this ``url_for_version()``, Spack knows to download OpenMPI ``2.1.1``
@@ -787,7 +787,7 @@ of GNU. For that, Spack goes a step further and defines a mixin class that
 takes care of all of the plumbing and requires packagers to just define a proper
 ``gnu_mirror_path`` attribute:
 
-.. literalinclude:: _spack_root/var/spack/repos/builtin/packages/autoconf/package.py
+.. literalinclude:: _spack_root/var/spack/repos/spack_repo/builtin/packages/autoconf/package.py
    :lines: 9-18
 
 ^^^^^^^^^^^^^^^^^^^^^^^^
@@ -1995,7 +1995,7 @@ structure like this:
 
 .. code-block:: none
 
-   $SPACK_ROOT/var/spack/repos/builtin/packages/
+   $SPACK_ROOT/var/spack/repos/spack_repo/builtin/packages/
        mvapich2/
            package.py
            ad_lustre_rwcontig_open_source.patch
@@ -2133,7 +2133,7 @@ handles ``RPATH``:
 
 .. _pyside-patch:
 
-.. literalinclude:: _spack_root/var/spack/repos/builtin/packages/py-pyside/package.py
+.. literalinclude:: _spack_root/var/spack/repos/spack_repo/builtin/packages/py_pyside/package.py
    :pyobject: PyPyside.patch
    :linenos:
 
@@ -2201,7 +2201,7 @@ using the ``spack resource show`` command::
 
   $ spack resource show 3877ab54
   3877ab548f88597ab2327a2230ee048d2d07ace1062efe81fc92e91b7f39cd00
-      path:       /home/spackuser/src/spack/var/spack/repos/builtin/packages/m4/gnulib-pgi.patch
+      path:       /home/spackuser/src/spack/var/spack/repos/spack_repo/builtin/packages/m4/gnulib-pgi.patch
       applies to: builtin.m4
 
 ``spack resource show`` looks up downloadable resources from package
@@ -2219,7 +2219,7 @@ wonder where the extra boost patches are coming from::
           ^boost@1.68.0%apple-clang@9.0.0+atomic+chrono~clanglibcpp cxxstd=default +date_time~debug+exception+filesystem+graph~icu+iostreams+locale+log+math~mpi+multithreaded~numpy patches=2ab6c72d03dec6a4ae20220a9dfd5c8c572c5294252155b85c6874d97c323199,b37164268f34f7133cbc9a4066ae98fda08adf51e1172223f6a969909216870f ~pic+program_options~python+random+regex+serialization+shared+signals~singlethreaded+system~taggedlayout+test+thread+timer~versionedlayout+wave arch=darwin-highsierra-x86_64
   $ spack resource show b37164268
   b37164268f34f7133cbc9a4066ae98fda08adf51e1172223f6a969909216870f
-      path:       /home/spackuser/src/spack/var/spack/repos/builtin/packages/dealii/boost_1.68.0.patch
+      path:       /home/spackuser/src/spack/var/spack/repos/spack_repo/builtin/packages/dealii/boost_1.68.0.patch
       applies to: builtin.boost
       patched by: builtin.dealii
 
@@ -2930,7 +2930,7 @@ this, Spack provides four different methods that can be overridden in a package:
 
 The Qt package, for instance, uses this call:
 
-.. literalinclude:: _spack_root/var/spack/repos/builtin/packages/qt/package.py
+.. literalinclude:: _spack_root/var/spack/repos/spack_repo/builtin/packages/qt/package.py
    :pyobject: Qt.setup_dependent_build_environment
    :linenos:
 
@@ -2958,7 +2958,7 @@ variables to be used by the dependent. This is done by implementing
 :meth:`setup_dependent_package <spack.package_base.PackageBase.setup_dependent_package>`. An
 example of this can be found in the ``Python`` package:
 
-.. literalinclude:: _spack_root/var/spack/repos/builtin/packages/python/package.py
+.. literalinclude:: _spack_root/var/spack/repos/spack_repo/builtin/packages/python/package.py
    :pyobject: Python.setup_dependent_package
    :linenos:
 
@@ -3785,7 +3785,7 @@ It is usually sufficient for a packager to override a few
 build system specific helper methods or attributes to provide, for instance,
 configure arguments:
 
-.. literalinclude::  _spack_root/var/spack/repos/builtin/packages/m4/package.py
+.. literalinclude::  _spack_root/var/spack/repos/spack_repo/builtin/packages/m4/package.py
     :pyobject: M4.configure_args
     :linenos:
 
@@ -4110,7 +4110,7 @@ Shell command functions
 
 Recall the install method from ``libelf``:
 
-.. literalinclude::  _spack_root/var/spack/repos/builtin/packages/libelf/package.py
+.. literalinclude::  _spack_root/var/spack/repos/spack_repo/builtin/packages/libelf/package.py
    :pyobject: Libelf.install
    :linenos:
 
@@ -4901,7 +4901,7 @@ the one passed to install, only the MPI implementations all set some
 additional properties on it to help you out.  E.g., in openmpi, you'll
 find this:
 
-.. literalinclude:: _spack_root/var/spack/repos/builtin/packages/openmpi/package.py
+.. literalinclude:: _spack_root/var/spack/repos/spack_repo/builtin/packages/openmpi/package.py
    :pyobject: Openmpi.setup_dependent_package
 
 That code allows the ``openmpi`` package to associate an ``mpicc`` property
@@ -6001,16 +6001,16 @@ with those implemented in the package itself.
    * - Parent/Provider Package
      - Stand-alone Tests
    * - `C
-       <https://github.com/spack/spack/blob/develop/var/spack/repos/builtin/packages/c>`_
+       <https://github.com/spack/spack/blob/develop/var/spack/repos/spack_repo/builtin/packages/c>`_
      - Compiles ``hello.c`` and runs it
    * - `Cxx
-       <https://github.com/spack/spack/blob/develop/var/spack/repos/builtin/packages/cxx>`_
+       <https://github.com/spack/spack/blob/develop/var/spack/repos/spack_repo/builtin/packages/cxx>`_
      - Compiles and runs several ``hello`` programs
    * - `Fortran
-       <https://github.com/spack/spack/blob/develop/var/spack/repos/builtin/packages/fortran>`_
+       <https://github.com/spack/spack/blob/develop/var/spack/repos/spack_repo/builtin/packages/fortran>`_
      - Compiles and runs ``hello`` programs (``F`` and ``f90``)
    * - `Mpi
-       <https://github.com/spack/spack/blob/develop/var/spack/repos/builtin/packages/mpi>`_
+       <https://github.com/spack/spack/blob/develop/var/spack/repos/spack_repo/builtin/packages/mpi>`_
      - Compiles and runs ``mpi_hello`` (``c``, ``fortran``)
    * - :ref:`PythonPackage <pythonpackage>`
      - Imports modules listed in the ``self.import_modules`` property with defaults derived from the tarball
@@ -6031,7 +6031,7 @@ maintainers provide additional stand-alone tests customized to the package.
 One example of a package that adds its own stand-alone tests to those
 "inherited" by the virtual package it provides an implementation for is
 the `Openmpi package
-<https://github.com/spack/spack/blob/develop/var/spack/repos/builtin/packages/openmpi/package.py>`_.
+<https://github.com/spack/spack/blob/develop/var/spack/repos/spack_repo/builtin/packages/openmpi/package.py>`_.
 
 Below are snippets from running and viewing the stand-alone test results
 for ``openmpi``:

lib/spack/docs/repositories.rst

@@ -9,7 +9,7 @@ Package Repositories (repos.yaml)
 =================================
 
 Spack comes with thousands of built-in package recipes in
-``var/spack/repos/builtin/``.  This is a **package repository** -- a
+``var/spack/repos/spack_repo/builtin/``.  This is a **package repository** -- a
 directory that Spack searches when it needs to find a package by name.
 You may need to maintain packages for restricted, proprietary or
 experimental software separately from the built-in repository. Spack
@@ -69,7 +69,7 @@ The default ``etc/spack/defaults/repos.yaml`` file looks like this:
 .. code-block:: yaml
 
   repos:
-  - $spack/var/spack/repos/builtin
+  - $spack/var/spack/repos/spack_repo/builtin
 
 The file starts with ``repos:`` and contains a single ordered list of
 paths to repositories. Each path is on a separate line starting with
@@ -78,16 +78,16 @@ paths to repositories. Each path is on a separate line starting with
 .. code-block:: yaml
 
   repos:
-  - /opt/local-repo
-  - $spack/var/spack/repos/builtin
+  - /opt/repos/spack_repo/local_repo
+  - $spack/var/spack/repos/spack_repo/builtin
 
 When Spack interprets a spec, e.g., ``mpich`` in ``spack install mpich``,
 it searches these repositories in order (first to last) to resolve each
 package name.  In this example, Spack will look for the following
 packages and use the first valid file:
 
-1. ``/opt/local-repo/packages/mpich/package.py``
-2. ``$spack/var/spack/repos/builtin/packages/mpich/package.py``
+1. ``/opt/repos/spack_repo/local_repo/packages/mpich/package.py``
+2. ``$spack/var/spack/repos/spack_repo/builtin/packages/mpich/package.py``
 
 .. note::
 
@@ -101,14 +101,15 @@ Namespaces
 
 Every repository in Spack has an associated **namespace** defined in its
 top-level ``repo.yaml`` file.  If you look at
-``var/spack/repos/builtin/repo.yaml`` in the built-in repository, you'll
+``var/spack/repos/spack_repo/builtin/repo.yaml`` in the built-in repository, you'll
 see that its namespace is ``builtin``:
 
 .. code-block:: console
 
-  $ cat var/spack/repos/builtin/repo.yaml
+  $ cat var/spack/repos/spack_repo/builtin/repo.yaml
   repo:
     namespace: builtin
+    api: v2.0
 
 Spack records the repository namespace of each installed package.  For
 example, if you install the ``mpich`` package from the ``builtin`` repo,
@@ -217,15 +218,15 @@ Suppose you have three repositories: the builtin Spack repo
 repo containing your own prototype packages (``proto``).  Suppose they
 contain packages as follows:
 
-  +--------------+------------------------------------+-----------------------------+
-  | Namespace    | Path to repo                       | Packages                    |
-  +==============+====================================+=============================+
-  | ``proto``    | ``~/proto``                        | ``mpich``                   |
-  +--------------+------------------------------------+-----------------------------+
-  | ``llnl``     | ``/usr/local/llnl``                | ``hdf5``                    |
-  +--------------+------------------------------------+-----------------------------+
-  | ``builtin``  | ``$spack/var/spack/repos/builtin`` | ``mpich``, ``hdf5``, others |
-  +--------------+------------------------------------+-----------------------------+
+  +--------------+-----------------------------------------------+-----------------------------+
+  | Namespace    | Path to repo                                  | Packages                    |
+  +==============+===============================================+=============================+
+  | ``proto``    | ``~/my_spack_repos/spack_repo/proto``         | ``mpich``                   |
+  +--------------+-----------------------------------------------+-----------------------------+
+  | ``llnl``     | ``/usr/local/repos/spack_repo/llnl``          | ``hdf5``                    |
+  +--------------+-----------------------------------------------+-----------------------------+
+  | ``builtin``  | ``$spack/var/spack/repos/spack_repo/builtin`` | ``mpich``, ``hdf5``, others |
+  +--------------+-----------------------------------------------+-----------------------------+
 
 Suppose that ``hdf5`` depends on ``mpich``.  You can override the
 built-in ``hdf5`` by adding the ``llnl`` repo to ``repos.yaml``:
@@ -233,8 +234,8 @@ built-in ``hdf5`` by adding the ``llnl`` repo to ``repos.yaml``:
 .. code-block:: yaml
 
    repos:
-   - /usr/local/llnl
-   - $spack/var/spack/repos/builtin
+   - /usr/local/repos/spack_repo/llnl
+   - $spack/var/spack/repos/spack_repo/builtin
 
 ``spack install hdf5`` will install ``llnl.hdf5 ^builtin.mpich``.
 
@@ -243,9 +244,9 @@ If, instead, ``repos.yaml`` looks like this:
 .. code-block:: yaml
 
    repos:
-   - ~/proto
-   - /usr/local/llnl
-   - $spack/var/spack/repos/builtin
+   - ~/my_spack_repos/spack_repo/proto
+   - /usr/local/repos/spack_repo/llnl
+   - $spack/var/spack/repos/spack_repo/builtin
 
 ``spack install hdf5`` will install ``llnl.hdf5 ^proto.mpich``.
 
@@ -326,8 +327,8 @@ files, use ``spack repo list``.
 
   $ spack repo list
   ==> 2 package repositories.
-  myrepo     ~/myrepo
-  builtin    ~/spack/var/spack/repos/builtin
+  myrepo     v2.0    ~/my_spack_repos/spack_repo/myrepo
+  builtin    v2.0    ~/spack/var/spack/repos/spack_repo/builtin
 
 Each repository is listed with its associated namespace.  To get the raw,
 merged YAML from all configuration files, use ``spack config get repos``:
@@ -335,9 +336,9 @@ merged YAML from all configuration files, use ``spack config get repos``:
 .. code-block:: console
 
    $ spack config get repos
-   repos:srepos:
-   - ~/myrepo
-   - $spack/var/spack/repos/builtin
+   repos:
+   - ~/my_spack_repos/spack_repo/myrepo
+   - $spack/var/spack/repos/spack_repo/builtin
 
 Note that, unlike ``spack repo list``, this does not include the
 namespace, which is read from each repo's ``repo.yaml``.
@@ -351,66 +352,54 @@ yourself; you can use the ``spack repo create`` command.
 
 .. code-block:: console
 
-  $ spack repo create myrepo
+  $ spack repo create ~/my_spack_repos myrepo
   ==> Created repo with namespace 'myrepo'.
   ==> To register it with spack, run this command:
-    spack repo add ~/myrepo
+    spack repo add ~/my_spack_repos/spack_repo/myrepo
 
-  $ ls myrepo
+  $ ls ~/my_spack_repos/spack_repo/myrepo
   packages/  repo.yaml
 
-  $ cat myrepo/repo.yaml
+  $ cat ~/my_spack_repos/spack_repo/myrepo/repo.yaml
   repo:
     namespace: 'myrepo'
+    api: v2.0
 
-By default, the namespace of a new repo matches its directory's name.
-You can supply a custom namespace with a second argument, e.g.:
+Namespaces can also be nested, which can be useful if you have
+multiple package repositories for an organization. Spack will
+create the corresponding directory structure for you:
 
 .. code-block:: console
 
-  $ spack repo create myrepo llnl.comp
+  $ spack repo create ~/my_spack_repos llnl.comp
   ==> Created repo with namespace 'llnl.comp'.
   ==> To register it with spack, run this command:
-    spack repo add ~/myrepo
+    spack repo add ~/my_spack_repos/spack_repo/llnl/comp
 
-  $ cat myrepo/repo.yaml
+
+  $ cat ~/my_spack_repos/spack_repo/llnl/comp/repo.yaml
   repo:
     namespace: 'llnl.comp'
-
-You can also create repositories with custom structure with the ``-d/--subdirectory``
-argument, e.g.:
-
-.. code-block:: console
-
-  $ spack repo create -d applications myrepo apps
-  ==> Created repo with namespace 'apps'.
-  ==> To register it with Spack, run this command:
-    spack repo add ~/myrepo
-
-  $ ls myrepo
-  applications/  repo.yaml
-
-  $ cat myrepo/repo.yaml
-  repo:
-    namespace: apps
-    subdirectory: applications
+    api: v2.0
 
 ^^^^^^^^^^^^^^^^^^
 ``spack repo add``
 ^^^^^^^^^^^^^^^^^^
 
 Once your repository is created, you can register it with Spack with
-``spack repo add``:
+``spack repo add``. You nee to specify the path to the directory that
+contains the ``repo.yaml`` file.
 
 .. code-block:: console
 
-   $ spack repo add ./myrepo
+   $ spack repo add ~/my_spack_repos/spack_repo/llnl/comp
    ==> Added repo with namespace 'llnl.comp'.
 
    $ spack repo list
    ==> 2 package repositories.
-   llnl.comp    ~/myrepo
-   builtin      ~/spack/var/spack/repos/builtin
+  llnl.comp    v2.0    ~/my_spack_repos/spack_repo/llnl/comp
+  builtin      v2.0    ~/spack/var/spack/repos/spack_repo/builtin
+
 
 This simply adds the repo to your ``repos.yaml`` file.
 
@@ -432,46 +421,43 @@ By namespace:
 .. code-block:: console
 
   $ spack repo rm llnl.comp
-  ==> Removed repository ~/myrepo with namespace 'llnl.comp'.
+  ==> Removed repository ~/my_spack_repos/spack_repo/llnl/comp with namespace 'llnl.comp'.
 
   $ spack repo list
   ==> 1 package repository.
-  builtin    ~/spack/var/spack/repos/builtin
+  builtin    ~/spack/var/spack/repos/spack_repo/builtin
 
 By path:
 
 .. code-block:: console
 
-  $ spack repo rm ~/myrepo
-  ==> Removed repository ~/myrepo
+  $ spack repo rm ~/my_spack_repos/spack_repo/llnl/comp
+  ==> Removed repository ~/my_spack_repos/spack_repo/llnl/comp
 
   $ spack repo list
   ==> 1 package repository.
-  builtin    ~/spack/var/spack/repos/builtin
+  builtin    ~/spack/var/spack/repos/spack_repo/builtin
 
 --------------------------------
 Repo namespaces and Python
 --------------------------------
 
-You may have noticed that namespace notation for repositories is similar
-to the notation for namespaces in Python.  As it turns out, you *can*
-treat Spack repositories like Python packages; this is how they are
-implemented.
+Package repositories are implemented as Python packages. To be precise,
+they are `namespace packages
+<https://packaging.python.org/en/latest/guides/packaging-namespace-packages/>`_
+with ``spack_repo`` the top-level namespace, followed by the repository
+namespace as submodules. For example, the builtin repository corresponds
+to the Python module ``spack_repo.builtin.packages``.
 
-You could, for example, extend a ``builtin`` package in your own
+This structure allows you to extend a ``builtin`` package in your own
 repository:
 
 .. code-block:: python
 
-   from spack.pkg.builtin.mpich import Mpich
+   from spack_repo.builtin.packages.mpich.package import Mpich
 
    class MyPackage(Mpich):
        ...
 
-Spack repo namespaces are actually Python namespaces tacked on under
-``spack.pkg``.  The search semantics of ``repos.yaml`` are actually
-implemented using Python's built-in `sys.path
-<https://docs.python.org/2/library/sys.html#sys.path>`_ search.  The
-:py:mod:`spack.repo` module implements a custom `Python importer
-<https://docs.python.org/2/library/imp.html>`_.
-
+Spack populates ``sys.path`` at runtime with the path to the root of your
+package repository's ``spack_repo`` directory.

lib/spack/docs/requirements.txt

@@ -5,9 +5,9 @@ sphinx-rtd-theme==3.0.2
 python-levenshtein==0.27.1
 docutils==0.21.2
 pygments==2.19.1
-urllib3==2.3.0
+urllib3==2.4.0
 pytest==8.3.5
 isort==6.0.1
 black==25.1.0
-flake8==7.1.2
+flake8==7.2.0
 mypy==1.11.1

lib/spack/external/__init__.py

@@ -11,6 +11,7 @@
 * Homepage: https://altgraph.readthedocs.io/en/latest/index.html
 * Usage: dependency of macholib
 * Version: 0.17.3
+* License: MIT
 
 archspec
 --------
@@ -18,6 +19,7 @@
 * Homepage: https://pypi.python.org/pypi/archspec
 * Usage: Labeling, comparison and detection of microarchitectures
 * Version: 0.2.5 (commit 38ce485258ffc4fc6dd6688f8dc90cb269478c47)
+* License: Apache-2.0 or MIT
 
 astunparse
 ----------------
@@ -25,6 +27,7 @@
 * Homepage: https://github.com/simonpercivall/astunparse
 * Usage: Unparsing Python ASTs for package hashes in Spack
 * Version: 1.6.3 (plus modifications)
+* License: PSF-2.0
 * Note: This is in ``spack.util.unparse`` because it's very heavily
   modified, and we want to track coverage for it.
   Specifically, we have modified this library to generate consistent unparsed ASTs
@@ -41,6 +44,7 @@
 * Homepage: https://github.com/python-attrs/attrs
 * Usage: Needed by jsonschema.
 * Version: 22.1.0
+* License: MIT
 
 ctest_log_parser
 ----------------
@@ -48,6 +52,7 @@
 * Homepage: https://github.com/Kitware/CMake/blob/master/Source/CTest/cmCTestBuildHandler.cxx
 * Usage: Functions to parse build logs and extract error messages.
 * Version: Unversioned
+* License: BSD-3-Clause
 * Note: This is a homemade port of Kitware's CTest build handler.
 
 distro
@@ -56,6 +61,7 @@
 * Homepage: https://pypi.python.org/pypi/distro
 * Usage: Provides a more stable linux distribution detection.
 * Version: 1.8.0
+* License: Apache-2.0
 
 jinja2
 ------
@@ -63,6 +69,7 @@
 * Homepage: https://pypi.python.org/pypi/Jinja2
 * Usage: A modern and designer-friendly templating language for Python.
 * Version: 3.0.3 (last version supporting Python 3.6)
+* License: BSD-3-Clause
 
 jsonschema
 ----------
@@ -70,6 +77,7 @@
 * Homepage: https://pypi.python.org/pypi/jsonschema
 * Usage: An implementation of JSON Schema for Python.
 * Version: 3.2.0 (last version before 2.7 and 3.6 support was dropped)
+* License: MIT
 * Note: We don't include tests or benchmarks; just what Spack needs.
 
 macholib
@@ -78,6 +86,7 @@
 * Homepage: https://macholib.readthedocs.io/en/latest/index.html#
 * Usage: Manipulation of Mach-o binaries for relocating macOS buildcaches on Linux
 * Version: 1.16.2
+* License: MIT
 
 markupsafe
 ----------
@@ -85,6 +94,7 @@
 * Homepage: https://pypi.python.org/pypi/MarkupSafe
 * Usage: Implements a XML/HTML/XHTML Markup safe string for Python.
 * Version: 2.0.1 (last version supporting Python 3.6)
+* License: BSD-3-Clause
 
 pyrsistent
 ----------
@@ -92,6 +102,7 @@
 * Homepage: http://github.com/tobgu/pyrsistent/
 * Usage: Needed by `jsonschema`
 * Version: 0.18.0
+* License: MIT
 
 ruamel.yaml
 ------
@@ -101,6 +112,7 @@
   actively maintained and has more features, including round-tripping
   comments read from config files.
 * Version: 0.17.21
+* License: MIT
 
 six
 ---
@@ -108,5 +120,6 @@
 * Homepage: https://pypi.python.org/pypi/six
 * Usage: Python 2 and 3 compatibility utilities.
 * Version: 1.16.0
+* License: MIT
 
 """

lib/spack/llnl/util/filesystem.py

@@ -764,7 +764,7 @@ def copy_tree(
 
     files = glob.glob(src)
     if not files:
-        raise OSError("No such file or directory: '{0}'".format(src))
+        raise OSError("No such file or directory: '{0}'".format(src), errno.ENOENT)
 
     # For Windows hard-links and junctions, the source path must exist to make a symlink. Add
     # all symlinks to this list while traversing the tree, then when finished, make all

lib/spack/llnl/util/lang.py

@@ -15,7 +15,20 @@
 import typing
 import warnings
 from datetime import datetime, timedelta
-from typing import Callable, Dict, Iterable, List, Mapping, Optional, Tuple, TypeVar
+from typing import (
+    Any,
+    Callable,
+    Dict,
+    Generic,
+    Iterable,
+    Iterator,
+    List,
+    Mapping,
+    Optional,
+    Tuple,
+    TypeVar,
+    Union,
+)
 
 # Ignore emacs backups when listing modules
 ignore_modules = r"^\.#|~$"
@@ -424,46 +437,39 @@ def add_func_to_class(name, func):
     return cls
 
 
+K = TypeVar("K")
+V = TypeVar("V")
+
+
 @lazy_lexicographic_ordering
-class HashableMap(collections.abc.MutableMapping):
+class HashableMap(typing.MutableMapping[K, V]):
     """This is a hashable, comparable dictionary.  Hash is performed on
     a tuple of the values in the dictionary."""
 
     __slots__ = ("dict",)
 
     def __init__(self):
-        self.dict = {}
+        self.dict: Dict[K, V] = {}
 
-    def __getitem__(self, key):
+    def __getitem__(self, key: K) -> V:
         return self.dict[key]
 
-    def __setitem__(self, key, value):
+    def __setitem__(self, key: K, value: V) -> None:
         self.dict[key] = value
 
-    def __iter__(self):
+    def __iter__(self) -> Iterator[K]:
         return iter(self.dict)
 
-    def __len__(self):
+    def __len__(self) -> int:
         return len(self.dict)
 
-    def __delitem__(self, key):
+    def __delitem__(self, key: K) -> None:
         del self.dict[key]
 
     def _cmp_iter(self):
         for _, v in sorted(self.items()):
             yield v
 
-    def copy(self):
-        """Type-agnostic clone method.  Preserves subclass type."""
-        # Construct a new dict of my type
-        self_type = type(self)
-        clone = self_type()
-
-        # Copy everything from this dict into it.
-        for key in self:
-            clone[key] = self[key].copy()
-        return clone
-
 
 def match_predicate(*args):
     """Utility function for making string matching predicates.
@@ -1047,19 +1053,28 @@ def __exit__(self, exc_type, exc_value, tb):
         return True
 
 
-class classproperty:
+ClassPropertyType = TypeVar("ClassPropertyType")
+
+
+class classproperty(Generic[ClassPropertyType]):
     """Non-data descriptor to evaluate a class-level property. The function that performs
-    the evaluation is injected at creation time and take an instance (could be None) and
-    an owner (i.e. the class that originated the instance)
+    the evaluation is injected at creation time and takes an owner (i.e., the class that
+    originated the instance).
     """
 
-    def __init__(self, callback):
+    def __init__(self, callback: Callable[[Any], ClassPropertyType]) -> None:
         self.callback = callback
 
-    def __get__(self, instance, owner):
+    def __get__(self, instance, owner) -> ClassPropertyType:
         return self.callback(owner)
 
 
+#: A type alias that represents either a classproperty descriptor or a constant value of the same
+#: type. This allows derived classes to override a computed class-level property with a constant
+#: value while retaining type compatibility.
+ClassProperty = Union[ClassPropertyType, classproperty[ClassPropertyType]]
+
+
 class DeprecatedProperty:
     """Data descriptor to error or warn when a deprecated property is accessed.
 

lib/spack/spack/__init__.py

@@ -18,7 +18,7 @@
 #: version is incremented when the package API is extended in a backwards-compatible way. The major
 #: version is incremented upon breaking changes. This version is changed independently from the
 #: Spack version.
-package_api_version = (1, 0)
+package_api_version = (2, 0)
 
 #: The minimum Package API version that this version of Spack is compatible with. This should
 #: always be a tuple of the form ``(major, 0)``, since compatibility with vX.Y implies

lib/spack/spack/aliases.py

@@ -7,7 +7,7 @@
     "llvm": "clang",
     "intel-oneapi-compilers": "oneapi",
     "llvm-amdgpu": "rocmcc",
-    "intel-oneapi-compiler-classic": "intel",
+    "intel-oneapi-compilers-classic": "intel",
     "acfl": "arm",
 }
 
@@ -15,6 +15,6 @@
     "clang": "llvm",
     "oneapi": "intel-oneapi-compilers",
     "rocmcc": "llvm-amdgpu",
-    "intel": "intel-oneapi-compiler-classic",
+    "intel": "intel-oneapi-compilers-classic",
     "arm": "acfl",
 }

lib/spack/spack/bootstrap/environment.py

@@ -133,7 +133,7 @@ def mypy_root_spec() -> str:
 
 def black_root_spec() -> str:
     """Return the root spec used to bootstrap black"""
-    return _root_spec("py-black@:24.1.0")
+    return _root_spec("py-black@:25.1.0")
 
 
 def flake8_root_spec() -> str:

lib/spack/spack/build_environment.py

@@ -36,9 +36,11 @@
 import multiprocessing
 import os
 import re
+import signal
 import sys
 import traceback
 import types
+import warnings
 from collections import defaultdict
 from enum import Flag, auto
 from itertools import chain
@@ -572,12 +574,10 @@ def set_package_py_globals(pkg, context: Context = Context.BUILD):
     module.make = DeprecatedExecutable(pkg.name, "make", "gmake")
     module.gmake = DeprecatedExecutable(pkg.name, "gmake", "gmake")
     module.ninja = DeprecatedExecutable(pkg.name, "ninja", "ninja")
-    # TODO: johnwparent: add package or builder support to define these build tools
-    # for now there is no entrypoint for builders to define these on their
-    # own
+
     if sys.platform == "win32":
-        module.nmake = Executable("nmake")
-        module.msbuild = Executable("msbuild")
+        module.nmake = DeprecatedExecutable(pkg.name, "nmake", "msvc")
+        module.msbuild = DeprecatedExecutable(pkg.name, "msbuild", "msvc")
         # analog to configure for win32
         module.cscript = Executable("cscript")
 
@@ -1189,11 +1189,9 @@ def _setup_pkg_and_run(
         if isinstance(e, (spack.multimethod.NoSuchMethodError, AttributeError)):
             process = "test the installation" if context == "test" else "build from sources"
             error_msg = (
-                "The '{}' package cannot find an attribute while trying to {}. "
-                "This might be due to a change in Spack's package format "
-                "to support multiple build-systems for a single package. You can fix this "
-                "by updating the {} recipe, and you can also report the issue as a bug. "
-                "More information at https://spack.readthedocs.io/en/latest/packaging_guide.html#installation-procedure"
+                "The '{}' package cannot find an attribute while trying to {}. You can fix this "
+                "by updating the {} recipe, and you can also report the issue as a build-error or "
+                "a bug at https://github.com/spack/spack/issues"
             ).format(pkg.name, process, context)
             error_msg = colorize("@*R{{{}}}".format(error_msg))
             error_msg = "{}\n\n{}".format(str(e), error_msg)
@@ -1218,15 +1216,45 @@ def _setup_pkg_and_run(
             input_pipe.close()
 
 
-def start_build_process(pkg, function, kwargs):
+class BuildProcess:
+    def __init__(self, *, target, args) -> None:
+        self.p = multiprocessing.Process(target=target, args=args)
+
+    def start(self) -> None:
+        self.p.start()
+
+    def is_alive(self) -> bool:
+        return self.p.is_alive()
+
+    def join(self, *, timeout: Optional[int] = None):
+        self.p.join(timeout=timeout)
+
+    def terminate(self):
+        # Opportunity for graceful termination
+        self.p.terminate()
+        self.p.join(timeout=1)
+
+        # If the process didn't gracefully terminate, forcefully kill
+        if self.p.is_alive():
+            # TODO (python 3.6 removal): use self.p.kill() instead, consider removing this class
+            assert isinstance(self.p.pid, int), f"unexpected value for PID: {self.p.pid}"
+            os.kill(self.p.pid, signal.SIGKILL)
+            self.p.join()
+
+    @property
+    def exitcode(self):
+        return self.p.exitcode
+
+
+def start_build_process(pkg, function, kwargs, *, timeout: Optional[int] = None):
     """Create a child process to do part of a spack build.
 
     Args:
 
         pkg (spack.package_base.PackageBase): package whose environment we should set up the
             child process for.
-        function (typing.Callable): argless function to run in the child
-            process.
+        function (typing.Callable): argless function to run in the child process.
+        timeout: maximum time allowed to finish the execution of function
 
     Usage::
 
@@ -1254,14 +1282,14 @@ def child_fun():
         # Forward sys.stdin when appropriate, to allow toggling verbosity
         if sys.platform != "win32" and sys.stdin.isatty() and hasattr(sys.stdin, "fileno"):
             input_fd = Connection(os.dup(sys.stdin.fileno()))
-        mflags = os.environ.get("MAKEFLAGS", False)
-        if mflags:
+        mflags = os.environ.get("MAKEFLAGS")
+        if mflags is not None:
             m = re.search(r"--jobserver-[^=]*=(\d),(\d)", mflags)
             if m:
                 jobserver_fd1 = Connection(int(m.group(1)))
                 jobserver_fd2 = Connection(int(m.group(2)))
 
-        p = multiprocessing.Process(
+        p = BuildProcess(
             target=_setup_pkg_and_run,
             args=(
                 serialized_pkg,
@@ -1295,14 +1323,17 @@ def exitcode_msg(p):
         typ = "exit" if p.exitcode >= 0 else "signal"
         return f"{typ} {abs(p.exitcode)}"
 
+    p.join(timeout=timeout)
+    if p.is_alive():
+        warnings.warn(f"Terminating process, since the timeout of {timeout}s was exceeded")
+        p.terminate()
+        p.join()
+
     try:
         child_result = read_pipe.recv()
     except EOFError:
-        p.join()
         raise InstallError(f"The process has stopped unexpectedly ({exitcode_msg(p)})")
 
-    p.join()
-
     # If returns a StopPhase, raise it
     if isinstance(child_result, spack.error.StopPhase):
         # do not print

lib/spack/spack/build_systems/autotools.py

@@ -16,6 +16,7 @@
 import spack.package_base
 import spack.phase_callbacks
 import spack.spec
+import spack.util.environment
 import spack.util.prefix
 from spack.directives import build_system, conflicts, depends_on
 from spack.multimethod import when
@@ -846,7 +847,9 @@ def _remove_libtool_archives(self) -> None:
             with open(self._removed_la_files_log, mode="w", encoding="utf-8") as f:
                 f.write("\n".join(libtool_files))
 
-    def setup_build_environment(self, env):
+    def setup_build_environment(
+        self, env: spack.util.environment.EnvironmentModifications
+    ) -> None:
         if self.spec.platform == "darwin" and macos_version() >= Version("11"):
             # Many configure files rely on matching '10.*' for macOS version
             # detection and fail to add flags if it shows as version 11.

lib/spack/spack/build_systems/cached_cmake.py

@@ -2,9 +2,10 @@
 #
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
 import collections.abc
+import enum
 import os
 import re
-from typing import Tuple
+from typing import Optional, Tuple
 
 import llnl.util.filesystem as fs
 import llnl.util.tty as tty
@@ -13,6 +14,7 @@
 import spack.spec
 import spack.util.prefix
 from spack.directives import depends_on
+from spack.util.executable import which_string
 
 from .cmake import CMakeBuilder, CMakePackage
 
@@ -178,6 +180,64 @@ def initconfig_compiler_entries(self):
 
         return entries
 
+    class Scheduler(enum.Enum):
+        LSF = enum.auto()
+        SLURM = enum.auto()
+        FLUX = enum.auto()
+
+    def get_scheduler(self) -> Optional[Scheduler]:
+        spec = self.pkg.spec
+
+        # Check for Spectrum-mpi, which always uses LSF or LSF MPI variant
+        if spec.satisfies("^spectrum-mpi") or spec["mpi"].satisfies("schedulers=lsf"):
+            return self.Scheduler.LSF
+
+        # Check for Slurm MPI variants
+        slurm_checks = ["+slurm", "schedulers=slurm", "process_managers=slurm"]
+        if any(spec["mpi"].satisfies(variant) for variant in slurm_checks):
+            return self.Scheduler.SLURM
+
+        # TODO improve this when MPI implementations support flux
+        # Do this check last to avoid using a flux wrapper present next to Slurm/ LSF schedulers
+        if which_string("flux") is not None:
+            return self.Scheduler.FLUX
+
+        return None
+
+    def get_mpi_exec(self) -> Optional[str]:
+        spec = self.pkg.spec
+        scheduler = self.get_scheduler()
+
+        if scheduler == self.Scheduler.LSF:
+            return which_string("lrun")
+
+        elif scheduler == self.Scheduler.SLURM:
+            if spec["mpi"].external:
+                return which_string("srun")
+            else:
+                return os.path.join(spec["slurm"].prefix.bin, "srun")
+
+        elif scheduler == self.Scheduler.FLUX:
+            flux = which_string("flux")
+            return f"{flux};run" if flux else None
+
+        elif hasattr(spec["mpi"].package, "mpiexec"):
+            return spec["mpi"].package.mpiexec
+
+        else:
+            mpiexec = os.path.join(spec["mpi"].prefix.bin, "mpirun")
+            if not os.path.exists(mpiexec):
+                mpiexec = os.path.join(spec["mpi"].prefix.bin, "mpiexec")
+            return mpiexec
+
+    def get_mpi_exec_num_proc(self) -> str:
+        scheduler = self.get_scheduler()
+
+        if scheduler in [self.Scheduler.FLUX, self.Scheduler.LSF, self.Scheduler.SLURM]:
+            return "-n"
+        else:
+            return "-np"
+
     def initconfig_mpi_entries(self):
         spec = self.pkg.spec
 
@@ -197,27 +257,10 @@ def initconfig_mpi_entries(self):
         if hasattr(spec["mpi"], "mpifc"):
             entries.append(cmake_cache_path("MPI_Fortran_COMPILER", spec["mpi"].mpifc))
 
-        # Check for slurm
-        using_slurm = False
-        slurm_checks = ["+slurm", "schedulers=slurm", "process_managers=slurm"]
-        if any(spec["mpi"].satisfies(variant) for variant in slurm_checks):
-            using_slurm = True
-
         # Determine MPIEXEC
-        if using_slurm:
-            if spec["mpi"].external:
-                # Heuristic until we have dependents on externals
-                mpiexec = "/usr/bin/srun"
-            else:
-                mpiexec = os.path.join(spec["slurm"].prefix.bin, "srun")
-        elif hasattr(spec["mpi"].package, "mpiexec"):
-            mpiexec = spec["mpi"].package.mpiexec
-        else:
-            mpiexec = os.path.join(spec["mpi"].prefix.bin, "mpirun")
-            if not os.path.exists(mpiexec):
-                mpiexec = os.path.join(spec["mpi"].prefix.bin, "mpiexec")
+        mpiexec = self.get_mpi_exec()
 
-        if not os.path.exists(mpiexec):
+        if mpiexec is None or not os.path.exists(mpiexec.split(";")[0]):
             msg = "Unable to determine MPIEXEC, %s tests may fail" % self.pkg.name
             entries.append("# {0}\n".format(msg))
             tty.warn(msg)
@@ -230,10 +273,7 @@ def initconfig_mpi_entries(self):
                 entries.append(cmake_cache_path("MPIEXEC", mpiexec))
 
         # Determine MPIEXEC_NUMPROC_FLAG
-        if using_slurm:
-            entries.append(cmake_cache_string("MPIEXEC_NUMPROC_FLAG", "-n"))
-        else:
-            entries.append(cmake_cache_string("MPIEXEC_NUMPROC_FLAG", "-np"))
+        entries.append(cmake_cache_string("MPIEXEC_NUMPROC_FLAG", self.get_mpi_exec_num_proc()))
 
         return entries
 
@@ -276,30 +316,18 @@ def initconfig_hardware_entries(self):
             entries.append("# ROCm")
             entries.append("#------------------{0}\n".format("-" * 30))
 
-            if spec.satisfies("^blt@0.7:"):
-                rocm_root = os.path.dirname(spec["llvm-amdgpu"].prefix)
-                entries.append(cmake_cache_path("ROCM_PATH", rocm_root))
-            else:
-                # Explicitly setting HIP_ROOT_DIR may be a patch that is no longer necessary
-                entries.append(cmake_cache_path("HIP_ROOT_DIR", "{0}".format(spec["hip"].prefix)))
-                llvm_bin = spec["llvm-amdgpu"].prefix.bin
-                llvm_prefix = spec["llvm-amdgpu"].prefix
-                # Some ROCm systems seem to point to /<path>/rocm-<ver>/ and
-                # others point to /<path>/rocm-<ver>/llvm
-                if os.path.basename(os.path.normpath(llvm_prefix)) != "llvm":
-                    llvm_bin = os.path.join(llvm_prefix, "llvm/bin/")
-                entries.append(
-                    cmake_cache_filepath(
-                        "CMAKE_HIP_COMPILER", os.path.join(llvm_bin, "amdclang++")
-                    )
-                )
+            rocm_root = os.path.dirname(spec["llvm-amdgpu"].prefix)
+            entries.append(cmake_cache_path("ROCM_PATH", rocm_root))
 
             archs = self.spec.variants["amdgpu_target"].value
             if archs[0] != "none":
                 arch_str = ";".join(archs)
                 entries.append(cmake_cache_string("CMAKE_HIP_ARCHITECTURES", arch_str))
-                entries.append(cmake_cache_string("AMDGPU_TARGETS", arch_str))
-                entries.append(cmake_cache_string("GPU_TARGETS", arch_str))
+
+            llvm_bin = spec["llvm-amdgpu"].prefix.bin
+            entries.append(
+                cmake_cache_filepath("CMAKE_HIP_COMPILER", os.path.join(llvm_bin, "amdclang++"))
+            )
 
             if spec.satisfies("%gcc"):
                 entries.append(
@@ -308,6 +336,15 @@ def initconfig_hardware_entries(self):
                     )
                 )
 
+            # Extra definitions that might be required in other cases
+            if not spec.satisfies("^blt"):
+                entries.append(cmake_cache_path("HIP_ROOT_DIR", "{0}".format(spec["hip"].prefix)))
+
+                if archs[0] != "none":
+                    arch_str = ";".join(archs)
+                    entries.append(cmake_cache_string("AMDGPU_TARGETS", arch_str))
+                    entries.append(cmake_cache_string("GPU_TARGETS", arch_str))
+
         return entries
 
     def std_initconfig_entries(self):

lib/spack/spack/build_systems/cargo.py

@@ -8,6 +8,7 @@
 import spack.package_base
 import spack.phase_callbacks
 import spack.spec
+import spack.util.environment
 import spack.util.prefix
 from spack.directives import build_system, depends_on
 from spack.multimethod import when
@@ -86,7 +87,9 @@ def check_args(self):
         """Argument for ``cargo test`` during check phase"""
         return []
 
-    def setup_build_environment(self, env):
+    def setup_build_environment(
+        self, env: spack.util.environment.EnvironmentModifications
+    ) -> None:
         env.set("CARGO_HOME", self.stage.path)
 
     def build(

lib/spack/spack/build_systems/compiler.py

@@ -47,6 +47,11 @@ class CompilerPackage(spack.package_base.PackageBase):
     #: Relative path to compiler wrappers
     compiler_wrapper_link_paths: Dict[str, str] = {}
 
+    #: Optimization flags
+    opt_flags: Sequence[str] = []
+    #: Flags for generating debug information
+    debug_flags: Sequence[str] = []
+
     def __init__(self, spec: "spack.spec.Spec"):
         super().__init__(spec)
         msg = f"Supported languages for {spec} are not a subset of possible supported languages"

lib/spack/spack/build_systems/go.py

@@ -8,6 +8,7 @@
 import spack.package_base
 import spack.phase_callbacks
 import spack.spec
+import spack.util.environment
 import spack.util.prefix
 from spack.directives import build_system, depends_on
 from spack.multimethod import when
@@ -68,7 +69,9 @@ class GoBuilder(BuilderWithDefaults):
     #: Callback names for install-time test
     install_time_test_callbacks = ["check"]
 
-    def setup_build_environment(self, env):
+    def setup_build_environment(
+        self, env: spack.util.environment.EnvironmentModifications
+    ) -> None:
         env.set("GO111MODULE", "on")
         env.set("GOTOOLCHAIN", "local")
         env.set("GOPATH", fs.join_path(self.pkg.stage.path, "go"))

lib/spack/spack/build_systems/intel.py

@@ -23,6 +23,7 @@
 
 import spack.error
 import spack.phase_callbacks
+import spack.spec
 from spack.build_environment import dso_suffix
 from spack.error import InstallError
 from spack.util.environment import EnvironmentModifications
@@ -1016,7 +1017,7 @@ def libs(self):
         debug_print(result)
         return result
 
-    def setup_run_environment(self, env):
+    def setup_run_environment(self, env: EnvironmentModifications) -> None:
         """Adds environment variables to the generated module file.
 
         These environment variables come from running:
@@ -1049,11 +1050,13 @@ def setup_run_environment(self, env):
             env.set("F77", self.prefix.bin.ifort)
             env.set("F90", self.prefix.bin.ifort)
 
-    def setup_dependent_build_environment(self, env, dependent_spec):
+    def setup_dependent_build_environment(
+        self, env: EnvironmentModifications, dependent_spec: spack.spec.Spec
+    ) -> None:
         # NB: This function is overwritten by 'mpi' provider packages:
         #
-        # var/spack/repos/builtin/packages/intel-mpi/package.py
-        # var/spack/repos/builtin/packages/intel-parallel-studio/package.py
+        # var/spack/repos/spack_repo/builtin/packages/intel_mpi/package.py
+        # var/spack/repos/spack_repo/builtin/packages/intel_parallel_studio/package.py
         #
         # They call _setup_dependent_env_callback() as well, but with the
         # dictionary kwarg compilers_of_client{} present and populated.
@@ -1061,7 +1064,12 @@ def setup_dependent_build_environment(self, env, dependent_spec):
         # Handle everything in a callback version.
         self._setup_dependent_env_callback(env, dependent_spec)
 
-    def _setup_dependent_env_callback(self, env, dependent_spec, compilers_of_client={}):
+    def _setup_dependent_env_callback(
+        self,
+        env: EnvironmentModifications,
+        dependent_spec: spack.spec.Spec,
+        compilers_of_client={},
+    ) -> None:
         # Expected to be called from a client's
         # setup_dependent_build_environment(),
         # with args extended to convey the client's compilers as needed.

lib/spack/spack/build_systems/lua.py

@@ -8,6 +8,7 @@
 import spack.builder
 import spack.package_base
 import spack.spec
+import spack.util.environment
 import spack.util.executable
 import spack.util.prefix
 from spack.directives import build_system, depends_on, extends
@@ -114,5 +115,7 @@ def install(
     def _luarocks_config_path(self):
         return os.path.join(self.pkg.stage.source_path, "spack_luarocks.lua")
 
-    def setup_build_environment(self, env):
+    def setup_build_environment(
+        self, env: spack.util.environment.EnvironmentModifications
+    ) -> None:
         env.set("LUAROCKS_CONFIG", self._luarocks_config_path())

lib/spack/spack/build_systems/octave.py

@@ -4,6 +4,7 @@
 import spack.builder
 import spack.package_base
 import spack.spec
+import spack.util.environment
 import spack.util.prefix
 from spack.directives import build_system, extends
 from spack.multimethod import when
@@ -57,7 +58,9 @@ def install(
             "pkg prefix %s; pkg install %s" % (prefix, self.pkg.stage.archive_file),
         )
 
-    def setup_build_environment(self, env):
+    def setup_build_environment(
+        self, env: spack.util.environment.EnvironmentModifications
+    ) -> None:
         # octave does not like those environment variables to be set:
         env.unset("CC")
         env.unset("CXX")

lib/spack/spack/build_systems/oneapi.py

@@ -106,8 +106,8 @@ def install_component(self, installer_path):
 
             bash = Executable("bash")
 
-            # Installer writes files in ~/intel set HOME so it goes to prefix
-            bash.add_default_env("HOME", self.prefix)
+            # Installer writes files in ~/intel set HOME so it goes to staging directory
+            bash.add_default_env("HOME", join_path(self.stage.path, "home"))
             # Installer checks $XDG_RUNTIME_DIR/.bootstrapper_lock_file as well
             bash.add_default_env("XDG_RUNTIME_DIR", join_path(self.stage.path, "runtime"))
 
@@ -132,7 +132,7 @@ def install_component(self, installer_path):
         if not isdir(install_dir):
             raise RuntimeError("install failed to directory: {0}".format(install_dir))
 
-    def setup_run_environment(self, env):
+    def setup_run_environment(self, env: EnvironmentModifications) -> None:
         """Adds environment variables to the generated module file.
 
         These environment variables come from running:
@@ -311,4 +311,4 @@ def ld_flags(self):
 
 
 #: Tuple of Intel math libraries, exported to packages
-INTEL_MATH_LIBRARIES = ("intel-mkl", "intel-oneapi-mkl", "intel-parallel-studio")
+INTEL_MATH_LIBRARIES = ("intel-oneapi-mkl",)

lib/spack/spack/build_systems/python.py

@@ -13,9 +13,9 @@
 import archspec
 
 import llnl.util.filesystem as fs
-import llnl.util.lang as lang
 import llnl.util.tty as tty
 from llnl.util.filesystem import HeaderList, LibraryList, join_path
+from llnl.util.lang import ClassProperty, classproperty, match_predicate
 
 import spack.builder
 import spack.config
@@ -139,7 +139,7 @@ def view_file_conflicts(self, view, merge_map):
             ext_map = view.extensions_layout.extension_map(self.extendee_spec)
             namespaces = set(x.package.py_namespace for x in ext_map.values())
             namespace_re = r"site-packages/{0}/__init__.py".format(self.py_namespace)
-            find_namespace = lang.match_predicate(namespace_re)
+            find_namespace = match_predicate(namespace_re)
             if self.py_namespace in namespaces:
                 conflicts = list(x for x in conflicts if not find_namespace(x))
 
@@ -206,7 +206,7 @@ def remove_files_from_view(self, view, merge_map):
                 spec.package.py_namespace for name, spec in ext_map.items() if name != self.name
             )
             if self.py_namespace in remaining_namespaces:
-                namespace_init = lang.match_predicate(
+                namespace_init = match_predicate(
                     r"site-packages/{0}/__init__.py".format(self.py_namespace)
                 )
                 ignore_namespace = True
@@ -324,6 +324,27 @@ def get_external_python_for_prefix(self):
         raise StopIteration("No external python could be detected for %s to depend on" % self.spec)
 
 
+def _homepage(cls: "PythonPackage") -> Optional[str]:
+    """Get the homepage from PyPI if available."""
+    if cls.pypi:
+        name = cls.pypi.split("/")[0]
+        return f"https://pypi.org/project/{name}/"
+    return None
+
+
+def _url(cls: "PythonPackage") -> Optional[str]:
+    if cls.pypi:
+        return f"https://files.pythonhosted.org/packages/source/{cls.pypi[0]}/{cls.pypi}"
+    return None
+
+
+def _list_url(cls: "PythonPackage") -> Optional[str]:
+    if cls.pypi:
+        name = cls.pypi.split("/")[0]
+        return f"https://pypi.org/simple/{name}/"
+    return None
+
+
 class PythonPackage(PythonExtension):
     """Specialized class for packages that are built using pip."""
 
@@ -351,25 +372,9 @@ class PythonPackage(PythonExtension):
 
     py_namespace: Optional[str] = None
 
-    @lang.classproperty
-    def homepage(cls) -> Optional[str]:  # type: ignore[override]
-        if cls.pypi:
-            name = cls.pypi.split("/")[0]
-            return f"https://pypi.org/project/{name}/"
-        return None
-
-    @lang.classproperty
-    def url(cls) -> Optional[str]:
-        if cls.pypi:
-            return f"https://files.pythonhosted.org/packages/source/{cls.pypi[0]}/{cls.pypi}"
-        return None
-
-    @lang.classproperty
-    def list_url(cls) -> Optional[str]:  # type: ignore[override]
-        if cls.pypi:
-            name = cls.pypi.split("/")[0]
-            return f"https://pypi.org/simple/{name}/"
-        return None
+    homepage: ClassProperty[Optional[str]] = classproperty(_homepage)
+    url: ClassProperty[Optional[str]] = classproperty(_url)
+    list_url: ClassProperty[Optional[str]] = classproperty(_list_url)
 
     @property
     def python_spec(self) -> Spec:

lib/spack/spack/build_systems/r.py

@@ -3,8 +3,8 @@
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
 from typing import Optional, Tuple
 
-import llnl.util.lang as lang
 from llnl.util.filesystem import mkdirp
+from llnl.util.lang import ClassProperty, classproperty
 
 from spack.directives import extends
 
@@ -54,6 +54,32 @@ def install(self, pkg, spec, prefix):
         pkg.module.R(*args)
 
 
+def _homepage(cls: "RPackage") -> Optional[str]:
+    if cls.cran:
+        return f"https://cloud.r-project.org/package={cls.cran}"
+    elif cls.bioc:
+        return f"https://bioconductor.org/packages/{cls.bioc}"
+    return None
+
+
+def _url(cls: "RPackage") -> Optional[str]:
+    if cls.cran:
+        return f"https://cloud.r-project.org/src/contrib/{cls.cran}_{str(list(cls.versions)[0])}.tar.gz"
+    return None
+
+
+def _list_url(cls: "RPackage") -> Optional[str]:
+    if cls.cran:
+        return f"https://cloud.r-project.org/src/contrib/Archive/{cls.cran}/"
+    return None
+
+
+def _git(cls: "RPackage") -> Optional[str]:
+    if cls.bioc:
+        return f"https://git.bioconductor.org/packages/{cls.bioc}"
+    return None
+
+
 class RPackage(Package):
     """Specialized class for packages that are built using R.
 
@@ -77,24 +103,7 @@ class RPackage(Package):
 
     extends("r")
 
-    @lang.classproperty
-    def homepage(cls):
-        if cls.cran:
-            return f"https://cloud.r-project.org/package={cls.cran}"
-        elif cls.bioc:
-            return f"https://bioconductor.org/packages/{cls.bioc}"
-
-    @lang.classproperty
-    def url(cls):
-        if cls.cran:
-            return f"https://cloud.r-project.org/src/contrib/{cls.cran}_{str(list(cls.versions)[0])}.tar.gz"
-
-    @lang.classproperty
-    def list_url(cls):
-        if cls.cran:
-            return f"https://cloud.r-project.org/src/contrib/Archive/{cls.cran}/"
-
-    @lang.classproperty
-    def git(cls):
-        if cls.bioc:
-            return f"https://git.bioconductor.org/packages/{cls.bioc}"
+    homepage: ClassProperty[Optional[str]] = classproperty(_homepage)
+    url: ClassProperty[Optional[str]] = classproperty(_url)
+    list_url: ClassProperty[Optional[str]] = classproperty(_list_url)
+    git: ClassProperty[Optional[str]] = classproperty(_git)

lib/spack/spack/build_systems/racket.py

@@ -5,8 +5,8 @@
 from typing import Optional, Tuple
 
 import llnl.util.filesystem as fs
-import llnl.util.lang as lang
 import llnl.util.tty as tty
+from llnl.util.lang import ClassProperty, classproperty
 
 import spack.builder
 import spack.spec
@@ -19,6 +19,12 @@
 from spack.util.executable import Executable, ProcessError
 
 
+def _homepage(cls: "RacketPackage") -> Optional[str]:
+    if cls.racket_name:
+        return f"https://pkgs.racket-lang.org/package/{cls.racket_name}"
+    return None
+
+
 class RacketPackage(PackageBase):
     """Specialized class for packages that are built using Racket's
     `raco pkg install` and `raco setup` commands.
@@ -37,13 +43,7 @@ class RacketPackage(PackageBase):
     extends("racket", when="build_system=racket")
 
     racket_name: Optional[str] = None
-    parallel = True
-
-    @lang.classproperty
-    def homepage(cls):
-        if cls.racket_name:
-            return "https://pkgs.racket-lang.org/package/{0}".format(cls.racket_name)
-        return None
+    homepage: ClassProperty[Optional[str]] = classproperty(_homepage)
 
 
 @spack.builder.builder("racket")

lib/spack/spack/builder.py

@@ -59,7 +59,7 @@ def __call__(self, spec, prefix):
 def get_builder_class(pkg, name: str) -> Optional[Type["Builder"]]:
     """Return the builder class if a package module defines it."""
     cls = getattr(pkg.module, name, None)
-    if cls and cls.__module__.startswith(spack.repo.ROOT_PYTHON_NAMESPACE):
+    if cls and spack.repo.is_package_module(cls.__module__):
         return cls
     return None
 
@@ -121,6 +121,7 @@ def __init__(self, wrapped_pkg_object, root_builder):
                 new_cls_name,
                 bases,
                 {
+                    "__module__": package_cls.__module__,
                     "run_tests": property(lambda x: x.wrapped_package_object.run_tests),
                     "test_requires_compiler": property(
                         lambda x: x.wrapped_package_object.test_requires_compiler
@@ -129,7 +130,6 @@ def __init__(self, wrapped_pkg_object, root_builder):
                     "tester": property(lambda x: x.wrapped_package_object.tester),
                 },
             )
-            new_cls.__module__ = package_cls.__module__
             self.__class__ = new_cls
             self.__dict__.update(wrapped_pkg_object.__dict__)
 
@@ -185,10 +185,16 @@ def __init__(self, pkg):
         # These two methods don't follow the (self, spec, prefix) signature of phases nor
         # the (self) signature of methods, so they are added explicitly to avoid using a
         # catch-all (*args, **kwargs)
-        def setup_build_environment(self, env):
+        def setup_build_environment(
+            self, env: spack.util.environment.EnvironmentModifications
+        ) -> None:
             return self.pkg_with_dispatcher.setup_build_environment(env)
 
-        def setup_dependent_build_environment(self, env, dependent_spec):
+        def setup_dependent_build_environment(
+            self,
+            env: spack.util.environment.EnvironmentModifications,
+            dependent_spec: spack.spec.Spec,
+        ) -> None:
             return self.pkg_with_dispatcher.setup_dependent_build_environment(env, dependent_spec)
 
     return Adapter(pkg)
@@ -402,7 +408,7 @@ def fixup_install(self):
                 # do something after the package is installed
                 pass
 
-           def setup_build_environment(self, env):
+           def setup_build_environment(self, env: EnvironmentModifications) -> None:
                 env.set("MY_ENV_VAR", "my_value")
 
         class CMakeBuilder(cmake.CMakeBuilder, AnyBuilder):

lib/spack/spack/ci/__init__.py

@@ -14,7 +14,7 @@
 import tempfile
 import zipfile
 from collections import namedtuple
-from typing import Callable, Dict, List, Set, Union
+from typing import Callable, Dict, List, Optional, Set, Union
 from urllib.request import Request
 
 import llnl.path
@@ -24,6 +24,7 @@
 
 import spack
 import spack.binary_distribution as bindist
+import spack.builder
 import spack.config as cfg
 import spack.environment as ev
 import spack.error
@@ -149,10 +150,10 @@ def get_stack_changed(env_path, rev1="HEAD^", rev2="HEAD"):
     return False
 
 
-def compute_affected_packages(rev1="HEAD^", rev2="HEAD"):
+def compute_affected_packages(rev1: str = "HEAD^", rev2: str = "HEAD") -> Set[str]:
     """Determine which packages were added, removed or changed
     between rev1 and rev2, and return the names as a set"""
-    return spack.repo.get_all_package_diffs("ARC", rev1=rev1, rev2=rev2)
+    return spack.repo.get_all_package_diffs("ARC", spack.repo.builtin_repo(), rev1=rev1, rev2=rev2)
 
 
 def get_spec_filter_list(env, affected_pkgs, dependent_traverse_depth=None):
@@ -613,32 +614,40 @@ def copy_stage_logs_to_artifacts(job_spec: spack.spec.Spec, job_log_dir: str) ->
     job_spec, and attempts to copy the files into the directory given
     by job_log_dir.
 
-    Args:
+    Parameters:
         job_spec: spec associated with spack install log
         job_log_dir: path into which build log should be copied
     """
     tty.debug(f"job spec: {job_spec}")
-
-    try:
-        package_metadata_root = pathlib.Path(spack.store.STORE.layout.metadata_path(job_spec))
-    except spack.error.SpackError as e:
-        tty.error(f"Cannot copy logs: {str(e)}")
+    if not job_spec.concrete:
+        tty.warn("Cannot copy artifacts for non-concrete specs")
         return
 
-    # Get the package's archived files
-    archive_files = []
-    archive_root = package_metadata_root / "archived-files"
-    if archive_root.is_dir():
-        archive_files = [f for f in archive_root.rglob("*") if f.is_file()]
-    else:
-        msg = "Cannot copy package archived files: archived-files must be a directory"
-        tty.warn(msg)
+    package_metadata_root = pathlib.Path(spack.store.STORE.layout.metadata_path(job_spec))
+    if not os.path.isdir(package_metadata_root):
+        # Fallback to using the stage directory
+        job_pkg = job_spec.package
 
+        package_metadata_root = pathlib.Path(job_pkg.stage.path)
+        archive_files = spack.builder.create(job_pkg).archive_files
+        tty.warn("Package not installed, falling back to use stage dir")
+        tty.debug(f"stage dir: {package_metadata_root}")
+    else:
+        # Get the package's archived files
+        archive_files = []
+        archive_root = package_metadata_root / "archived-files"
+        if os.path.isdir(archive_root):
+            archive_files = [str(f) for f in archive_root.rglob("*") if os.path.isfile(f)]
+        else:
+            tty.debug(f"No archived files detected at {archive_root}")
+
+    # Try zipped and unzipped versions of the build log
     build_log_zipped = package_metadata_root / "spack-build-out.txt.gz"
+    build_log = package_metadata_root / "spack-build-out.txt"
     build_env_mods = package_metadata_root / "spack-build-env.txt"
 
-    for f in [build_log_zipped, build_env_mods, *archive_files]:
-        copy_files_to_artifacts(str(f), job_log_dir)
+    for f in [build_log_zipped, build_log, build_env_mods, *archive_files]:
+        copy_files_to_artifacts(str(f), job_log_dir, compress_artifacts=True)
 
 
 def copy_test_logs_to_artifacts(test_stage, job_test_dir):
@@ -651,11 +660,12 @@ def copy_test_logs_to_artifacts(test_stage, job_test_dir):
     """
     tty.debug(f"test stage: {test_stage}")
     if not os.path.exists(test_stage):
-        msg = f"Cannot copy test logs: job test stage ({test_stage}) does not exist"
-        tty.error(msg)
+        tty.error(f"Cannot copy test logs: job test stage ({test_stage}) does not exist")
         return
 
-    copy_files_to_artifacts(os.path.join(test_stage, "*", "*.txt"), job_test_dir)
+    copy_files_to_artifacts(
+        os.path.join(test_stage, "*", "*.txt"), job_test_dir, compress_artifacts=True
+    )
 
 
 def download_and_extract_artifacts(url, work_dir) -> str:
@@ -1294,35 +1304,34 @@ def display_broken_spec_messages(base_url, hashes):
         tty.msg(msg)
 
 
-def run_standalone_tests(**kwargs):
+def run_standalone_tests(
+    *,
+    cdash: Optional[CDashHandler] = None,
+    fail_fast: bool = False,
+    log_file: Optional[str] = None,
+    job_spec: Optional[spack.spec.Spec] = None,
+    repro_dir: Optional[str] = None,
+    timeout: Optional[int] = None,
+):
     """Run stand-alone tests on the current spec.
 
-    Arguments:
-       kwargs (dict): dictionary of arguments used to run the tests
-
-    List of recognized keys:
-
-    * "cdash" (CDashHandler): (optional) cdash handler instance
-    * "fail_fast" (bool): (optional) terminate tests after the first failure
-    * "log_file" (str): (optional) test log file name if NOT CDash reporting
-    * "job_spec" (Spec): spec that was built
-    * "repro_dir" (str): reproduction directory
+    Args:
+        cdash: cdash handler instance
+        fail_fast: terminate tests after the first failure
+        log_file: test log file name if NOT CDash reporting
+        job_spec: spec that was built
+        repro_dir: reproduction directory
+        timeout: maximum time (in seconds) that tests are allowed to run
     """
-    cdash = kwargs.get("cdash")
-    fail_fast = kwargs.get("fail_fast")
-    log_file = kwargs.get("log_file")
-
     if cdash and log_file:
         tty.msg(f"The test log file {log_file} option is ignored with CDash reporting")
         log_file = None
 
     # Error out but do NOT terminate if there are missing required arguments.
-    job_spec = kwargs.get("job_spec")
     if not job_spec:
         tty.error("Job spec is required to run stand-alone tests")
         return
 
-    repro_dir = kwargs.get("repro_dir")
     if not repro_dir:
         tty.error("Reproduction directory is required for stand-alone tests")
         return
@@ -1331,6 +1340,9 @@ def run_standalone_tests(**kwargs):
     if fail_fast:
         test_args.append("--fail-fast")
 
+    if timeout is not None:
+        test_args.extend(["--timeout", str(timeout)])
+
     if cdash:
         test_args.extend(cdash.args())
     else:

lib/spack/spack/ci/common.py

@@ -2,9 +2,13 @@
 #
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
 import copy
+import errno
+import glob
+import gzip
 import json
 import os
 import re
+import shutil
 import sys
 import time
 from collections import deque
@@ -25,6 +29,7 @@
 import spack.mirrors.mirror
 import spack.schema
 import spack.spec
+import spack.util.compression as compression
 import spack.util.spack_yaml as syaml
 import spack.util.url as url_util
 import spack.util.web as web_util
@@ -40,22 +45,67 @@
 _urlopen = web_util.urlopen
 
 
-def copy_files_to_artifacts(src, artifacts_dir):
+def copy_gzipped(glob_or_path: str, dest: str) -> None:
+    """Copy all of the files in the source glob/path to the destination.
+
+    Args:
+        glob_or_path: path to file to test
+        dest: destination path to copy to
+    """
+
+    files = glob.glob(glob_or_path)
+    if not files:
+        raise OSError("No such file or directory: '{0}'".format(glob_or_path), errno.ENOENT)
+    if len(files) > 1 and not os.path.isdir(dest):
+        raise ValueError(
+            "'{0}' matches multiple files but '{1}' is not a directory".format(glob_or_path, dest)
+        )
+
+    def is_gzipped(path):
+        with open(path, "rb") as fd:
+            return compression.GZipFileType().matches_magic(fd)
+
+    for src in files:
+        if is_gzipped(src):
+            fs.copy(src, dest)
+        else:
+            # Compress and copy in one step
+            src_name = os.path.basename(src)
+            if os.path.isdir(dest):
+                zipped = os.path.join(dest, f"{src_name}.gz")
+            elif not dest.endswith(".gz"):
+                zipped = f"{dest}.gz"
+            else:
+                zipped = dest
+
+            with open(src, "rb") as fin, gzip.open(zipped, "wb") as fout:
+                shutil.copyfileobj(fin, fout)
+
+
+def copy_files_to_artifacts(
+    src: str, artifacts_dir: str, *, compress_artifacts: bool = False
+) -> None:
     """
     Copy file(s) to the given artifacts directory
 
-    Parameters:
+    Args:
         src (str): the glob-friendly path expression for the file(s) to copy
         artifacts_dir (str): the destination directory
+        compress_artifacts (bool): option to compress copied artifacts using Gzip
     """
     try:
-        fs.copy(src, artifacts_dir)
+
+        if compress_artifacts:
+            copy_gzipped(src, artifacts_dir)
+        else:
+            fs.copy(src, artifacts_dir)
     except Exception as err:
-        msg = (
-            f"Unable to copy files ({src}) to artifacts {artifacts_dir} due to "
-            f"exception: {str(err)}"
+        tty.warn(
+            (
+                f"Unable to copy files ({src}) to artifacts {artifacts_dir} due to "
+                f"exception: {str(err)}"
+            )
         )
-        tty.warn(msg)
 
 
 def win_quote(quote_str: str) -> str:

lib/spack/spack/cmd/__init__.py

@@ -436,7 +436,7 @@ def display_specs(specs, args=None, **kwargs):
         all_headers (bool): show headers even when arch/compiler aren't defined
         status_fn (typing.Callable): if provided, prepend install-status info
         output (typing.IO): A file object to write to. Default is ``sys.stdout``
-
+        specfile_format (bool): specfile format of the current spec
     """
 
     def get_arg(name, default=None):
@@ -458,6 +458,7 @@ def get_arg(name, default=None):
     all_headers = get_arg("all_headers", False)
     output = get_arg("output", sys.stdout)
     status_fn = get_arg("status_fn", None)
+    specfile_format = get_arg("specfile_format", False)
 
     decorator = get_arg("decorator", None)
     if decorator is None:
@@ -479,6 +480,9 @@ def get_arg(name, default=None):
         vfmt = "{variants}" if variants else ""
         format_string = nfmt + "{@version}" + vfmt + ffmt
 
+    if specfile_format:
+        format_string = "[{specfile_version}] " + format_string
+
     def fmt(s, depth=0):
         """Formatter function for all output specs"""
         string = ""

lib/spack/spack/cmd/buildcache.py

@@ -76,9 +76,6 @@ def setup_parser(subparser: argparse.ArgumentParser):
         default=False,
         help="regenerate buildcache index after building package(s)",
     )
-    push.add_argument(
-        "--spec-file", default=None, help="create buildcache entry for spec from json or yaml file"
-    )
     push.add_argument(
         "--only",
         default="package,dependencies",
@@ -192,28 +189,14 @@ def setup_parser(subparser: argparse.ArgumentParser):
         default=lambda: spack.config.default_modify_scope(),
         help="configuration scope containing mirrors to check",
     )
-    # Unfortunately there are 3 ways to do the same thing here:
-    check_specs = check.add_mutually_exclusive_group()
-    check_specs.add_argument(
-        "-s", "--spec", help="check single spec instead of release specs file"
-    )
-    check_specs.add_argument(
-        "--spec-file",
-        help="check single spec from json or yaml file instead of release specs file",
-    )
+
     arguments.add_common_arguments(check, ["specs"])
 
     check.set_defaults(func=check_fn)
 
     # Download tarball and specfile
     download = subparsers.add_parser("download", help=download_fn.__doc__)
-    download_spec_or_specfile = download.add_mutually_exclusive_group(required=True)
-    download_spec_or_specfile.add_argument(
-        "-s", "--spec", help="download built tarball for spec from mirror"
-    )
-    download_spec_or_specfile.add_argument(
-        "--spec-file", help="download built tarball for spec (from json or yaml file) from mirror"
-    )
+    download.add_argument("-s", "--spec", help="download built tarball for spec from mirror")
     download.add_argument(
         "-p",
         "--path",
@@ -223,28 +206,10 @@ def setup_parser(subparser: argparse.ArgumentParser):
     )
     download.set_defaults(func=download_fn)
 
-    # Get buildcache name
-    getbuildcachename = subparsers.add_parser(
-        "get-buildcache-name", help=get_buildcache_name_fn.__doc__
-    )
-    getbuildcachename_spec_or_specfile = getbuildcachename.add_mutually_exclusive_group(
-        required=True
-    )
-    getbuildcachename_spec_or_specfile.add_argument(
-        "-s", "--spec", help="spec string for which buildcache name is desired"
-    )
-    getbuildcachename_spec_or_specfile.add_argument(
-        "--spec-file", help="path to spec json or yaml file for which buildcache name is desired"
-    )
-    getbuildcachename.set_defaults(func=get_buildcache_name_fn)
-
     # Given the root spec, save the yaml of the dependent spec to a file
     savespecfile = subparsers.add_parser("save-specfile", help=save_specfile_fn.__doc__)
     savespecfile_spec_or_specfile = savespecfile.add_mutually_exclusive_group(required=True)
     savespecfile_spec_or_specfile.add_argument("--root-spec", help="root spec of dependent spec")
-    savespecfile_spec_or_specfile.add_argument(
-        "--root-specfile", help="path to json or yaml file containing root spec of dependent spec"
-    )
     savespecfile.add_argument(
         "-s",
         "--specs",
@@ -380,14 +345,8 @@ def _specs_to_be_packaged(
 
 def push_fn(args):
     """create a binary package and push it to a mirror"""
-    if args.spec_file:
-        tty.warn(
-            "The flag `--spec-file` is deprecated and will be removed in Spack 0.22. "
-            "Use positional arguments instead."
-        )
-
-    if args.specs or args.spec_file:
-        roots = _matching_specs(spack.cmd.parse_specs(args.specs or args.spec_file))
+    if args.specs:
+        roots = _matching_specs(spack.cmd.parse_specs(args.specs))
     else:
         roots = spack.cmd.require_active_env(cmd_name="buildcache push").concrete_roots()
 
@@ -529,22 +488,7 @@ def check_fn(args: argparse.Namespace):
     this command uses the process exit code to indicate its result, specifically, if the
     exit code is non-zero, then at least one of the indicated specs needs to be rebuilt
     """
-    if args.spec_file:
-        specs_arg = (
-            args.spec_file if os.path.sep in args.spec_file else os.path.join(".", args.spec_file)
-        )
-        tty.warn(
-            "The flag `--spec-file` is deprecated and will be removed in Spack 0.22. "
-            f"Use `spack buildcache check {specs_arg}` instead."
-        )
-    elif args.spec:
-        specs_arg = args.spec
-        tty.warn(
-            "The flag `--spec` is deprecated and will be removed in Spack 0.23. "
-            f"Use `spack buildcache check {specs_arg}` instead."
-        )
-    else:
-        specs_arg = args.specs
+    specs_arg = args.specs
 
     if specs_arg:
         specs = _matching_specs(spack.cmd.parse_specs(specs_arg))
@@ -578,13 +522,7 @@ def download_fn(args):
     code indicates that the command failed to download at least one of the required buildcache
     components
     """
-    if args.spec_file:
-        tty.warn(
-            "The flag `--spec-file` is deprecated and will be removed in Spack 0.22. "
-            "Use --spec instead."
-        )
-
-    specs = _matching_specs(spack.cmd.parse_specs(args.spec or args.spec_file))
+    specs = _matching_specs(spack.cmd.parse_specs(args.spec))
 
     if len(specs) != 1:
         tty.die("a single spec argument is required to download from a buildcache")
@@ -593,15 +531,6 @@ def download_fn(args):
         sys.exit(1)
 
 
-def get_buildcache_name_fn(args):
-    """get name (prefix) of buildcache entries for this spec"""
-    tty.warn("This command is deprecated and will be removed in Spack 0.22.")
-    specs = _matching_specs(spack.cmd.parse_specs(args.spec or args.spec_file))
-    if len(specs) != 1:
-        tty.die("a single spec argument is required to get buildcache name")
-    print(bindist.tarball_name(specs[0], ""))
-
-
 def save_specfile_fn(args):
     """get full spec for dependencies and write them to files in the specified output directory
 
@@ -609,13 +538,7 @@ def save_specfile_fn(args):
     successful. if any errors or exceptions are encountered, or if expected command-line arguments
     are not provided, then the exit code will be non-zero
     """
-    if args.root_specfile:
-        tty.warn(
-            "The flag `--root-specfile` is deprecated and will be removed in Spack 0.22. "
-            "Use --root-spec instead."
-        )
-
-    specs = spack.cmd.parse_specs(args.root_spec or args.root_specfile)
+    specs = spack.cmd.parse_specs(args.root_spec)
 
     if len(specs) != 1:
         tty.die("a single spec argument is required to save specfile")

lib/spack/spack/cmd/ci.py

@@ -4,7 +4,6 @@
 
 import json
 import os
-import re
 import shutil
 import sys
 from typing import Dict
@@ -26,12 +25,10 @@
 import spack.hash_types as ht
 import spack.mirrors.mirror
 import spack.package_base
-import spack.paths
 import spack.repo
 import spack.spec
 import spack.stage
 import spack.util.executable
-import spack.util.git
 import spack.util.gpg as gpg_util
 import spack.util.timer as timer
 import spack.util.url as url_util
@@ -45,7 +42,6 @@
 SPACK_COMMAND = "spack"
 INSTALL_FAIL_CODE = 1
 FAILED_CREATE_BUILDCACHE_CODE = 100
-BUILTIN = re.compile(r"var\/spack\/repos\/builtin\/packages\/([^\/]+)\/package\.py")
 
 
 def deindent(desc):
@@ -164,6 +160,12 @@ def setup_parser(subparser):
         default=False,
         help="stop stand-alone tests after the first failure",
     )
+    rebuild.add_argument(
+        "--timeout",
+        type=int,
+        default=None,
+        help="maximum time (in seconds) that tests are allowed to run",
+    )
     rebuild.set_defaults(func=ci_rebuild)
     spack.cmd.common.arguments.add_common_arguments(rebuild, ["jobs"])
 
@@ -451,7 +453,7 @@ def ci_rebuild(args):
 
     # Arguments when installing the root from sources
     deps_install_args = install_args + ["--only=dependencies"]
-    root_install_args = install_args + ["--only=package"]
+    root_install_args = install_args + ["--keep-stage", "--only=package"]
 
     if cdash_handler:
         # Add additional arguments to `spack install` for CDash reporting.
@@ -491,6 +493,9 @@ def ci_rebuild(args):
     # Copy logs and archived files from the install metadata (.spack) directory to artifacts now
     spack_ci.copy_stage_logs_to_artifacts(job_spec, job_log_dir)
 
+    # Clear the stage directory
+    spack.stage.purge()
+
     # If the installation succeeded and we're running stand-alone tests for
     # the package, run them and copy the output. Failures of any kind should
     # *not* terminate the build process or preclude creating the build cache.
@@ -525,6 +530,7 @@ def ci_rebuild(args):
                     fail_fast=args.fail_fast,
                     log_file=log_file,
                     repro_dir=repro_dir,
+                    timeout=args.timeout,
                 )
 
             except Exception as err:
@@ -783,18 +789,17 @@ def ci_verify_versions(args):
     then parses the git diff between the two to determine which packages
     have been modified verifies the new checksums inside of them.
     """
-    with fs.working_dir(spack.paths.prefix):
-        # We use HEAD^1 explicitly on the merge commit created by
-        # GitHub Actions. However HEAD~1 is a safer default for the helper function.
-        files = spack.util.git.get_modified_files(from_ref=args.from_ref, to_ref=args.to_ref)
-
-    # Get a list of package names from the modified files.
-    pkgs = [(m.group(1), p) for p in files for m in [BUILTIN.search(p)] if m]
+    # Get a list of all packages that have been changed or added
+    # between from_ref and to_ref
+    pkgs = spack.repo.get_all_package_diffs(
+        "AC", spack.repo.builtin_repo(), args.from_ref, args.to_ref
+    )
 
     failed_version = False
-    for pkg_name, path in pkgs:
+    for pkg_name in pkgs:
         spec = spack.spec.Spec(pkg_name)
         pkg = spack.repo.PATH.get_pkg_class(spec.name)(spec)
+        path = spack.repo.PATH.package_path(pkg_name)
 
         # Skip checking manual download packages and trust the maintainers
         if pkg.manual_download:
@@ -818,7 +823,7 @@ def ci_verify_versions(args):
             # TODO: enforce every version have a commit or a sha256 defined if not
             # an infinite version (there are a lot of package's where this doesn't work yet.)
 
-        with fs.working_dir(spack.paths.prefix):
+        with fs.working_dir(os.path.dirname(path)):
             added_checksums = spack_ci.get_added_versions(
                 checksums_version_dict, path, from_ref=args.from_ref, to_ref=args.to_ref
             )

lib/spack/spack/cmd/compiler.py

@@ -63,7 +63,7 @@ def setup_parser(subparser):
     )
 
     # List
-    list_parser = sp.add_parser("list", help="list available compilers")
+    list_parser = sp.add_parser("list", aliases=["ls"], help="list available compilers")
     list_parser.add_argument(
         "--scope", action=arguments.ConfigScope, help="configuration scope to read from"
     )
@@ -216,5 +216,6 @@ def compiler(parser, args):
         "rm": compiler_remove,
         "info": compiler_info,
         "list": compiler_list,
+        "ls": compiler_list,
     }
     action[args.compiler_command](args)

lib/spack/spack/cmd/create.py

@@ -23,7 +23,7 @@
 from spack.util.editor import editor
 from spack.util.executable import which
 from spack.util.format import get_version_lines
-from spack.util.naming import mod_to_class, simplify_name, valid_fully_qualified_module_name
+from spack.util.naming import pkg_name_to_class_name, simplify_name
 
 description = "create a new package file"
 section = "packaging"
@@ -95,7 +95,7 @@ class BundlePackageTemplate:
 
     def __init__(self, name: str, versions, languages: List[str]):
         self.name = name
-        self.class_name = mod_to_class(name)
+        self.class_name = pkg_name_to_class_name(name)
         self.versions = versions
         self.languages = languages
 
@@ -572,7 +572,7 @@ def edit(self, spec, prefix):
 class IntelPackageTemplate(PackageTemplate):
     """Provides appropriate overrides for licensed Intel software"""
 
-    base_class_name = "IntelPackage"
+    base_class_name = "IntelOneApiPackage"
 
     body_def = """\
     # FIXME: Override `setup_environment` if necessary."""
@@ -874,7 +874,7 @@ def get_name(name, url):
 
     result = simplify_name(result)
 
-    if not valid_fully_qualified_module_name(result):
+    if not re.match(r"^[a-z0-9-]+$", result):
         tty.die("Package name can only contain a-z, 0-9, and '-'")
 
     return result

lib/spack/spack/cmd/develop.py

@@ -102,7 +102,7 @@ def assure_concrete_spec(env: spack.environment.Environment, spec: spack.spec.Sp
                     )
         else:
             # look up the maximum version so infintiy versions are preferred for develop
-            version = max(spec.package_class.versions.keys())
+            version = max(spack.repo.PATH.get_pkg_class(spec.fullname).versions.keys())
             tty.msg(f"Defaulting to highest version: {spec.name}@{version}")
     spec.versions = spack.version.VersionList([version])
 

lib/spack/spack/cmd/external.py

@@ -62,7 +62,7 @@ def setup_parser(subparser):
         "package Spack knows how to find."
     )
 
-    sp.add_parser("list", help="list detectable packages, by repository and name")
+    sp.add_parser("list", aliases=["ls"], help="list detectable packages, by repository and name")
 
     read_cray_manifest = sp.add_parser(
         "read-cray-manifest",
@@ -259,6 +259,7 @@ def external(parser, args):
     action = {
         "find": external_find,
         "list": external_list,
+        "ls": external_list,
         "read-cray-manifest": external_read_cray_manifest,
     }
     action[args.external_command](args)

lib/spack/spack/cmd/find.py

@@ -51,6 +51,12 @@ def setup_parser(subparser):
         "-I", "--install-status", action="store_true", help="show install status of packages"
     )
 
+    subparser.add_argument(
+        "--specfile-format",
+        action="store_true",
+        help="show the specfile format for installed deps ",
+    )
+
     subparser.add_argument(
         "-d", "--deps", action="store_true", help="output dependencies along with found specs"
     )
@@ -280,6 +286,7 @@ def root_decorator(spec, string):
             show_flags=True,
             decorator=root_decorator,
             variants=True,
+            specfile_format=args.specfile_format,
         )
 
     print()
@@ -301,6 +308,7 @@ def root_decorator(spec, string):
             namespace=True,
             show_flags=True,
             variants=True,
+            specfile_format=args.specfile_format,
         )
         print()
 
@@ -390,7 +398,12 @@ def find(parser, args):
             if args.show_concretized:
                 display_results += concretized_but_not_installed
             cmd.display_specs(
-                display_results, args, decorator=decorator, all_headers=True, status_fn=status_fn
+                display_results,
+                args,
+                decorator=decorator,
+                all_headers=True,
+                status_fn=status_fn,
+                specfile_format=args.specfile_format,
             )
 
         # print number of installed packages last (as the list may be long)

lib/spack/spack/cmd/list.py

@@ -10,11 +10,13 @@
 import re
 import sys
 from html import escape
+from typing import Type
 
 import llnl.util.tty as tty
 from llnl.util.tty.colify import colify
 
 import spack.deptypes as dt
+import spack.package_base
 import spack.repo
 from spack.cmd.common import arguments
 from spack.version import VersionList
@@ -139,10 +141,10 @@ def name_only(pkgs, out):
         tty.msg("%d packages" % len(pkgs))
 
 
-def github_url(pkg):
+def github_url(pkg: Type[spack.package_base.PackageBase]) -> str:
     """Link to a package file on github."""
-    url = "https://github.com/spack/spack/blob/develop/var/spack/repos/builtin/packages/{0}/package.py"
-    return url.format(pkg.name)
+    mod_path = pkg.__module__.replace(".", "/")
+    return f"https://github.com/spack/spack/blob/develop/var/spack/{mod_path}.py"
 
 
 def rows_for_ncols(elts, ncols):

lib/spack/spack/cmd/pkg.py

@@ -89,17 +89,17 @@ def setup_parser(subparser):
 
 def pkg_add(args):
     """add a package to the git stage with `git add`"""
-    spack.repo.add_package_to_git_stage(args.packages)
+    spack.repo.add_package_to_git_stage(args.packages, spack.repo.builtin_repo())
 
 
 def pkg_list(args):
     """list packages associated with a particular spack git revision"""
-    colify(spack.repo.list_packages(args.rev))
+    colify(spack.repo.list_packages(args.rev, spack.repo.builtin_repo()))
 
 
 def pkg_diff(args):
     """compare packages available in two different git revisions"""
-    u1, u2 = spack.repo.diff_packages(args.rev1, args.rev2)
+    u1, u2 = spack.repo.diff_packages(args.rev1, args.rev2, spack.repo.builtin_repo())
 
     if u1:
         print("%s:" % args.rev1)
@@ -114,21 +114,23 @@ def pkg_diff(args):
 
 def pkg_removed(args):
     """show packages removed since a commit"""
-    u1, u2 = spack.repo.diff_packages(args.rev1, args.rev2)
+    u1, u2 = spack.repo.diff_packages(args.rev1, args.rev2, spack.repo.builtin_repo())
     if u1:
         colify(sorted(u1))
 
 
 def pkg_added(args):
     """show packages added since a commit"""
-    u1, u2 = spack.repo.diff_packages(args.rev1, args.rev2)
+    u1, u2 = spack.repo.diff_packages(args.rev1, args.rev2, spack.repo.builtin_repo())
     if u2:
         colify(sorted(u2))
 
 
 def pkg_changed(args):
     """show packages changed since a commit"""
-    packages = spack.repo.get_all_package_diffs(args.type, args.rev1, args.rev2)
+    packages = spack.repo.get_all_package_diffs(
+        args.type, spack.repo.builtin_repo(), args.rev1, args.rev2
+    )
 
     if packages:
         colify(sorted(packages))

lib/spack/spack/cmd/repo.py

@@ -4,6 +4,7 @@
 
 import os
 import sys
+from typing import List
 
 import llnl.util.tty as tty
 
@@ -24,9 +25,7 @@ def setup_parser(subparser):
     create_parser = sp.add_parser("create", help=repo_create.__doc__)
     create_parser.add_argument("directory", help="directory to create the repo in")
     create_parser.add_argument(
-        "namespace",
-        help="namespace to identify packages in the repository (defaults to the directory name)",
-        nargs="?",
+        "namespace", help="name or namespace to identify packages in the repository"
     )
     create_parser.add_argument(
         "-d",
@@ -138,7 +137,7 @@ def repo_remove(args):
 def repo_list(args):
     """show registered repositories and their namespaces"""
     roots = spack.config.get("repos", scope=args.scope)
-    repos = []
+    repos: List[spack.repo.Repo] = []
     for r in roots:
         try:
             repos.append(spack.repo.from_path(r))
@@ -146,17 +145,14 @@ def repo_list(args):
             continue
 
     if sys.stdout.isatty():
-        msg = "%d package repositor" % len(repos)
-        msg += "y." if len(repos) == 1 else "ies."
-        tty.msg(msg)
+        tty.msg(f"{len(repos)} package repositor" + ("y." if len(repos) == 1 else "ies."))
 
     if not repos:
         return
 
     max_ns_len = max(len(r.namespace) for r in repos)
     for repo in repos:
-        fmt = "%%-%ds%%s" % (max_ns_len + 4)
-        print(fmt % (repo.namespace, repo.root))
+        print(f"{repo.namespace:<{max_ns_len + 4}}{repo.package_api_str:<8}{repo.root}")
 
 
 def repo(parser, args):

lib/spack/spack/cmd/solve.py

@@ -136,20 +136,7 @@ def solve(parser, args):
     setup_only = set(show) == {"asp"}
     unify = spack.config.get("concretizer:unify")
     allow_deprecated = spack.config.get("config:deprecated", False)
-    if unify != "when_possible":
-        # set up solver parameters
-        # Note: reuse and other concretizer prefs are passed as configuration
-        result = solver.solve(
-            specs,
-            out=output,
-            timers=args.timers,
-            stats=args.stats,
-            setup_only=setup_only,
-            allow_deprecated=allow_deprecated,
-        )
-        if not setup_only:
-            _process_result(result, show, required_format, kwargs)
-    else:
+    if unify == "when_possible":
         for idx, result in enumerate(
             solver.solve_in_rounds(
                 specs,
@@ -166,3 +153,29 @@ def solve(parser, args):
                 print("% END ROUND {0}\n".format(idx))
             if not setup_only:
                 _process_result(result, show, required_format, kwargs)
+    elif unify:
+        # set up solver parameters
+        # Note: reuse and other concretizer prefs are passed as configuration
+        result = solver.solve(
+            specs,
+            out=output,
+            timers=args.timers,
+            stats=args.stats,
+            setup_only=setup_only,
+            allow_deprecated=allow_deprecated,
+        )
+        if not setup_only:
+            _process_result(result, show, required_format, kwargs)
+    else:
+        for spec in specs:
+            tty.msg("SOLVING SPEC:", spec)
+            result = solver.solve(
+                [spec],
+                out=output,
+                timers=args.timers,
+                stats=args.stats,
+                setup_only=setup_only,
+                allow_deprecated=allow_deprecated,
+            )
+            if not setup_only:
+                _process_result(result, show, required_format, kwargs)

lib/spack/spack/cmd/style.py

@@ -59,7 +59,7 @@ def is_package(f):
     packages, since we allow `from spack import *` and poking globals
     into packages.
     """
-    return f.startswith("var/spack/repos/") and f.endswith("package.py")
+    return f.startswith("var/spack/") and f.endswith("package.py")
 
 
 #: decorator for adding tools to the list
@@ -380,7 +380,7 @@ def run_black(black_cmd, file_list, args):
 def _module_part(root: str, expr: str):
     parts = expr.split(".")
     # spack.pkg is for repositories, don't try to resolve it here.
-    if ".".join(parts[:2]) == spack.repo.ROOT_PYTHON_NAMESPACE:
+    if expr.startswith(spack.repo.PKG_MODULE_PREFIX_V1) or expr == "spack.pkg":
         return None
     while parts:
         f1 = os.path.join(root, "lib", "spack", *parts) + ".py"

lib/spack/spack/cmd/test.py

@@ -65,6 +65,12 @@ def setup_parser(subparser):
     run_parser.add_argument(
         "--help-cdash", action="store_true", help="show usage instructions for CDash reporting"
     )
+    run_parser.add_argument(
+        "--timeout",
+        type=int,
+        default=None,
+        help="maximum time (in seconds) that tests are allowed to run",
+    )
 
     cd_group = run_parser.add_mutually_exclusive_group()
     arguments.add_common_arguments(cd_group, ["clean", "dirty"])
@@ -176,7 +182,7 @@ def test_run(args):
     for spec in specs:
         matching = spack.store.STORE.db.query_local(spec, hashes=hashes, explicit=explicit)
         if spec and not matching:
-            tty.warn("No {0}installed packages match spec {1}".format(explicit_str, spec))
+            tty.warn(f"No {explicit_str}installed packages match spec {spec}")
 
             # TODO: Need to write out a log message and/or CDASH Testing
             #   output that package not installed IF continue to process
@@ -192,7 +198,7 @@ def test_run(args):
     # test_stage_dir
     test_suite = spack.install_test.TestSuite(specs_to_test, args.alias)
     test_suite.ensure_stage()
-    tty.msg("Spack test %s" % test_suite.name)
+    tty.msg(f"Spack test {test_suite.name}")
 
     # Set up reporter
     setattr(args, "package", [s.format() for s in test_suite.specs])
@@ -204,6 +210,7 @@ def test_run(args):
             dirty=args.dirty,
             fail_first=args.fail_first,
             externals=args.externals,
+            timeout=args.timeout,
         )
 
 

lib/spack/spack/compilers/adaptor.py

@@ -18,6 +18,10 @@ class Languages(enum.Enum):
 
 
 class CompilerAdaptor:
+    """Provides access to compiler attributes via `Package.compiler`. Useful for
+    packages which do not yet access compiler properties via `self.spec[language]`.
+    """
+
     def __init__(
         self, compiled_spec: spack.spec.Spec, compilers: Dict[Languages, spack.spec.Spec]
     ) -> None:
@@ -79,6 +83,14 @@ def implicit_rpaths(self) -> List[str]:
             result.extend(CompilerPropertyDetector(compiler).implicit_rpaths())
         return result
 
+    @property
+    def opt_flags(self) -> List[str]:
+        return next(iter(self.compilers.values())).package.opt_flags
+
+    @property
+    def debug_flags(self) -> List[str]:
+        return next(iter(self.compilers.values())).package.debug_flags
+
     @property
     def openmp_flag(self) -> str:
         return next(iter(self.compilers.values())).package.openmp_flag
@@ -140,7 +152,7 @@ def c17_flag(self) -> str:
     @property
     def c23_flag(self) -> str:
         return self.compilers[Languages.C].package.standard_flag(
-            language=Languages.C.value, standard="17"
+            language=Languages.C.value, standard="23"
         )
 
     @property
@@ -190,6 +202,10 @@ def f77(self):
         self._lang_exists_or_raise("f77", lang=Languages.FORTRAN)
         return self.compilers[Languages.FORTRAN].package.fortran
 
+    @property
+    def stdcxx_libs(self):
+        return self._maybe_return_attribute("stdcxx_libs", lang=Languages.CXX)
+
 
 class DeprecatedCompiler(lang.DeprecatedProperty):
     def __init__(self) -> None:

lib/spack/spack/compilers/config.py

@@ -7,6 +7,7 @@
 import os
 import re
 import sys
+import warnings
 from typing import Any, Dict, List, Optional, Tuple
 
 import archspec.cpu
@@ -337,7 +338,15 @@ def from_legacy_yaml(compiler_dict: Dict[str, Any]) -> List[spack.spec.Spec]:
             pkg_cls = spack.repo.PATH.get_pkg_class(pkg_name)
             pattern = re.compile(r"|".join(finder.search_patterns(pkg=pkg_cls)))
             filtered_paths = [x for x in candidate_paths if pattern.search(os.path.basename(x))]
-            detected = finder.detect_specs(pkg=pkg_cls, paths=filtered_paths)
+            try:
+                detected = finder.detect_specs(pkg=pkg_cls, paths=filtered_paths)
+            except Exception:
+                warnings.warn(
+                    f"[{__name__}] cannot detect {pkg_name} from the "
+                    f"following paths: {', '.join(filtered_paths)}"
+                )
+                continue
+
             for s in detected:
                 for key in ("flags", "environment", "extra_rpaths"):
                     if key in compiler_dict:

lib/spack/spack/database.py

@@ -149,12 +149,12 @@ def _getfqdn():
     return socket.getfqdn()
 
 
-def reader(version: vn.ConcreteVersion) -> Type["spack.spec.SpecfileReaderBase"]:
+def reader(version: vn.StandardVersion) -> Type["spack.spec.SpecfileReaderBase"]:
     reader_cls = {
-        vn.Version("5"): spack.spec.SpecfileV1,
-        vn.Version("6"): spack.spec.SpecfileV3,
-        vn.Version("7"): spack.spec.SpecfileV4,
-        vn.Version("8"): spack.spec.SpecfileV5,
+        vn.StandardVersion.from_string("5"): spack.spec.SpecfileV1,
+        vn.StandardVersion.from_string("6"): spack.spec.SpecfileV3,
+        vn.StandardVersion.from_string("7"): spack.spec.SpecfileV4,
+        vn.StandardVersion.from_string("8"): spack.spec.SpecfileV5,
     }
     return reader_cls[version]
 
@@ -824,7 +824,7 @@ def check(cond, msg):
         db = fdata["database"]
         check("version" in db, "no 'version' in JSON DB.")
 
-        self.db_version = vn.Version(db["version"])
+        self.db_version = vn.StandardVersion.from_string(db["version"])
         if self.db_version > _DB_VERSION:
             raise InvalidDatabaseVersionError(self, _DB_VERSION, self.db_version)
         elif self.db_version < _DB_VERSION:

lib/spack/spack/detection/common.py

@@ -20,7 +20,7 @@
 import sys
 from typing import Dict, List, Optional, Set, Tuple, Union
 
-import llnl.util.tty
+from llnl.util import tty
 
 import spack.config
 import spack.error
@@ -93,14 +93,13 @@ def _spec_is_valid(spec: spack.spec.Spec) -> bool:
     except spack.error.SpackError:
         # It is assumed here that we can at least extract the package name from the spec so we
         # can look up the implementation of determine_spec_details
-        msg = f"Constructed spec for {spec.name} does not have a string representation"
-        llnl.util.tty.warn(msg)
+        tty.warn(f"Constructed spec for {spec.name} does not have a string representation")
         return False
 
     try:
         spack.spec.Spec(str(spec))
     except spack.error.SpackError:
-        llnl.util.tty.warn(
+        tty.warn(
             "Constructed spec has a string representation but the string"
             " representation does not evaluate to a valid spec: {0}".format(str(spec))
         )
@@ -109,20 +108,24 @@ def _spec_is_valid(spec: spack.spec.Spec) -> bool:
     return True
 
 
-def path_to_dict(search_paths: List[str]):
+def path_to_dict(search_paths: List[str]) -> Dict[str, str]:
     """Return dictionary[fullpath]: basename from list of paths"""
-    path_to_lib = {}
+    path_to_lib: Dict[str, str] = {}
     # Reverse order of search directories so that a lib in the first
     # entry overrides later entries
     for search_path in reversed(search_paths):
         try:
-            with os.scandir(search_path) as entries:
-                path_to_lib.update(
-                    {entry.path: entry.name for entry in entries if entry.is_file()}
-                )
+            dir_iter = os.scandir(search_path)
         except OSError as e:
-            msg = f"cannot scan '{search_path}' for external software: {str(e)}"
-            llnl.util.tty.debug(msg)
+            tty.debug(f"cannot scan '{search_path}' for external software: {e}")
+            continue
+        with dir_iter as entries:
+            for entry in entries:
+                try:
+                    if entry.is_file():
+                        path_to_lib[entry.path] = entry.name
+                except OSError as e:
+                    tty.debug(f"cannot scan '{search_path}' for external software: {e}")
 
     return path_to_lib
 

lib/spack/spack/directives.py

@@ -34,11 +34,13 @@ class OpenMpi(Package):
 import collections.abc
 import os
 import re
+import warnings
 from typing import Any, Callable, List, Optional, Tuple, Type, Union
 
 import llnl.util.tty.color
 
 import spack.deptypes as dt
+import spack.error
 import spack.fetch_strategy
 import spack.package_base
 import spack.patch
@@ -608,7 +610,7 @@ def _execute_patch(
     return _execute_patch
 
 
-def conditional(*values: List[Any], when: Optional[WhenType] = None):
+def conditional(*values: Union[str, bool], when: Optional[WhenType] = None):
     """Conditional values that can be used in variant declarations."""
     # _make_when_spec returns None when the condition is statically false.
     when = _make_when_spec(when)
@@ -620,7 +622,7 @@ def conditional(*values: List[Any], when: Optional[WhenType] = None):
 @directive("variants")
 def variant(
     name: str,
-    default: Optional[Any] = None,
+    default: Optional[Union[bool, str, Tuple[str, ...]]] = None,
     description: str = "",
     values: Optional[Union[collections.abc.Sequence, Callable[[Any], bool]]] = None,
     multi: Optional[bool] = None,
@@ -650,11 +652,29 @@ def variant(
         DirectiveError: If arguments passed to the directive are invalid
     """
 
+    # This validation can be removed at runtime and enforced with an audit in Spack v1.0.
+    # For now it's a warning to let people migrate faster.
+    if not (
+        default is None
+        or type(default) in (bool, str)
+        or (type(default) is tuple and all(type(x) is str for x in default))
+    ):
+        if isinstance(default, (list, tuple)):
+            did_you_mean = f"default={','.join(str(x) for x in default)!r}"
+        else:
+            did_you_mean = f"default={str(default)!r}"
+        warnings.warn(
+            f"default value for variant '{name}' is not a boolean or string: default={default!r}. "
+            f"Did you mean {did_you_mean}?",
+            stacklevel=3,
+            category=spack.error.SpackAPIWarning,
+        )
+
     def format_error(msg, pkg):
         msg += " @*r{{[{0}, variant '{1}']}}"
         return llnl.util.tty.color.colorize(msg.format(pkg.name, name))
 
-    if name in spack.variant.reserved_names:
+    if name in spack.variant.RESERVED_NAMES:
 
         def _raise_reserved_name(pkg):
             msg = "The name '%s' is reserved by Spack" % name
@@ -665,7 +685,11 @@ def _raise_reserved_name(pkg):
     # Ensure we have a sequence of allowed variant values, or a
     # predicate for it.
     if values is None:
-        if str(default).upper() in ("TRUE", "FALSE"):
+        if (
+            default in (True, False)
+            or type(default) is str
+            and default.upper() in ("TRUE", "FALSE")
+        ):
             values = (True, False)
         else:
             values = lambda x: True
@@ -698,12 +722,15 @@ def _raise_argument_error(pkg):
     # or the empty string, as the former indicates that a default
     # was not set while the latter will make the variant unparsable
     # from the command line
+    if isinstance(default, tuple):
+        default = ",".join(default)
+
     if default is None or default == "":
 
         def _raise_default_not_set(pkg):
             if default is None:
-                msg = "either a default was not explicitly set, " "or 'None' was used"
-            elif default == "":
+                msg = "either a default was not explicitly set, or 'None' was used"
+            else:
                 msg = "the default cannot be an empty string"
             raise DirectiveError(format_error(msg, pkg))
 

lib/spack/spack/directives_meta.py

@@ -65,7 +65,7 @@ def __init__(cls: "DirectiveMeta", name: str, bases: tuple, attr_dict: dict):
         # The instance is being initialized: if it is a package we must ensure
         # that the directives are called to set it up.
 
-        if cls.__module__.startswith(spack.repo.ROOT_PYTHON_NAMESPACE):
+        if spack.repo.is_package_module(cls.__module__):
             # Ensure the presence of the dictionaries associated with the directives.
             # All dictionaries are defaultdicts that create lists for missing keys.
             for d in DirectiveMeta._directive_dict_names:
@@ -144,7 +144,6 @@ class Foo(Package):
         Package class, and it's how Spack gets information from the
         packages to the core.
         """
-        global directive_names
 
         if isinstance(dicts, str):
             dicts = (dicts,)

lib/spack/spack/environment/__init__.py

@@ -566,7 +566,7 @@
     display_specs,
     environment_dir_from_name,
     environment_from_name_or_dir,
-    environment_path_scopes,
+    environment_path_scope,
     exists,
     initialize_environment_dir,
     installed_specs,
@@ -603,7 +603,7 @@
     "display_specs",
     "environment_dir_from_name",
     "environment_from_name_or_dir",
-    "environment_path_scopes",
+    "environment_path_scope",
     "exists",
     "initialize_environment_dir",
     "installed_specs",

lib/spack/spack/environment/environment.py

@@ -31,7 +31,6 @@
 import spack.repo
 import spack.schema.env
 import spack.spec
-import spack.spec_list
 import spack.store
 import spack.user_environment as uenv
 import spack.util.environment
@@ -44,10 +43,10 @@
 from spack.installer import PackageInstaller
 from spack.schema.env import TOP_LEVEL_KEY
 from spack.spec import Spec
-from spack.spec_list import SpecList
 from spack.util.path import substitute_path_variables
 
 from ..enums import ConfigScopePriority
+from .list import SpecList, SpecListError, SpecListParser
 
 SpecPair = spack.concretize.SpecPair
 
@@ -97,16 +96,15 @@ def environment_name(path: Union[str, pathlib.Path]) -> str:
         return path_str
 
 
-def ensure_no_disallowed_env_config_mods(scopes: List[spack.config.ConfigScope]) -> None:
-    for scope in scopes:
-        config = scope.get_section("config")
-        if config and "environments_root" in config["config"]:
-            raise SpackEnvironmentError(
-                "Spack environments are prohibited from modifying 'config:environments_root' "
-                "because it can make the definition of the environment ill-posed. Please "
-                "remove from your environment and place it in a permanent scope such as "
-                "defaults, system, site, etc."
-            )
+def ensure_no_disallowed_env_config_mods(scope: spack.config.ConfigScope) -> None:
+    config = scope.get_section("config")
+    if config and "environments_root" in config["config"]:
+        raise SpackEnvironmentError(
+            "Spack environments are prohibited from modifying 'config:environments_root' "
+            "because it can make the definition of the environment ill-posed. Please "
+            "remove from your environment and place it in a permanent scope such as "
+            "defaults, system, site, etc."
+        )
 
 
 def default_manifest_yaml():
@@ -933,8 +931,10 @@ def __init__(self, manifest_dir: Union[str, pathlib.Path]) -> None:
         self.new_specs: List[Spec] = []
         self.views: Dict[str, ViewDescriptor] = {}
 
+        #: Parser for spec lists
+        self._spec_lists_parser = SpecListParser()
         #: Specs from "spack.yaml"
-        self.spec_lists: Dict[str, SpecList] = {user_speclist_name: SpecList()}
+        self.spec_lists: Dict[str, SpecList] = {}
         #: User specs from the last concretization
         self.concretized_user_specs: List[Spec] = []
         #: Roots associated with the last concretization, in order
@@ -1002,26 +1002,6 @@ def write_transaction(self):
         """Get a write lock context manager for use in a `with` block."""
         return lk.WriteTransaction(self.txlock, acquire=self._re_read)
 
-    def _process_definition(self, entry):
-        """Process a single spec definition item."""
-        when_string = entry.get("when")
-        if when_string is not None:
-            when = spack.spec.eval_conditional(when_string)
-            assert len([x for x in entry if x != "when"]) == 1
-        else:
-            when = True
-            assert len(entry) == 1
-
-        if when:
-            for name, spec_list in entry.items():
-                if name == "when":
-                    continue
-                user_specs = SpecList(name, spec_list, self.spec_lists.copy())
-                if name in self.spec_lists:
-                    self.spec_lists[name].extend(user_specs)
-                else:
-                    self.spec_lists[name] = user_specs
-
     def _process_view(self, env_view: Optional[Union[bool, str, Dict]]):
         """Process view option(s), which can be boolean, string, or None.
 
@@ -1083,21 +1063,24 @@ def _process_concrete_includes(self):
 
     def _construct_state_from_manifest(self):
         """Set up user specs and views from the manifest file."""
-        self.spec_lists = collections.OrderedDict()
         self.views = {}
+        self._sync_speclists()
+        self._process_view(spack.config.get("view", True))
+        self._process_concrete_includes()
 
-        for item in spack.config.get("definitions", []):
-            self._process_definition(item)
+    def _sync_speclists(self):
+        self.spec_lists = {}
+        self.spec_lists.update(
+            self._spec_lists_parser.parse_definitions(
+                data=spack.config.CONFIG.get("definitions", [])
+            )
+        )
 
         env_configuration = self.manifest[TOP_LEVEL_KEY]
         spec_list = env_configuration.get(user_speclist_name, [])
-        user_specs = SpecList(
-            user_speclist_name, [s for s in spec_list if s], self.spec_lists.copy()
+        self.spec_lists[user_speclist_name] = self._spec_lists_parser.parse_user_specs(
+            name=user_speclist_name, yaml_list=spec_list
         )
-        self.spec_lists[user_speclist_name] = user_specs
-
-        self._process_view(spack.config.get("view", True))
-        self._process_concrete_includes()
 
     def all_concretized_user_specs(self) -> List[Spec]:
         """Returns all of the concretized user specs of the environment and
@@ -1168,9 +1151,7 @@ def clear(self, re_read=False):
             re_read: If ``True``, do not clear ``new_specs``. This value cannot be read from yaml,
                 and needs to be maintained when re-reading an existing environment.
         """
-        self.spec_lists = collections.OrderedDict()
-        self.spec_lists[user_speclist_name] = SpecList()
-
+        self.spec_lists = {}
         self._dev_specs = {}
         self.concretized_order = []  # roots of last concretize, in order
         self.concretized_user_specs = []  # user specs from last concretize
@@ -1277,22 +1258,6 @@ def destroy(self):
         """Remove this environment from Spack entirely."""
         shutil.rmtree(self.path)
 
-    def update_stale_references(self, from_list=None):
-        """Iterate over spec lists updating references."""
-        if not from_list:
-            from_list = next(iter(self.spec_lists.keys()))
-        index = list(self.spec_lists.keys()).index(from_list)
-
-        # spec_lists is an OrderedDict to ensure lists read from the manifest
-        # are maintainted in order, hence, all list entries after the modified
-        # list may refer to the modified list requiring stale references to be
-        # updated.
-        for i, (name, speclist) in enumerate(
-            list(self.spec_lists.items())[index + 1 :], index + 1
-        ):
-            new_reference = dict((n, self.spec_lists[n]) for n in list(self.spec_lists.keys())[:i])
-            speclist.update_reference(new_reference)
-
     def add(self, user_spec, list_name=user_speclist_name):
         """Add a single user_spec (non-concretized) to the Environment
 
@@ -1312,18 +1277,17 @@ def add(self, user_spec, list_name=user_speclist_name):
             elif not spack.repo.PATH.exists(spec.name) and not spec.abstract_hash:
                 virtuals = spack.repo.PATH.provider_index.providers.keys()
                 if spec.name not in virtuals:
-                    msg = "no such package: %s" % spec.name
-                    raise SpackEnvironmentError(msg)
+                    raise SpackEnvironmentError(f"no such package: {spec.name}")
 
         list_to_change = self.spec_lists[list_name]
         existing = str(spec) in list_to_change.yaml_list
         if not existing:
             list_to_change.add(str(spec))
-            self.update_stale_references(list_name)
             if list_name == user_speclist_name:
                 self.manifest.add_user_spec(str(user_spec))
             else:
                 self.manifest.add_definition(str(user_spec), list_name=list_name)
+            self._sync_speclists()
 
         return bool(not existing)
 
@@ -1367,18 +1331,17 @@ def change_existing_spec(
                 "There are no specs named {0} in {1}".format(match_spec.name, list_name)
             )
         elif len(matches) > 1 and not allow_changing_multiple_specs:
-            raise ValueError("{0} matches multiple specs".format(str(match_spec)))
+            raise ValueError(f"{str(match_spec)} matches multiple specs")
 
         for idx, spec in matches:
             override_spec = Spec.override(spec, change_spec)
-            self.spec_lists[list_name].replace(idx, str(override_spec))
             if list_name == user_speclist_name:
                 self.manifest.override_user_spec(str(override_spec), idx=idx)
             else:
                 self.manifest.override_definition(
                     str(spec), override=str(override_spec), list_name=list_name
                 )
-        self.update_stale_references(from_list=list_name)
+        self._sync_speclists()
 
     def remove(self, query_spec, list_name=user_speclist_name, force=False):
         """Remove specs from an environment that match a query_spec"""
@@ -1406,22 +1369,17 @@ def remove(self, query_spec, list_name=user_speclist_name, force=False):
             raise SpackEnvironmentError(f"{err_msg_header}, no spec matches")
 
         old_specs = set(self.user_specs)
-        new_specs = set()
+
+        # Remove specs from the appropriate spec list
         for spec in matches:
             if spec not in list_to_change:
                 continue
             try:
                 list_to_change.remove(spec)
-                self.update_stale_references(list_name)
-                new_specs = set(self.user_specs)
-            except spack.spec_list.SpecListError as e:
-                # define new specs list
-                new_specs = set(self.user_specs)
+            except SpecListError as e:
                 msg = str(e)
                 if force:
                     msg += " It will be removed from the concrete specs."
-                    # Mock new specs, so we can remove this spec from concrete spec lists
-                    new_specs.remove(spec)
                 tty.warn(msg)
             else:
                 if list_name == user_speclist_name:
@@ -1429,7 +1387,11 @@ def remove(self, query_spec, list_name=user_speclist_name, force=False):
                 else:
                     self.manifest.remove_definition(str(spec), list_name=list_name)
 
-        # If force, update stale concretized specs
+        # Recompute "definitions" and user specs
+        self._sync_speclists()
+        new_specs = set(self.user_specs)
+
+        # If 'force', update stale concretized specs
         for spec in old_specs - new_specs:
             if force and spec in self.concretized_user_specs:
                 i = self.concretized_user_specs.index(spec)
@@ -1643,23 +1605,6 @@ def _concretize_separately(self, tests=False):
 
         # Unify the specs objects, so we get correct references to all parents
         self._read_lockfile_dict(self._to_lockfile_dict())
-
-        # Re-attach information on test dependencies
-        if tests:
-            # This is slow, but the information on test dependency is lost
-            # after unification or when reading from a lockfile.
-            for h in self.specs_by_hash:
-                current_spec, computed_spec = self.specs_by_hash[h], by_hash[h]
-                for node in computed_spec.traverse():
-                    test_edges = node.edges_to_dependencies(depflag=dt.TEST)
-                    for current_edge in test_edges:
-                        test_dependency = current_edge.spec
-                        if test_dependency in current_spec[node.name]:
-                            continue
-                        current_spec[node.name].add_dependency_edge(
-                            test_dependency.copy(), depflag=dt.TEST, virtuals=current_edge.virtuals
-                        )
-
         return concretized_specs
 
     @property
@@ -2367,8 +2312,12 @@ def update_environment_repository(self) -> None:
 
     def _add_to_environment_repository(self, spec_node: Spec) -> None:
         """Add the root node of the spec to the environment repository"""
-        repository_dir = os.path.join(self.repos_path, spec_node.namespace)
-        repository = spack.repo.create_or_construct(repository_dir, spec_node.namespace)
+        namespace: str = spec_node.namespace
+        repository = spack.repo.create_or_construct(
+            root=os.path.join(self.repos_path, namespace),
+            namespace=namespace,
+            package_api=spack.repo.PATH.get_repo(namespace).package_api,
+        )
         pkg_dir = repository.dirname_for_package_name(spec_node.name)
         fs.mkdirp(pkg_dir)
         spack.repo.PATH.dump_provenance(spec_node, pkg_dir)
@@ -2717,9 +2666,9 @@ def __init__(self, manifest_dir: Union[pathlib.Path, str], name: Optional[str] =
         self.scope_name = f"env:{self.name}"
         self.config_stage_dir = os.path.join(env_subdir_path(manifest_dir), "config")
 
-        #: Configuration scopes associated with this environment. Note that these are not
+        #: Configuration scope associated with this environment. Note that this is not
         #: invalidated by a re-read of the manifest file.
-        self._config_scopes: Optional[List[spack.config.ConfigScope]] = None
+        self._env_config_scope: Optional[spack.config.ConfigScope] = None
 
         if not self.manifest_file.exists():
             msg = f"cannot find '{manifest_name}' in {self.manifest_dir}"
@@ -2828,6 +2777,8 @@ def add_definition(self, user_spec: str, list_name: str) -> None:
             item[list_name].append(user_spec)
             break
 
+        # "definitions" can be remote, so we need to update the global config too
+        spack.config.CONFIG.set("definitions", defs, scope=self.scope_name)
         self.changed = True
 
     def remove_definition(self, user_spec: str, list_name: str) -> None:
@@ -2854,6 +2805,8 @@ def remove_definition(self, user_spec: str, list_name: str) -> None:
             except ValueError:
                 pass
 
+        # "definitions" can be remote, so we need to update the global config too
+        spack.config.CONFIG.set("definitions", defs, scope=self.scope_name)
         self.changed = True
 
     def override_definition(self, user_spec: str, *, override: str, list_name: str) -> None:
@@ -2879,6 +2832,8 @@ def override_definition(self, user_spec: str, *, override: str, list_name: str)
             except ValueError:
                 pass
 
+        # "definitions" can be remote, so we need to update the global config too
+        spack.config.CONFIG.set("definitions", defs, scope=self.scope_name)
         self.changed = True
 
     def _iterate_on_definitions(self, definitions, *, list_name, err_msg):
@@ -2957,33 +2912,27 @@ def __str__(self):
         return str(self.manifest_file)
 
     @property
-    def env_config_scopes(self) -> List[spack.config.ConfigScope]:
-        """A list of all configuration scopes for the environment manifest. On the first call this
-        instantiates all the scopes, on subsequent calls it returns the cached list."""
-        if self._config_scopes is not None:
-            return self._config_scopes
-
-        scopes: List[spack.config.ConfigScope] = [
-            spack.config.SingleFileScope(
+    def env_config_scope(self) -> spack.config.ConfigScope:
+        """The configuration scope for the environment manifest"""
+        if self._env_config_scope is None:
+            self._env_config_scope = spack.config.SingleFileScope(
                 self.scope_name,
                 str(self.manifest_file),
                 spack.schema.env.schema,
                 yaml_path=[TOP_LEVEL_KEY],
             )
-        ]
-        ensure_no_disallowed_env_config_mods(scopes)
-        self._config_scopes = scopes
-        return scopes
+            ensure_no_disallowed_env_config_mods(self._env_config_scope)
+        return self._env_config_scope
 
     def prepare_config_scope(self) -> None:
-        """Add the manifest's scopes to the global configuration search path."""
-        for scope in self.env_config_scopes:
-            spack.config.CONFIG.push_scope(scope, priority=ConfigScopePriority.ENVIRONMENT)
+        """Add the manifest's scope to the global configuration search path."""
+        spack.config.CONFIG.push_scope(
+            self.env_config_scope, priority=ConfigScopePriority.ENVIRONMENT
+        )
 
     def deactivate_config_scope(self) -> None:
-        """Remove any of the manifest's scopes from the global config path."""
-        for scope in self.env_config_scopes:
-            spack.config.CONFIG.remove_scope(scope.name)
+        """Remove the manifest's scope from the global config path."""
+        spack.config.CONFIG.remove_scope(self.env_config_scope.name)
 
     @contextlib.contextmanager
     def use_config(self):
@@ -2994,8 +2943,8 @@ def use_config(self):
             self.deactivate_config_scope()
 
 
-def environment_path_scopes(name: str, path: str) -> Optional[List[spack.config.ConfigScope]]:
-    """Retrieve the suitably named environment path scopes
+def environment_path_scope(name: str, path: str) -> Optional[spack.config.ConfigScope]:
+    """Retrieve the suitably named environment path scope
 
     Arguments:
         name: configuration scope name
@@ -3010,11 +2959,9 @@ def environment_path_scopes(name: str, path: str) -> Optional[List[spack.config.
     else:
         return None
 
-    for scope in manifest.env_config_scopes:
-        scope.name = f"{name}:{scope.name}"
-        scope.writable = False
-
-    return manifest.env_config_scopes
+    manifest.env_config_scope.name = f"{name}:{manifest.env_config_scope.name}"
+    manifest.env_config_scope.writable = False
+    return manifest.env_config_scope
 
 
 class SpackEnvironmentError(spack.error.SpackError):

lib/spack/spack/environment/list.py

@@ -0,0 +1,286 @@
+# Copyright Spack Project Developers. See COPYRIGHT file for details.
+#
+# SPDX-License-Identifier: (Apache-2.0 OR MIT)
+import itertools
+from typing import Any, Dict, List, NamedTuple, Optional, Union
+
+import spack.spec
+import spack.util.spack_yaml
+import spack.variant
+from spack.error import SpackError
+from spack.spec import Spec
+
+
+class SpecList:
+    def __init__(self, *, name: str = "specs", yaml_list=None, expanded_list=None):
+        self.name = name
+        self.yaml_list = yaml_list[:] if yaml_list is not None else []
+        # Expansions can be expensive to compute and difficult to keep updated
+        # We cache results and invalidate when self.yaml_list changes
+        self.specs_as_yaml_list = expanded_list or []
+        self._constraints = None
+        self._specs: Optional[List[Spec]] = None
+
+    @property
+    def is_matrix(self):
+        for item in self.specs_as_yaml_list:
+            if isinstance(item, dict):
+                return True
+        return False
+
+    @property
+    def specs_as_constraints(self):
+        if self._constraints is None:
+            constraints = []
+            for item in self.specs_as_yaml_list:
+                if isinstance(item, dict):  # matrix of specs
+                    constraints.extend(_expand_matrix_constraints(item))
+                else:  # individual spec
+                    constraints.append([Spec(item)])
+            self._constraints = constraints
+
+        return self._constraints
+
+    @property
+    def specs(self) -> List[Spec]:
+        if self._specs is None:
+            specs: List[Spec] = []
+            # This could be slightly faster done directly from yaml_list,
+            # but this way is easier to maintain.
+            for constraint_list in self.specs_as_constraints:
+                spec = constraint_list[0].copy()
+                for const in constraint_list[1:]:
+                    spec.constrain(const)
+                specs.append(spec)
+            self._specs = specs
+
+        return self._specs
+
+    def add(self, spec: Spec):
+        spec_str = str(spec)
+        self.yaml_list.append(spec_str)
+
+        # expanded list can be updated without invalidation
+        if self.specs_as_yaml_list is not None:
+            self.specs_as_yaml_list.append(spec_str)
+
+        # Invalidate cache variables when we change the list
+        self._constraints = None
+        self._specs = None
+
+    def remove(self, spec):
+        # Get spec to remove from list
+        remove = [
+            s
+            for s in self.yaml_list
+            if (isinstance(s, str) and not s.startswith("$")) and Spec(s) == Spec(spec)
+        ]
+        if not remove:
+            msg = f"Cannot remove {spec} from SpecList {self.name}.\n"
+            msg += f"Either {spec} is not in {self.name} or {spec} is "
+            msg += "expanded from a matrix and cannot be removed directly."
+            raise SpecListError(msg)
+
+        # Remove may contain more than one string representation of the same spec
+        for item in remove:
+            self.yaml_list.remove(item)
+            self.specs_as_yaml_list.remove(item)
+
+        # invalidate cache variables when we change the list
+        self._constraints = None
+        self._specs = None
+
+    def extend(self, other: "SpecList", copy_reference=True) -> None:
+        self.yaml_list.extend(other.yaml_list)
+        self.specs_as_yaml_list.extend(other.specs_as_yaml_list)
+        self._constraints = None
+        self._specs = None
+
+    def __len__(self):
+        return len(self.specs)
+
+    def __getitem__(self, key):
+        return self.specs[key]
+
+    def __iter__(self):
+        return iter(self.specs)
+
+
+def _expand_matrix_constraints(matrix_config):
+    # recurse so we can handle nested matrices
+    expanded_rows = []
+    for row in matrix_config["matrix"]:
+        new_row = []
+        for r in row:
+            if isinstance(r, dict):
+                # Flatten the nested matrix into a single row of constraints
+                new_row.extend(
+                    [
+                        [" ".join([str(c) for c in expanded_constraint_list])]
+                        for expanded_constraint_list in _expand_matrix_constraints(r)
+                    ]
+                )
+            else:
+                new_row.append([r])
+        expanded_rows.append(new_row)
+
+    excludes = matrix_config.get("exclude", [])  # only compute once
+    sigil = matrix_config.get("sigil", "")
+
+    results = []
+    for combo in itertools.product(*expanded_rows):
+        # Construct a combined spec to test against excludes
+        flat_combo = [Spec(constraint) for constraints in combo for constraint in constraints]
+
+        test_spec = flat_combo[0].copy()
+        for constraint in flat_combo[1:]:
+            test_spec.constrain(constraint)
+
+        # Abstract variants don't have normal satisfaction semantics
+        # Convert all variants to concrete types.
+        # This method is best effort, so all existing variants will be
+        # converted before any error is raised.
+        # Catch exceptions because we want to be able to operate on
+        # abstract specs without needing package information
+        try:
+            spack.spec.substitute_abstract_variants(test_spec)
+        except spack.variant.UnknownVariantError:
+            pass
+
+        # Resolve abstract hashes for exclusion criteria
+        if any(test_spec.lookup_hash().satisfies(x) for x in excludes):
+            continue
+
+        if sigil:
+            flat_combo[0] = Spec(sigil + str(flat_combo[0]))
+
+        # Add to list of constraints
+        results.append(flat_combo)
+
+    return results
+
+
+def _sigilify(item, sigil):
+    if isinstance(item, dict):
+        if sigil:
+            item["sigil"] = sigil
+        return item
+    else:
+        return sigil + item
+
+
+class Definition(NamedTuple):
+    name: str
+    yaml_list: List[Union[str, Dict]]
+    when: Optional[str]
+
+
+class SpecListParser:
+    """Parse definitions and user specs from data in environments"""
+
+    def __init__(self):
+        self.definitions: Dict[str, SpecList] = {}
+
+    def parse_definitions(self, *, data: List[Dict[str, Any]]) -> Dict[str, SpecList]:
+        definitions_from_yaml: Dict[str, List[Definition]] = {}
+        for item in data:
+            value = self._parse_yaml_definition(item)
+            definitions_from_yaml.setdefault(value.name, []).append(value)
+
+        self.definitions = {}
+        self._build_definitions(definitions_from_yaml)
+        return self.definitions
+
+    def parse_user_specs(self, *, name, yaml_list) -> SpecList:
+        definition = Definition(name=name, yaml_list=yaml_list, when=None)
+        return self._speclist_from_definitions(name, [definition])
+
+    def _parse_yaml_definition(self, yaml_entry) -> Definition:
+        when_string = yaml_entry.get("when")
+
+        if (when_string and len(yaml_entry) > 2) or (not when_string and len(yaml_entry) > 1):
+            mark = spack.util.spack_yaml.get_mark_from_yaml_data(yaml_entry)
+            attributes = ", ".join(x for x in yaml_entry if x != "when")
+            error_msg = f"definition must have a single attribute, got many: {attributes}"
+            raise SpecListError(f"{mark.name}:{mark.line + 1}: {error_msg}")
+
+        for name, yaml_list in yaml_entry.items():
+            if name == "when":
+                continue
+            return Definition(name=name, yaml_list=yaml_list, when=when_string)
+
+        # If we are here, it means only "when" is in the entry
+        mark = spack.util.spack_yaml.get_mark_from_yaml_data(yaml_entry)
+        error_msg = "definition must have a single attribute, got none"
+        raise SpecListError(f"{mark.name}:{mark.line + 1}: {error_msg}")
+
+    def _build_definitions(self, definitions_from_yaml: Dict[str, List[Definition]]):
+        for name, definitions in definitions_from_yaml.items():
+            self.definitions[name] = self._speclist_from_definitions(name, definitions)
+
+    def _speclist_from_definitions(self, name, definitions) -> SpecList:
+        combined_yaml_list = []
+        for def_part in definitions:
+            if def_part.when is not None and not spack.spec.eval_conditional(def_part.when):
+                continue
+            combined_yaml_list.extend(def_part.yaml_list)
+        expanded_list = self._expand_yaml_list(combined_yaml_list)
+        return SpecList(name=name, yaml_list=combined_yaml_list, expanded_list=expanded_list)
+
+    def _expand_yaml_list(self, raw_yaml_list):
+        result = []
+        for item in raw_yaml_list:
+            if isinstance(item, str) and item.startswith("$"):
+                result.extend(self._expand_reference(item))
+                continue
+
+            value = item
+            if isinstance(item, dict):
+                value = self._expand_yaml_matrix(item)
+            result.append(value)
+        return result
+
+    def _expand_reference(self, item: str):
+        sigil, name = "", item[1:]
+        if name.startswith("^") or name.startswith("%"):
+            sigil, name = name[0], name[1:]
+
+        if name not in self.definitions:
+            mark = spack.util.spack_yaml.get_mark_from_yaml_data(item)
+            error_msg = f"trying to expand the name '{name}', which is not defined yet"
+            raise UndefinedReferenceError(f"{mark.name}:{mark.line + 1}: {error_msg}")
+
+        value = self.definitions[name].specs_as_yaml_list
+        if not sigil:
+            return value
+        return [_sigilify(x, sigil) for x in value]
+
+    def _expand_yaml_matrix(self, matrix_yaml):
+        extra_attributes = set(matrix_yaml) - {"matrix", "exclude"}
+        if extra_attributes:
+            mark = spack.util.spack_yaml.get_mark_from_yaml_data(matrix_yaml)
+            error_msg = f"extra attributes in spec matrix: {','.join(sorted(extra_attributes))}"
+            raise SpecListError(f"{mark.name}:{mark.line + 1}: {error_msg}")
+
+        if "matrix" not in matrix_yaml:
+            mark = spack.util.spack_yaml.get_mark_from_yaml_data(matrix_yaml)
+            error_msg = "matrix is missing the 'matrix' attribute"
+            raise SpecListError(f"{mark.name}:{mark.line + 1}: {error_msg}")
+
+        # Assume data has been validated against the YAML schema
+        result = {"matrix": [self._expand_yaml_list(row) for row in matrix_yaml["matrix"]]}
+        if "exclude" in matrix_yaml:
+            result["exclude"] = matrix_yaml["exclude"]
+        return result
+
+
+class SpecListError(SpackError):
+    """Error class for all errors related to SpecList objects."""
+
+
+class UndefinedReferenceError(SpecListError):
+    """Error class for undefined references in Spack stacks."""
+
+
+class InvalidSpecConstraintError(SpecListError):
+    """Error class for invalid spec constraints at concretize time."""

lib/spack/spack/environment/shell.py

@@ -49,10 +49,23 @@ def activate_header(env, shell, prompt=None, view: Optional[str] = None):
         cmds += 'set "SPACK_ENV=%s"\n' % env.path
         if view:
             cmds += 'set "SPACK_ENV_VIEW=%s"\n' % view
+        if prompt:
+            old_prompt = os.environ.get("SPACK_OLD_PROMPT")
+            if not old_prompt:
+                old_prompt = os.environ.get("PROMPT")
+            cmds += f'set "SPACK_OLD_PROMPT={old_prompt}"\n'
+            cmds += f'set "PROMPT={prompt} $P$G"\n'
     elif shell == "pwsh":
         cmds += "$Env:SPACK_ENV='%s'\n" % env.path
         if view:
             cmds += "$Env:SPACK_ENV_VIEW='%s'\n" % view
+        if prompt:
+            cmds += (
+                "function global:prompt { $pth = $(Convert-Path $(Get-Location))"
+                ' | Split-Path -leaf; if(!"$Env:SPACK_OLD_PROMPT") '
+                '{$Env:SPACK_OLD_PROMPT="[spack] PS $pth>"}; '
+                '"%s PS $pth>"}\n' % prompt
+            )
     else:
         bash_color_prompt = colorize(f"@G{{{prompt}}}", color=True, enclose=True)
         zsh_color_prompt = colorize(f"@G{{{prompt}}}", color=True, enclose=False, zsh=True)
@@ -107,10 +120,19 @@ def deactivate_header(shell):
         cmds += 'set "SPACK_ENV="\n'
         cmds += 'set "SPACK_ENV_VIEW="\n'
         # TODO: despacktivate
-        # TODO: prompt
+        old_prompt = os.environ.get("SPACK_OLD_PROMPT")
+        if old_prompt:
+            cmds += f'set "PROMPT={old_prompt}"\n'
+            cmds += 'set "SPACK_OLD_PROMPT="\n'
     elif shell == "pwsh":
         cmds += "Set-Item -Path Env:SPACK_ENV\n"
         cmds += "Set-Item -Path Env:SPACK_ENV_VIEW\n"
+        cmds += (
+            "function global:prompt { $pth = $(Convert-Path $(Get-Location))"
+            ' | Split-Path -leaf; $spack_prompt = "[spack] $pth >"; '
+            'if("$Env:SPACK_OLD_PROMPT") {$spack_prompt=$Env:SPACK_OLD_PROMPT};'
+            " $spack_prompt}\n"
+        )
     else:
         cmds += "if [ ! -z ${SPACK_ENV+x} ]; then\n"
         cmds += "unset SPACK_ENV; export SPACK_ENV;\n"

lib/spack/spack/fetch_strategy.py

@@ -27,11 +27,14 @@
 import os
 import re
 import shutil
+import sys
+import time
 import urllib.error
 import urllib.parse
 import urllib.request
+import urllib.response
 from pathlib import PurePath
-from typing import List, Optional
+from typing import Callable, List, Mapping, Optional
 
 import llnl.url
 import llnl.util
@@ -219,6 +222,114 @@ def mirror_id(self):
         """BundlePackages don't have a mirror id."""
 
 
+def _format_speed(total_bytes: int, elapsed: float) -> str:
+    """Return a human-readable average download speed string."""
+    elapsed = 1 if elapsed <= 0 else elapsed  # avoid divide by zero
+    speed = total_bytes / elapsed
+    if speed >= 1e9:
+        return f"{speed / 1e9:6.1f} GB/s"
+    elif speed >= 1e6:
+        return f"{speed / 1e6:6.1f} MB/s"
+    elif speed >= 1e3:
+        return f"{speed / 1e3:6.1f} KB/s"
+    return f"{speed:6.1f}  B/s"
+
+
+def _format_bytes(total_bytes: int) -> str:
+    """Return a human-readable total bytes string."""
+    if total_bytes >= 1e9:
+        return f"{total_bytes / 1e9:7.2f} GB"
+    elif total_bytes >= 1e6:
+        return f"{total_bytes / 1e6:7.2f} MB"
+    elif total_bytes >= 1e3:
+        return f"{total_bytes / 1e3:7.2f} KB"
+    return f"{total_bytes:7.2f}  B"
+
+
+class FetchProgress:
+    #: Characters to rotate in the spinner.
+    spinner = ["|", "/", "-", "\\"]
+
+    def __init__(
+        self,
+        total_bytes: Optional[int] = None,
+        enabled: bool = True,
+        get_time: Callable[[], float] = time.time,
+    ) -> None:
+        """Initialize a FetchProgress instance.
+        Args:
+            total_bytes: Total number of bytes to download, if known.
+            enabled: Whether to print progress information.
+            get_time: Function to get the current time."""
+        #: Number of bytes downloaded so far.
+        self.current_bytes = 0
+        #: Delta time between progress prints
+        self.delta = 0.1
+        #: Whether to print progress information.
+        self.enabled = enabled
+        #: Function to get the current time.
+        self.get_time = get_time
+        #: Time of last progress print to limit output
+        self.last_printed = 0.0
+        #: Time of start of download
+        self.start_time = get_time() if enabled else 0.0
+        #: Total number of bytes to download, if known.
+        self.total_bytes = total_bytes if total_bytes and total_bytes > 0 else 0
+        #: Index of spinner character to print (used if total bytes is unknown)
+        self.index = 0
+
+    @classmethod
+    def from_headers(
+        cls,
+        headers: Mapping[str, str],
+        enabled: bool = True,
+        get_time: Callable[[], float] = time.time,
+    ) -> "FetchProgress":
+        """Create a FetchProgress instance from HTTP headers."""
+        # headers.get is case-insensitive if it's from a HTTPResponse object.
+        content_length = headers.get("Content-Length")
+        try:
+            total_bytes = int(content_length) if content_length else None
+        except ValueError:
+            total_bytes = None
+        return cls(total_bytes=total_bytes, enabled=enabled, get_time=get_time)
+
+    def advance(self, num_bytes: int, out=sys.stdout) -> None:
+        if not self.enabled:
+            return
+        self.current_bytes += num_bytes
+        self.print(out=out)
+
+    def print(self, final: bool = False, out=sys.stdout) -> None:
+        if not self.enabled:
+            return
+        current_time = self.get_time()
+        if self.last_printed + self.delta < current_time or final:
+            self.last_printed = current_time
+            # print a newline if this is the final update
+            maybe_newline = "\n" if final else ""
+            # if we know the total bytes, show a percentage, otherwise a spinner
+            if self.total_bytes > 0:
+                percentage = min(100 * self.current_bytes / self.total_bytes, 100.0)
+                percent_or_spinner = f"[{percentage:3.0f}%] "
+            else:
+                # only show the spinner if we are not at 100%
+                if final:
+                    percent_or_spinner = "[100%] "
+                else:
+                    percent_or_spinner = f"[ {self.spinner[self.index]}  ] "
+                self.index = (self.index + 1) % len(self.spinner)
+
+            print(
+                f"\r    {percent_or_spinner}{_format_bytes(self.current_bytes)} "
+                f"@ {_format_speed(self.current_bytes, current_time - self.start_time)}"
+                f"{maybe_newline}",
+                end="",
+                flush=True,
+                file=out,
+            )
+
+
 @fetcher
 class URLFetchStrategy(FetchStrategy):
     """URLFetchStrategy pulls source code from a URL for an archive, check the
@@ -295,8 +406,9 @@ def fetch(self):
             )
 
     def _fetch_from_url(self, url):
-        if spack.config.get("config:url_fetch_method") == "curl":
-            return self._fetch_curl(url)
+        fetch_method = spack.config.get("config:url_fetch_method", "urllib")
+        if fetch_method.startswith("curl"):
+            return self._fetch_curl(url, config_args=fetch_method.split()[1:])
         else:
             return self._fetch_urllib(url)
 
@@ -315,7 +427,7 @@ def _check_headers(self, headers):
             tty.warn(msg)
 
     @_needs_stage
-    def _fetch_urllib(self, url):
+    def _fetch_urllib(self, url, chunk_size=65536):
         save_file = self.stage.save_filename
 
         request = urllib.request.Request(url, headers={"User-Agent": web_util.SPACK_USER_AGENT})
@@ -326,8 +438,15 @@ def _fetch_urllib(self, url):
         try:
             response = web_util.urlopen(request)
             tty.msg(f"Fetching {url}")
+            progress = FetchProgress.from_headers(response.headers, enabled=sys.stdout.isatty())
             with open(save_file, "wb") as f:
-                shutil.copyfileobj(response, f)
+                while True:
+                    chunk = response.read(chunk_size)
+                    if not chunk:
+                        break
+                    f.write(chunk)
+                    progress.advance(len(chunk))
+            progress.print(final=True)
         except OSError as e:
             # clean up archive on failure.
             if self.archive_file:
@@ -345,7 +464,7 @@ def _fetch_urllib(self, url):
         self._check_headers(str(response.headers))
 
     @_needs_stage
-    def _fetch_curl(self, url):
+    def _fetch_curl(self, url, config_args=[]):
         save_file = None
         partial_file = None
         if self.stage.save_filename:
@@ -374,7 +493,7 @@ def _fetch_curl(self, url):
             timeout = self.extra_options.get("timeout")
 
         base_args = web_util.base_curl_fetch_args(url, timeout)
-        curl_args = save_args + base_args + cookie_args
+        curl_args = config_args + save_args + base_args + cookie_args
 
         # Run curl but grab the mime type from the http headers
         curl = self.curl

lib/spack/spack/install_test.py

@@ -12,7 +12,7 @@
 import shutil
 import sys
 from collections import Counter, OrderedDict
-from typing import Callable, List, Optional, Tuple, Type, TypeVar, Union
+from typing import Callable, Iterable, List, Optional, Tuple, Type, TypeVar, Union
 
 import llnl.util.filesystem as fs
 import llnl.util.tty as tty
@@ -391,7 +391,7 @@ def phase_tests(self, builder, phase_name: str, method_names: List[str]):
             if self.test_failures:
                 raise TestFailure(self.test_failures)
 
-    def stand_alone_tests(self, kwargs):
+    def stand_alone_tests(self, kwargs, timeout: Optional[int] = None) -> None:
         """Run the package's stand-alone tests.
 
         Args:
@@ -399,7 +399,9 @@ def stand_alone_tests(self, kwargs):
         """
         import spack.build_environment  # avoid circular dependency
 
-        spack.build_environment.start_build_process(self.pkg, test_process, kwargs)
+        spack.build_environment.start_build_process(
+            self.pkg, test_process, kwargs, timeout=timeout
+        )
 
     def parts(self) -> int:
         """The total number of (checked) test parts."""
@@ -847,7 +849,7 @@ def write_test_summary(counts: "Counter"):
 class TestSuite:
     """The class that manages specs for ``spack test run`` execution."""
 
-    def __init__(self, specs, alias=None):
+    def __init__(self, specs: Iterable[Spec], alias: Optional[str] = None) -> None:
         # copy so that different test suites have different package objects
         # even if they contain the same spec
         self.specs = [spec.copy() for spec in specs]
@@ -855,42 +857,43 @@ def __init__(self, specs, alias=None):
         self.current_base_spec = None  # spec currently running do_test
 
         self.alias = alias
-        self._hash = None
-        self._stage = None
+        self._hash: Optional[str] = None
+        self._stage: Optional[Prefix] = None
 
         self.counts: "Counter" = Counter()
 
     @property
-    def name(self):
+    def name(self) -> str:
         """The name (alias or, if none, hash) of the test suite."""
         return self.alias if self.alias else self.content_hash
 
     @property
-    def content_hash(self):
+    def content_hash(self) -> str:
         """The hash used to uniquely identify the test suite."""
         if not self._hash:
             json_text = sjson.dump(self.to_dict())
+            assert json_text is not None, f"{__name__} unexpected value for 'json_text'"
             sha = hashlib.sha1(json_text.encode("utf-8"))
             b32_hash = base64.b32encode(sha.digest()).lower()
             b32_hash = b32_hash.decode("utf-8")
             self._hash = b32_hash
         return self._hash
 
-    def __call__(self, *args, **kwargs):
+    def __call__(
+        self,
+        *,
+        remove_directory: bool = True,
+        dirty: bool = False,
+        fail_first: bool = False,
+        externals: bool = False,
+        timeout: Optional[int] = None,
+    ):
         self.write_reproducibility_data()
-
-        remove_directory = kwargs.get("remove_directory", True)
-        dirty = kwargs.get("dirty", False)
-        fail_first = kwargs.get("fail_first", False)
-        externals = kwargs.get("externals", False)
-
         for spec in self.specs:
             try:
                 if spec.package.test_suite:
                     raise TestSuiteSpecError(
-                        "Package {} cannot be run in two test suites at once".format(
-                            spec.package.name
-                        )
+                        f"Package {spec.package.name} cannot be run in two test suites at once"
                     )
 
                 # Set up the test suite to know which test is running
@@ -905,7 +908,7 @@ def __call__(self, *args, **kwargs):
                 fs.mkdirp(test_dir)
 
                 # run the package tests
-                spec.package.do_test(dirty=dirty, externals=externals)
+                spec.package.do_test(dirty=dirty, externals=externals, timeout=timeout)
 
                 # Clean up on success
                 if remove_directory:
@@ -956,15 +959,12 @@ def __call__(self, *args, **kwargs):
         if failures:
             raise TestSuiteFailure(failures)
 
-    def test_status(self, spec: spack.spec.Spec, externals: bool) -> Optional[TestStatus]:
-        """Determine the overall test results status for the spec.
+    def test_status(self, spec: spack.spec.Spec, externals: bool) -> TestStatus:
+        """Returns the overall test results status for the spec.
 
         Args:
             spec: instance of the spec under test
             externals: ``True`` if externals are to be tested, else ``False``
-
-        Returns:
-            the spec's test status if available or ``None``
         """
         tests_status_file = self.tested_file_for_spec(spec)
         if not os.path.exists(tests_status_file):
@@ -981,109 +981,84 @@ def test_status(self, spec: spack.spec.Spec, externals: bool) -> Optional[TestSt
             value = (f.read()).strip("\n")
             return TestStatus(int(value)) if value else TestStatus.NO_TESTS
 
-    def ensure_stage(self):
+    def ensure_stage(self) -> None:
         """Ensure the test suite stage directory exists."""
         if not os.path.exists(self.stage):
             fs.mkdirp(self.stage)
 
     @property
-    def stage(self):
-        """The root test suite stage directory.
-
-        Returns:
-            str: the spec's test stage directory path
-        """
+    def stage(self) -> Prefix:
+        """The root test suite stage directory"""
         if not self._stage:
             self._stage = Prefix(fs.join_path(get_test_stage_dir(), self.content_hash))
         return self._stage
 
     @stage.setter
-    def stage(self, value):
+    def stage(self, value: Union[Prefix, str]) -> None:
         """Set the value of a non-default stage directory."""
         self._stage = value if isinstance(value, Prefix) else Prefix(value)
 
     @property
-    def results_file(self):
+    def results_file(self) -> Prefix:
         """The path to the results summary file."""
         return self.stage.join(results_filename)
 
     @classmethod
-    def test_pkg_id(cls, spec):
+    def test_pkg_id(cls, spec: Spec) -> str:
         """The standard install test package identifier.
 
         Args:
             spec: instance of the spec under test
-
-        Returns:
-            str: the install test package identifier
         """
         return spec.format_path("{name}-{version}-{hash:7}")
 
     @classmethod
-    def test_log_name(cls, spec):
+    def test_log_name(cls, spec: Spec) -> str:
         """The standard log filename for a spec.
 
         Args:
-            spec (spack.spec.Spec): instance of the spec under test
-
-        Returns:
-            str: the spec's log filename
+            spec: instance of the spec under test
         """
-        return "%s-test-out.txt" % cls.test_pkg_id(spec)
+        return f"{cls.test_pkg_id(spec)}-test-out.txt"
 
-    def log_file_for_spec(self, spec):
+    def log_file_for_spec(self, spec: Spec) -> Prefix:
         """The test log file path for the provided spec.
 
         Args:
-            spec (spack.spec.Spec): instance of the spec under test
-
-        Returns:
-            str: the path to the spec's log file
+            spec: instance of the spec under test
         """
         return self.stage.join(self.test_log_name(spec))
 
-    def test_dir_for_spec(self, spec):
+    def test_dir_for_spec(self, spec: Spec) -> Prefix:
         """The path to the test stage directory for the provided spec.
 
         Args:
-            spec (spack.spec.Spec): instance of the spec under test
-
-        Returns:
-            str: the spec's test stage directory path
+            spec: instance of the spec under test
         """
         return Prefix(self.stage.join(self.test_pkg_id(spec)))
 
     @classmethod
-    def tested_file_name(cls, spec):
+    def tested_file_name(cls, spec: Spec) -> str:
         """The standard test status filename for the spec.
 
         Args:
-            spec (spack.spec.Spec): instance of the spec under test
-
-        Returns:
-            str: the spec's test status filename
+            spec: instance of the spec under test
         """
         return "%s-tested.txt" % cls.test_pkg_id(spec)
 
-    def tested_file_for_spec(self, spec):
+    def tested_file_for_spec(self, spec: Spec) -> str:
         """The test status file path for the spec.
 
         Args:
-            spec (spack.spec.Spec): instance of the spec under test
-
-        Returns:
-            str: the spec's test status file path
+            spec: instance of the spec under test
         """
         return fs.join_path(self.stage, self.tested_file_name(spec))
 
     @property
-    def current_test_cache_dir(self):
+    def current_test_cache_dir(self) -> str:
         """Path to the test stage directory where the current spec's cached
         build-time files were automatically copied.
 
-        Returns:
-            str: path to the current spec's staged, cached build-time files.
-
         Raises:
             TestSuiteSpecError: If there is no spec being tested
         """
@@ -1095,13 +1070,10 @@ def current_test_cache_dir(self):
         return self.test_dir_for_spec(base_spec).cache.join(test_spec.name)
 
     @property
-    def current_test_data_dir(self):
+    def current_test_data_dir(self) -> str:
         """Path to the test stage directory where the current spec's custom
         package (data) files were automatically copied.
 
-        Returns:
-            str: path to the current spec's staged, custom package (data) files
-
         Raises:
             TestSuiteSpecError: If there is no spec being tested
         """
@@ -1112,17 +1084,17 @@ def current_test_data_dir(self):
         base_spec = self.current_base_spec
         return self.test_dir_for_spec(base_spec).data.join(test_spec.name)
 
-    def write_test_result(self, spec, result):
+    def write_test_result(self, spec: Spec, result: TestStatus) -> None:
         """Write the spec's test result to the test suite results file.
 
         Args:
-            spec (spack.spec.Spec): instance of the spec under test
-            result (str): result from the spec's test execution (e.g, PASSED)
+            spec: instance of the spec under test
+            result: result from the spec's test execution (e.g, PASSED)
         """
         msg = f"{self.test_pkg_id(spec)} {result}"
         _add_msg_to_file(self.results_file, msg)
 
-    def write_reproducibility_data(self):
+    def write_reproducibility_data(self) -> None:
         for spec in self.specs:
             repo_cache_path = self.stage.repo.join(spec.name)
             spack.repo.PATH.dump_provenance(spec, repo_cache_path)
@@ -1167,12 +1139,12 @@ def from_dict(d):
         return TestSuite(specs, alias)
 
     @staticmethod
-    def from_file(filename):
+    def from_file(filename: str) -> "TestSuite":
         """Instantiate a TestSuite using the specs and optional alias
         provided in the given file.
 
         Args:
-            filename (str): The path to the JSON file containing the test
+            filename: The path to the JSON file containing the test
                 suite specs and optional alias.
 
         Raises:

lib/spack/spack/installer.py

@@ -566,10 +566,11 @@ def dump_packages(spec: "spack.spec.Spec", path: str) -> None:
                 tty.warn(f"Warning: Couldn't copy in provenance for {node.name}")
 
         # Create a destination repository
-        dest_repo_root = os.path.join(path, node.namespace)
-        if not os.path.exists(dest_repo_root):
-            spack.repo.create_repo(dest_repo_root)
-        repo = spack.repo.from_path(dest_repo_root)
+        pkg_api = spack.repo.PATH.get_repo(node.namespace).package_api
+        repo_root = os.path.join(path, node.namespace) if pkg_api < (2, 0) else path
+        repo = spack.repo.create_or_construct(
+            repo_root, namespace=node.namespace, package_api=pkg_api
+        )
 
         # Get the location of the package in the dest repo.
         dest_pkg_dir = repo.dirname_for_package_name(node.name)

lib/spack/spack/main.py

@@ -20,6 +20,7 @@
 import signal
 import subprocess as sp
 import sys
+import tempfile
 import traceback
 import warnings
 from typing import List, Tuple
@@ -41,6 +42,7 @@
 import spack.paths
 import spack.platforms
 import spack.repo
+import spack.solver.asp
 import spack.spec
 import spack.store
 import spack.util.debug
@@ -871,8 +873,8 @@ def add_command_line_scopes(
     """
     for i, path in enumerate(command_line_scopes):
         name = f"cmd_scope_{i}"
-        scopes = ev.environment_path_scopes(name, path)
-        if scopes is None:
+        scope = ev.environment_path_scope(name, path)
+        if scope is None:
             if os.path.isdir(path):  # directory with config files
                 cfg.push_scope(
                     spack.config.DirectoryConfigScope(name, path, writable=False),
@@ -885,8 +887,7 @@ def add_command_line_scopes(
             else:
                 raise spack.error.ConfigError(f"Invalid configuration scope: {path}")
 
-        for scope in scopes:
-            cfg.push_scope(scope, priority=ConfigScopePriority.CUSTOM)
+        cfg.push_scope(scope, priority=ConfigScopePriority.CUSTOM)
 
 
 def _main(argv=None):
@@ -1047,6 +1048,10 @@ def main(argv=None):
     try:
         return _main(argv)
 
+    except spack.solver.asp.OutputDoesNotSatisfyInputError as e:
+        _handle_solver_bug(e)
+        return 1
+
     except spack.error.SpackError as e:
         tty.debug(e)
         e.die()  # gracefully die on any SpackErrors
@@ -1070,5 +1075,45 @@ def main(argv=None):
         return 3
 
 
+def _handle_solver_bug(
+    e: spack.solver.asp.OutputDoesNotSatisfyInputError, out=sys.stderr, root=None
+) -> None:
+    # when the solver outputs specs that do not satisfy the input and spack is used as a command
+    # line tool, we dump the incorrect output specs to json so users can upload them in bug reports
+    wrong_output = [(input, output) for input, output in e.input_to_output if output is not None]
+    no_output = [input for input, output in e.input_to_output if output is None]
+    if no_output:
+        tty.error(
+            "internal solver error: the following specs were not solved:\n    - "
+            + "\n    - ".join(str(s) for s in no_output),
+            stream=out,
+        )
+    if wrong_output:
+        msg = (
+            "internal solver error: the following specs were concretized, but do not satisfy the "
+            "input:\n    - "
+            + "\n    - ".join(str(s) for s, _ in wrong_output)
+            + "\n    Please report a bug at https://github.com/spack/spack/issues"
+        )
+        # try to write the input/output specs to a temporary directory for bug reports
+        try:
+            tmpdir = tempfile.mkdtemp(prefix="spack-asp-", dir=root)
+            files = []
+            for i, (input, output) in enumerate(wrong_output, start=1):
+                in_file = os.path.join(tmpdir, f"input-{i}.json")
+                out_file = os.path.join(tmpdir, f"output-{i}.json")
+                files.append(in_file)
+                files.append(out_file)
+                with open(in_file, "w", encoding="utf-8") as f:
+                    input.to_json(f)
+                with open(out_file, "w", encoding="utf-8") as f:
+                    output.to_json(f)
+
+            msg += " and attach the following files:\n    - " + "\n    - ".join(files)
+        except Exception:
+            msg += "."
+        tty.error(msg, stream=out)
+
+
 class SpackCommandError(Exception):
     """Raised when SpackCommand execution fails."""

lib/spack/spack/package.py

@@ -162,6 +162,7 @@ class tty:
 configure: Executable
 make_jobs: int
 make: MakeExecutable
+nmake: Executable
 ninja: MakeExecutable
 python_include: str
 python_platlib: str

lib/spack/spack/package_base.py

@@ -14,7 +14,6 @@
 import functools
 import glob
 import hashlib
-import importlib
 import io
 import os
 import re
@@ -28,7 +27,7 @@
 
 import llnl.util.filesystem as fsys
 import llnl.util.tty as tty
-from llnl.util.lang import classproperty, memoized
+from llnl.util.lang import ClassProperty, classproperty, memoized
 
 import spack.config
 import spack.dependency
@@ -48,6 +47,7 @@
 import spack.url
 import spack.util.environment
 import spack.util.executable
+import spack.util.naming
 import spack.util.path
 import spack.util.web
 import spack.variant
@@ -701,10 +701,10 @@ class PackageBase(WindowsRPath, PackageViewMixin, metaclass=PackageMeta):
     _verbose = None
 
     #: Package homepage where users can find more information about the package
-    homepage: Optional[str] = None
+    homepage: ClassProperty[Optional[str]] = None
 
     #: Default list URL (place to find available versions)
-    list_url: Optional[str] = None
+    list_url: ClassProperty[Optional[str]] = None
 
     #: Link depth to which list_url should be searched for new versions
     list_depth = 0
@@ -818,12 +818,12 @@ def package_dir(cls):
 
     @classproperty
     def module(cls):
-        """Module object (not just the name) that this package is defined in.
+        """Module instance that this package class is defined in.
 
         We use this to add variables to package modules.  This makes
         install() methods easier to write (e.g., can call configure())
         """
-        return importlib.import_module(cls.__module__)
+        return sys.modules[cls.__module__]
 
     @classproperty
     def namespace(cls):
@@ -839,26 +839,36 @@ def fullname(cls):
     def fullnames(cls):
         """Fullnames for this package and any packages from which it inherits."""
         fullnames = []
-        for cls in cls.__mro__:
-            namespace = getattr(cls, "namespace", None)
-            if namespace:
-                fullnames.append("%s.%s" % (namespace, cls.name))
-            if namespace == "builtin":
-                # builtin packages cannot inherit from other repos
+        for base in cls.__mro__:
+            if not spack.repo.is_package_module(base.__module__):
                 break
+            fullnames.append(base.fullname)
         return fullnames
 
     @classproperty
     def name(cls):
-        """The name of this package.
-
-        The name of a package is the name of its Python module, without
-        the containing module names.
-        """
+        """The name of this package."""
         if cls._name is None:
-            cls._name = cls.module.__name__
-            if "." in cls._name:
-                cls._name = cls._name[cls._name.rindex(".") + 1 :]
+            # We cannot know the exact package API version, but we can distinguish between v1
+            # v2 based on the module. We don't want to figure out the exact package API version
+            # since it requires parsing the repo.yaml.
+            module = cls.__module__
+
+            if module.startswith(spack.repo.PKG_MODULE_PREFIX_V1):
+                version = (1, 0)
+            elif module.startswith(spack.repo.PKG_MODULE_PREFIX_V2):
+                version = (2, 0)
+            else:
+                raise ValueError(f"Package {cls.__qualname__} is not a known Spack package")
+
+            if version < (2, 0):
+                # spack.pkg.builtin.package_name.
+                _, _, pkg_module = module.rpartition(".")
+            else:
+                # spack_repo.builtin.packages.package_name.package
+                pkg_module = module.rsplit(".", 2)[-2]
+
+            cls._name = spack.util.naming.pkg_dir_to_pkg_name(pkg_module, version)
         return cls._name
 
     @classproperty
@@ -1821,7 +1831,7 @@ def _resource_stage(self, resource):
         resource_stage_folder = "-".join(pieces)
         return resource_stage_folder
 
-    def do_test(self, dirty=False, externals=False):
+    def do_test(self, *, dirty=False, externals=False, timeout: Optional[int] = None):
         if self.test_requires_compiler and not any(
             lang in self.spec for lang in ("c", "cxx", "fortran")
         ):
@@ -1839,7 +1849,7 @@ def do_test(self, dirty=False, externals=False):
             "verbose": tty.is_verbose(),
         }
 
-        self.tester.stand_alone_tests(kwargs)
+        self.tester.stand_alone_tests(kwargs, timeout=timeout)
 
     def unit_test_check(self):
         """Hook for unit tests to assert things about package internals.

lib/spack/spack/paths.py

@@ -56,8 +56,9 @@
 
 # read-only things in $spack/var/spack
 repos_path = os.path.join(var_path, "repos")
-packages_path = os.path.join(repos_path, "builtin")
-mock_packages_path = os.path.join(repos_path, "builtin.mock")
+test_repos_path = os.path.join(var_path, "test_repos")
+packages_path = os.path.join(repos_path, "spack_repo", "builtin")
+mock_packages_path = os.path.join(test_repos_path, "builtin.mock")
 
 #
 # Writable things in $spack/var/spack

lib/spack/spack/repo.py

@@ -47,40 +47,34 @@
 import spack.util.path
 import spack.util.spack_yaml as syaml
 
-#: Package modules are imported as spack.pkg.<repo-namespace>.<pkg-name>
-ROOT_PYTHON_NAMESPACE = "spack.pkg"
+PKG_MODULE_PREFIX_V1 = "spack.pkg."
+PKG_MODULE_PREFIX_V2 = "spack_repo."
 
 _API_REGEX = re.compile(r"^v(\d+)\.(\d+)$")
 
 
-def python_package_for_repo(namespace):
-    """Returns the full namespace of a repository, given its relative one
-
-    For instance:
-
-        python_package_for_repo('builtin') == 'spack.pkg.builtin'
-
-    Args:
-        namespace (str): repo namespace
-    """
-    return "{0}.{1}".format(ROOT_PYTHON_NAMESPACE, namespace)
+def is_package_module(fullname: str) -> bool:
+    """Check if the given module is a package module."""
+    return fullname.startswith(PKG_MODULE_PREFIX_V1) or fullname.startswith(PKG_MODULE_PREFIX_V2)
 
 
-def namespace_from_fullname(fullname):
+def namespace_from_fullname(fullname: str) -> str:
     """Return the repository namespace only for the full module name.
 
     For instance:
 
-        namespace_from_fullname('spack.pkg.builtin.hdf5') == 'builtin'
+        namespace_from_fullname("spack.pkg.builtin.hdf5") == "builtin"
+        namespace_from_fullname("spack_repo.x.y.z.packages.pkg_name.package") == "x.y.z"
 
     Args:
-        fullname (str): full name for the Python module
+        fullname: full name for the Python module
     """
-    namespace, dot, module = fullname.rpartition(".")
-    prefix_and_dot = "{0}.".format(ROOT_PYTHON_NAMESPACE)
-    if namespace.startswith(prefix_and_dot):
-        namespace = namespace[len(prefix_and_dot) :]
-    return namespace
+    if fullname.startswith(PKG_MODULE_PREFIX_V1):
+        namespace, _, _ = fullname.rpartition(".")
+        return namespace[len(PKG_MODULE_PREFIX_V1) :]
+    elif fullname.startswith(PKG_MODULE_PREFIX_V2) and fullname.endswith(".package"):
+        return ".".join(fullname.split(".")[1:-3])
+    return fullname
 
 
 class SpackNamespaceLoader:
@@ -92,14 +86,14 @@ def exec_module(self, module):
 
 
 class ReposFinder:
-    """MetaPathFinder class that loads a Python module corresponding to a Spack package.
+    """MetaPathFinder class that loads a Python module corresponding to an API v1 Spack package.
 
     Returns a loader based on the inspection of the current repository list.
     """
 
     def __init__(self):
         self._repo_init = _path
-        self._repo = None
+        self._repo: Optional[RepoType] = None
 
     @property
     def current_repository(self):
@@ -127,7 +121,7 @@ def find_spec(self, fullname, python_path, target=None):
             raise RuntimeError('cannot reload module "{0}"'.format(fullname))
 
         # Preferred API from https://peps.python.org/pep-0451/
-        if not fullname.startswith(ROOT_PYTHON_NAMESPACE):
+        if not fullname.startswith(PKG_MODULE_PREFIX_V1) and fullname != "spack.pkg":
             return None
 
         loader = self.compute_loader(fullname)
@@ -135,16 +129,17 @@ def find_spec(self, fullname, python_path, target=None):
             return None
         return importlib.util.spec_from_loader(fullname, loader)
 
-    def compute_loader(self, fullname):
+    def compute_loader(self, fullname: str):
         # namespaces are added to repo, and package modules are leaves.
         namespace, dot, module_name = fullname.rpartition(".")
 
         # If it's a module in some repo, or if it is the repo's namespace, let the repo handle it.
-        is_repo_path = isinstance(self.current_repository, RepoPath)
+        current_repo = self.current_repository
+        is_repo_path = isinstance(current_repo, RepoPath)
         if is_repo_path:
-            repos = self.current_repository.repos
+            repos = current_repo.repos
         else:
-            repos = [self.current_repository]
+            repos = [current_repo]
 
         for repo in repos:
             # We are using the namespace of the repo and the repo contains the package
@@ -161,7 +156,9 @@ def compute_loader(self, fullname):
 
         # No repo provides the namespace, but it is a valid prefix of
         # something in the RepoPath.
-        if is_repo_path and self.current_repository.by_namespace.is_prefix(fullname):
+        if is_repo_path and current_repo.by_namespace.is_prefix(
+            fullname[len(PKG_MODULE_PREFIX_V1) :]
+        ):
             return SpackNamespaceLoader()
 
         return None
@@ -179,12 +176,12 @@ def compute_loader(self, fullname):
 NOT_PROVIDED = object()
 
 
-def packages_path():
+def builtin_repo() -> "Repo":
     """Get the test repo if it is active, otherwise the builtin repo."""
     try:
-        return PATH.get_repo("builtin.mock").packages_path
+        return PATH.get_repo("builtin.mock")
     except UnknownNamespaceError:
-        return PATH.get_repo("builtin").packages_path
+        return PATH.get_repo("builtin")
 
 
 class GitExe:
@@ -192,24 +189,25 @@ class GitExe:
     # invocations.
     #
     # Not using -C as that is not supported for git < 1.8.5.
-    def __init__(self):
+    def __init__(self, packages_path: str):
         self._git_cmd = spack.util.git.git(required=True)
+        self.packages_dir = packages_path
 
-    def __call__(self, *args, **kwargs):
-        with working_dir(packages_path()):
-            return self._git_cmd(*args, **kwargs)
+    def __call__(self, *args, **kwargs) -> str:
+        with working_dir(self.packages_dir):
+            return self._git_cmd(*args, **kwargs, output=str)
 
 
-def list_packages(rev):
+def list_packages(rev: str, repo: "Repo") -> List[str]:
     """List all packages associated with the given revision"""
-    git = GitExe()
+    git = GitExe(repo.packages_path)
 
     # git ls-tree does not support ... merge-base syntax, so do it manually
     if rev.endswith("..."):
         ref = rev.replace("...", "")
-        rev = git("merge-base", ref, "HEAD", output=str).strip()
+        rev = git("merge-base", ref, "HEAD").strip()
 
-    output = git("ls-tree", "-r", "--name-only", rev, output=str)
+    output = git("ls-tree", "-r", "--name-only", rev)
 
     # recursively list the packages directory
     package_paths = [
@@ -217,54 +215,54 @@ def list_packages(rev):
     ]
 
     # take the directory names with one-level-deep package files
-    package_names = sorted(set([line[0] for line in package_paths if len(line) == 2]))
+    package_names = [
+        nm.pkg_dir_to_pkg_name(line[0], repo.package_api)
+        for line in package_paths
+        if len(line) == 2
+    ]
 
-    return package_names
+    return sorted(set(package_names))
 
 
-def diff_packages(rev1, rev2):
+def diff_packages(rev1: str, rev2: str, repo: "Repo") -> Tuple[Set[str], Set[str]]:
     """Compute packages lists for the two revisions and return a tuple
     containing all the packages in rev1 but not in rev2 and all the
     packages in rev2 but not in rev1."""
-    p1 = set(list_packages(rev1))
-    p2 = set(list_packages(rev2))
+    p1 = set(list_packages(rev1, repo))
+    p2 = set(list_packages(rev2, repo))
     return p1.difference(p2), p2.difference(p1)
 
 
-def get_all_package_diffs(type, rev1="HEAD^1", rev2="HEAD"):
-    """Show packages changed, added, or removed (or any combination of those)
-       since a commit.
+def get_all_package_diffs(type: str, repo: "Repo", rev1="HEAD^1", rev2="HEAD") -> Set[str]:
+    """Get packages changed, added, or removed (or any combination of those) since a commit.
 
     Arguments:
 
-        type (str): String containing one or more of 'A', 'R', 'C'
-        rev1 (str): Revision to compare against, default is 'HEAD^'
-        rev2 (str): Revision to compare to rev1, default is 'HEAD'
-
-    Returns:
-
-        A set contain names of affected packages.
+        type: String containing one or more of 'A', 'R', 'C'
+        rev1: Revision to compare against, default is 'HEAD^'
+        rev2: Revision to compare to rev1, default is 'HEAD'
     """
     lower_type = type.lower()
     if not re.match("^[arc]*$", lower_type):
         tty.die(
-            "Invald change type: '%s'." % type,
-            "Can contain only A (added), R (removed), or C (changed)",
+            f"Invalid change type: '{type}'. "
+            "Can contain only A (added), R (removed), or C (changed)"
         )
 
-    removed, added = diff_packages(rev1, rev2)
+    removed, added = diff_packages(rev1, rev2, repo)
 
-    git = GitExe()
-    out = git("diff", "--relative", "--name-only", rev1, rev2, output=str).strip()
+    git = GitExe(repo.packages_path)
+    out = git("diff", "--relative", "--name-only", rev1, rev2).strip()
 
     lines = [] if not out else re.split(r"\s+", out)
-    changed = set()
+    changed: Set[str] = set()
     for path in lines:
-        pkg_name, _, _ = path.partition("/")
+        dir_name, _, _ = path.partition("/")
+        pkg_name = nm.pkg_dir_to_pkg_name(dir_name, repo.package_api)
         if pkg_name not in added and pkg_name not in removed:
             changed.add(pkg_name)
 
-    packages = set()
+    packages: Set[str] = set()
     if "a" in lower_type:
         packages |= added
     if "r" in lower_type:
@@ -275,14 +273,14 @@ def get_all_package_diffs(type, rev1="HEAD^1", rev2="HEAD"):
     return packages
 
 
-def add_package_to_git_stage(packages):
+def add_package_to_git_stage(packages: List[str], repo: "Repo") -> None:
     """add a package to the git stage with `git add`"""
-    git = GitExe()
+    git = GitExe(repo.packages_path)
 
     for pkg_name in packages:
         filename = PATH.filename_for_package_name(pkg_name)
         if not os.path.isfile(filename):
-            tty.die("No such package: %s.  Path does not exist:" % pkg_name, filename)
+            tty.die(f"No such package: {pkg_name}.  Path does not exist:", filename)
 
         git("add", filename)
 
@@ -352,9 +350,10 @@ class FastPackageChecker(collections.abc.Mapping):
     #: Global cache, reused by every instance
     _paths_cache: Dict[str, Dict[str, os.stat_result]] = {}
 
-    def __init__(self, packages_path):
+    def __init__(self, packages_path: str, package_api: Tuple[int, int]):
         # The path of the repository managed by this instance
         self.packages_path = packages_path
+        self.package_api = package_api
 
         # If the cache we need is not there yet, then build it appropriately
         if packages_path not in self._paths_cache:
@@ -379,41 +378,38 @@ def _create_new_cache(self) -> Dict[str, os.stat_result]:
         # Create a dictionary that will store the mapping between a
         # package name and its stat info
         cache: Dict[str, os.stat_result] = {}
-        for pkg_name in os.listdir(self.packages_path):
-            # Skip non-directories in the package root.
-            pkg_dir = os.path.join(self.packages_path, pkg_name)
+        with os.scandir(self.packages_path) as entries:
+            for entry in entries:
+                # Construct the file name from the directory
+                pkg_file = os.path.join(entry.path, package_file_name)
 
-            # Warn about invalid names that look like packages.
-            if not nm.valid_module_name(pkg_name):
-                if not pkg_name.startswith(".") and pkg_name != "repo.yaml":
+                try:
+                    sinfo = os.stat(pkg_file)
+                except OSError as e:
+                    if e.errno in (errno.ENOENT, errno.ENOTDIR):
+                        # No package.py file here.
+                        continue
+                    elif e.errno == errno.EACCES:
+                        tty.warn(f"Can't read package file {pkg_file}.")
+                        continue
+                    raise e
+
+                # If it's not a file, skip it.
+                if not stat.S_ISREG(sinfo.st_mode):
+                    continue
+
+                # Only consider package.py files in directories that are valid module names under
+                # the current package API
+                if not nm.valid_module_name(entry.name, self.package_api):
+                    x, y = self.package_api
                     tty.warn(
-                        'Skipping package at {0}. "{1}" is not '
-                        "a valid Spack module name.".format(pkg_dir, pkg_name)
+                        f"Package {pkg_file} cannot be used because `{entry.name}` is not a valid "
+                        f"Spack package module name for Package API v{x}.{y}."
                     )
-                continue
-
-            # Construct the file name from the directory
-            pkg_file = os.path.join(self.packages_path, pkg_name, package_file_name)
-
-            # Use stat here to avoid lots of calls to the filesystem.
-            try:
-                sinfo = os.stat(pkg_file)
-            except OSError as e:
-                if e.errno == errno.ENOENT:
-                    # No package.py file here.
                     continue
-                elif e.errno == errno.EACCES:
-                    tty.warn("Can't read package file %s." % pkg_file)
-                    continue
-                raise e
 
-            # If it's not a file, skip it.
-            if stat.S_ISDIR(sinfo.st_mode):
-                continue
-
-            # If it is a file, then save the stats under the
-            # appropriate key
-            cache[pkg_name] = sinfo
+                # Store the stat info by package name.
+                cache[nm.pkg_dir_to_pkg_name(entry.name, self.package_api)] = sinfo
 
         return cache
 
@@ -688,7 +684,7 @@ def put_first(self, repo: "Repo") -> None:
             return
 
         self.repos.insert(0, repo)
-        self.by_namespace[repo.full_namespace] = repo
+        self.by_namespace[repo.namespace] = repo
 
     def put_last(self, repo):
         """Add repo last in the search path."""
@@ -700,8 +696,8 @@ def put_last(self, repo):
         self.repos.append(repo)
 
         # don't mask any higher-precedence repos with same namespace
-        if repo.full_namespace not in self.by_namespace:
-            self.by_namespace[repo.full_namespace] = repo
+        if repo.namespace not in self.by_namespace:
+            self.by_namespace[repo.namespace] = repo
 
     def remove(self, repo):
         """Remove a repo from the search path."""
@@ -710,10 +706,9 @@ def remove(self, repo):
 
     def get_repo(self, namespace: str) -> "Repo":
         """Get a repository by namespace."""
-        full_namespace = python_package_for_repo(namespace)
-        if full_namespace not in self.by_namespace:
+        if namespace not in self.by_namespace:
             raise UnknownNamespaceError(namespace)
-        return self.by_namespace[full_namespace]
+        return self.by_namespace[namespace]
 
     def first_repo(self) -> Optional["Repo"]:
         """Get the first repo in precedence order."""
@@ -821,10 +816,9 @@ def repo_for_pkg(self, spec: Union[str, "spack.spec.Spec"]) -> "Repo":
         # If the spec already has a namespace, then return the
         # corresponding repo if we know about it.
         if namespace:
-            fullspace = python_package_for_repo(namespace)
-            if fullspace not in self.by_namespace:
+            if namespace not in self.by_namespace:
                 raise UnknownNamespaceError(namespace, name=name)
-            return self.by_namespace[fullspace]
+            return self.by_namespace[namespace]
 
         # If there's no namespace, search in the RepoPath.
         for repo in self.repos:
@@ -845,8 +839,15 @@ def get(self, spec: "spack.spec.Spec") -> "spack.package_base.PackageBase":
         assert isinstance(spec, spack.spec.Spec) and spec.concrete, msg
         return self.repo_for_pkg(spec).get(spec)
 
+    def python_paths(self) -> List[str]:
+        """Return a list of all the Python paths in the repos."""
+        return [repo.python_path for repo in self.repos if repo.python_path]
+
     def get_pkg_class(self, pkg_name: str) -> Type["spack.package_base.PackageBase"]:
         """Find a class for the spec's package and return the class object."""
+        for p in self.python_paths():
+            if p not in sys.path:
+                sys.path.insert(0, p)
         return self.repo_for_pkg(pkg_name).get_pkg_class(pkg_name)
 
     @autospec
@@ -942,6 +943,30 @@ def _parse_package_api_version(
     )
 
 
+def _validate_and_normalize_subdir(subdir: Any, root: str, package_api: Tuple[int, int]) -> str:
+    if not isinstance(subdir, str):
+        raise BadRepoError(f"Invalid subdirectory '{subdir}' in '{root}'. Must be a string")
+
+    if package_api < (2, 0):
+        return subdir  # In v1.x we did not validate subdir names
+
+    if subdir in (".", ""):
+        raise BadRepoError(
+            f"Invalid subdirectory '{subdir}' in '{root}'. Use a symlink packages -> . instead"
+        )
+
+    # Otherwise we expect a directory name (not path) that can be used as a Python module.
+    if os.sep in subdir:
+        raise BadRepoError(
+            f"Invalid subdirectory '{subdir}' in '{root}'. Expected a directory name, not a path"
+        )
+    if not nm.valid_module_name(subdir, package_api):
+        raise BadRepoError(
+            f"Invalid subdirectory '{subdir}' in '{root}'. Must be a valid Python module name"
+        )
+    return subdir
+
+
 class Repo:
     """Class representing a package repository in the filesystem.
 
@@ -962,6 +987,8 @@ class Repo:
         :py:data:`spack.package_api_version`.
     """
 
+    namespace: str
+
     def __init__(
         self,
         root: str,
@@ -991,32 +1018,79 @@ def check(condition, msg):
 
         # Read configuration and validate namespace
         config = self._read_config()
+
+        self.package_api = _parse_package_api_version(config)
+        self.subdirectory = _validate_and_normalize_subdir(
+            config.get("subdirectory", packages_dir_name), root, self.package_api
+        )
+        self.packages_path = os.path.join(self.root, self.subdirectory)
+
         check(
-            "namespace" in config,
-            f"{os.path.join(root, repo_config_name)} must define a namespace.",
+            os.path.isdir(self.packages_path),
+            f"No directory '{self.subdirectory}' found in '{root}'",
         )
 
-        self.namespace: str = config["namespace"]
-        check(
-            re.match(r"[a-zA-Z][a-zA-Z0-9_.]+", self.namespace),
-            f"Invalid namespace '{self.namespace}' in repo '{self.root}'. "
-            "Namespaces must be valid python identifiers separated by '.'",
-        )
+        # The parent dir of spack_repo/ which should be added to sys.path for api v2.x
+        self.python_path: Optional[str] = None
+
+        if self.package_api < (2, 0):
+            check(
+                "namespace" in config,
+                f"{os.path.join(root, repo_config_name)} must define a namespace.",
+            )
+            self.namespace = config["namespace"]
+            # Note: for Package API v1.x the namespace validation always had bugs, which won't be
+            # fixed for compatibility reasons. The regex is missing "$" at the end, and it claims
+            # to test for valid identifiers, but fails to split on `.` first.
+            check(
+                isinstance(self.namespace, str)
+                and re.match(r"[a-zA-Z][a-zA-Z0-9_.]+", self.namespace),
+                f"Invalid namespace '{self.namespace}' in repo '{self.root}'. "
+                "Namespaces must be valid python identifiers separated by '.'",
+            )
+        else:
+            # From Package API v2.0 the namespace follows from the directory structure.
+            check(
+                f"{os.sep}spack_repo{os.sep}" in self.root,
+                f"Invalid repository path '{self.root}'. "
+                f"Path must contain 'spack_repo{os.sep}'",
+            )
+            derived_namespace = self.root.rpartition(f"spack_repo{os.sep}")[2].replace(os.sep, ".")
+            if "namespace" in config:
+                self.namespace = config["namespace"]
+
+                check(
+                    isinstance(self.namespace, str) and self.namespace == derived_namespace,
+                    f"Namespace '{self.namespace}' should be {derived_namespace} or omitted in "
+                    f"{os.path.join(root, repo_config_name)}",
+                )
+            else:
+                self.namespace = derived_namespace
+
+            # strip the namespace directories from the root path to get the python path
+            # e.g. /my/pythonpath/spack_repo/x/y/z -> /my/pythonpath
+            python_path = self.root
+            for _ in self.namespace.split("."):
+                python_path = os.path.dirname(python_path)
+            self.python_path = os.path.dirname(python_path)
+
+            # check that all subdirectories are valid module names
+            check(
+                all(nm.valid_module_name(x, self.package_api) for x in self.namespace.split(".")),
+                f"Invalid namespace '{self.namespace}' in repo '{self.root}'",
+            )
 
         # Set up 'full_namespace' to include the super-namespace
-        self.full_namespace = python_package_for_repo(self.namespace)
+        if self.package_api < (2, 0):
+            self.full_namespace = f"{PKG_MODULE_PREFIX_V1}{self.namespace}"
+        elif self.subdirectory == ".":
+            self.full_namespace = f"{PKG_MODULE_PREFIX_V2}{self.namespace}"
+        else:
+            self.full_namespace = f"{PKG_MODULE_PREFIX_V2}{self.namespace}.{self.subdirectory}"
 
         # Keep name components around for checking prefixes.
         self._names = self.full_namespace.split(".")
 
-        packages_dir: str = config.get("subdirectory", packages_dir_name)
-        self.packages_path = os.path.join(self.root, packages_dir)
-        check(
-            os.path.isdir(self.packages_path), f"No directory '{packages_dir}' found in '{root}'"
-        )
-
-        self.package_api = _parse_package_api_version(config)
-
         # Class attribute overrides by package name
         self.overrides = overrides or {}
 
@@ -1030,27 +1104,36 @@ def check(condition, msg):
         self._repo_index: Optional[RepoIndex] = None
         self._cache = cache
 
+    @property
+    def package_api_str(self) -> str:
+        return f"v{self.package_api[0]}.{self.package_api[1]}"
+
     def finder(self, value: RepoPath) -> None:
         self._finder = value
 
     def real_name(self, import_name: str) -> Optional[str]:
         """Allow users to import Spack packages using Python identifiers.
 
-        A python identifier might map to many different Spack package
-        names due to hyphen/underscore ambiguity.
+        In Package API v1.x, there was no canonical module name for a package, and package's dir
+        was not necessarily a valid Python module name. For that case we have to guess the actual
+        package directory. From Package API v2.0 there is a one-to-one mapping between Spack
+        package names and Python module names, so there is no guessing.
 
-        Easy example:
-            num3proxy   -> 3proxy
-
-        Ambiguous:
+        For Packge API v1.x we support the following one-to-many mappings:
+            num3proxy -> 3proxy
             foo_bar -> foo_bar, foo-bar
-
-        More ambiguous:
             foo_bar_baz -> foo_bar_baz, foo-bar-baz, foo_bar-baz, foo-bar_baz
         """
+        if self.package_api >= (2, 0):
+            if nm.pkg_dir_to_pkg_name(import_name, package_api=self.package_api) in self:
+                return import_name
+            return None
+
         if import_name in self:
             return import_name
 
+        # For v1 generate the possible package names from a module name, and return the first
+        # package name that exists in this repo.
         options = nm.possible_spack_module_names(import_name)
         try:
             options.remove(import_name)
@@ -1183,7 +1266,9 @@ def extensions_for(
     def dirname_for_package_name(self, pkg_name: str) -> str:
         """Given a package name, get the directory containing its package.py file."""
         _, unqualified_name = self.partition_package_name(pkg_name)
-        return os.path.join(self.packages_path, unqualified_name)
+        return os.path.join(
+            self.packages_path, nm.pkg_name_to_pkg_dir(unqualified_name, self.package_api)
+        )
 
     def filename_for_package_name(self, pkg_name: str) -> str:
         """Get the filename for the module we should load for a particular
@@ -1200,7 +1285,7 @@ def filename_for_package_name(self, pkg_name: str) -> str:
     @property
     def _pkg_checker(self) -> FastPackageChecker:
         if self._fast_package_checker is None:
-            self._fast_package_checker = FastPackageChecker(self.packages_path)
+            self._fast_package_checker = FastPackageChecker(self.packages_path, self.package_api)
         return self._fast_package_checker
 
     def all_package_names(self, include_virtuals: bool = False) -> List[str]:
@@ -1212,7 +1297,9 @@ def all_package_names(self, include_virtuals: bool = False) -> List[str]:
 
     def package_path(self, name: str) -> str:
         """Get path to package.py file for this repo."""
-        return os.path.join(self.packages_path, name, package_file_name)
+        return os.path.join(
+            self.packages_path, nm.pkg_name_to_pkg_dir(name, self.package_api), package_file_name
+        )
 
     def all_package_paths(self) -> Generator[str, None, None]:
         for name in self.all_package_names():
@@ -1270,15 +1357,19 @@ def get_pkg_class(self, pkg_name: str) -> Type["spack.package_base.PackageBase"]
         package. Then extracts the package class from the module
         according to Spack's naming convention.
         """
-        namespace, pkg_name = self.partition_package_name(pkg_name)
-        class_name = nm.mod_to_class(pkg_name)
-        fullname = f"{self.full_namespace}.{pkg_name}"
+        _, pkg_name = self.partition_package_name(pkg_name)
+        fullname = f"{self.full_namespace}.{nm.pkg_name_to_pkg_dir(pkg_name, self.package_api)}"
+        if self.package_api >= (2, 0):
+            fullname += ".package"
 
+        class_name = nm.pkg_name_to_class_name(pkg_name)
+        if self.python_path and self.python_path not in sys.path:
+            sys.path.insert(0, self.python_path)
         try:
             with REPOS_FINDER.switch_repo(self._finder or self):
                 module = importlib.import_module(fullname)
-        except ImportError:
-            raise UnknownPackageError(fullname)
+        except ImportError as e:
+            raise UnknownPackageError(fullname) from e
         except Exception as e:
             msg = f"cannot load package '{pkg_name}' from the '{self.namespace}' repository: {e}"
             raise RepoError(msg) from e
@@ -1369,46 +1460,71 @@ def partition_package_name(pkg_name: str) -> Tuple[str, str]:
     return namespace, pkg_name
 
 
-def create_repo(root, namespace=None, subdir=packages_dir_name):
+def get_repo_yaml_dir(
+    root: str, namespace: Optional[str], package_api: Tuple[int, int]
+) -> Tuple[str, str]:
+    """Returns the directory where repo.yaml is located and the effective namespace."""
+    if package_api < (2, 0):
+        namespace = namespace or os.path.basename(root)
+        # This ad-hoc regex is left for historical reasons, and should not have a breaking change.
+        if not re.match(r"\w[\.\w-]*", namespace):
+            raise InvalidNamespaceError(f"'{namespace}' is not a valid namespace.")
+        return root, namespace
+
+    # Package API v2 has <root>/spack_repo/<namespace>/<subdir> structure and requires a namespace
+    if namespace is None:
+        raise InvalidNamespaceError("Namespace must be provided.")
+
+    # if namespace has dots those translate to subdirs of further namespace packages.
+    namespace_components = namespace.split(".")
+
+    if not all(nm.valid_module_name(n, package_api=package_api) for n in namespace_components):
+        raise InvalidNamespaceError(f"'{namespace}' is not a valid namespace." % namespace)
+
+    return os.path.join(root, "spack_repo", *namespace_components), namespace
+
+
+def create_repo(
+    root,
+    namespace: Optional[str] = None,
+    subdir: str = packages_dir_name,
+    package_api: Tuple[int, int] = spack.package_api_version,
+) -> Tuple[str, str]:
     """Create a new repository in root with the specified namespace.
 
     If the namespace is not provided, use basename of root.
     Return the canonicalized path and namespace of the created repository.
     """
     root = spack.util.path.canonicalize_path(root)
-    if not namespace:
-        namespace = os.path.basename(root)
+    repo_yaml_dir, namespace = get_repo_yaml_dir(os.path.abspath(root), namespace, package_api)
 
-    if not re.match(r"\w[\.\w-]*", namespace):
-        raise InvalidNamespaceError("'%s' is not a valid namespace." % namespace)
+    existed = True
+    try:
+        dir_entry = next(os.scandir(repo_yaml_dir), None)
+    except OSError as e:
+        if e.errno == errno.ENOENT:
+            existed = False
+            dir_entry = None
+        else:
+            raise BadRepoError(f"Cannot create new repo in {root}: {e}")
 
-    existed = False
-    if os.path.exists(root):
-        if os.path.isfile(root):
-            raise BadRepoError("File %s already exists and is not a directory" % root)
-        elif os.path.isdir(root):
-            if not os.access(root, os.R_OK | os.W_OK):
-                raise BadRepoError("Cannot create new repo in %s: cannot access directory." % root)
-            if os.listdir(root):
-                raise BadRepoError("Cannot create new repo in %s: directory is not empty." % root)
-        existed = True
+    if dir_entry is not None:
+        raise BadRepoError(f"Cannot create new repo in {root}: directory is not empty.")
 
-    full_path = os.path.realpath(root)
-    parent = os.path.dirname(full_path)
-    if not os.access(parent, os.R_OK | os.W_OK):
-        raise BadRepoError("Cannot create repository in %s: can't access parent!" % root)
+    config_path = os.path.join(repo_yaml_dir, repo_config_name)
+
+    subdir = _validate_and_normalize_subdir(subdir, root, package_api)
+
+    packages_path = os.path.join(repo_yaml_dir, subdir)
 
     try:
-        config_path = os.path.join(root, repo_config_name)
-        packages_path = os.path.join(root, subdir)
-
         fs.mkdirp(packages_path)
         with open(config_path, "w", encoding="utf-8") as config:
             config.write("repo:\n")
             config.write(f"  namespace: '{namespace}'\n")
             if subdir != packages_dir_name:
                 config.write(f"  subdirectory: '{subdir}'\n")
-            x, y = spack.package_api_version
+            x, y = package_api
             config.write(f"  api: v{x}.{y}\n")
 
     except OSError as e:
@@ -1421,22 +1537,27 @@ def create_repo(root, namespace=None, subdir=packages_dir_name):
 
         raise BadRepoError(
             "Failed to create new repository in %s." % root, "Caused by %s: %s" % (type(e), e)
-        )
+        ) from e
 
-    return full_path, namespace
+    return repo_yaml_dir, namespace
 
 
-def from_path(path: str) -> "Repo":
+def from_path(path: str) -> Repo:
     """Returns a repository from the path passed as input. Injects the global misc cache."""
     return Repo(path, cache=spack.caches.MISC_CACHE)
 
 
-def create_or_construct(path, namespace=None):
+def create_or_construct(
+    root: str,
+    namespace: Optional[str] = None,
+    package_api: Tuple[int, int] = spack.package_api_version,
+) -> Repo:
     """Create a repository, or just return a Repo if it already exists."""
-    if not os.path.exists(path):
-        fs.mkdirp(path)
-        create_repo(path, namespace)
-    return from_path(path)
+    repo_yaml_dir, _ = get_repo_yaml_dir(root, namespace, package_api)
+    if not os.path.exists(repo_yaml_dir):
+        fs.mkdirp(root)
+        create_repo(root, namespace=namespace, package_api=package_api)
+    return from_path(repo_yaml_dir)
 
 
 def _path(configuration=None):
@@ -1514,8 +1635,10 @@ class MockRepositoryBuilder:
     """Build a mock repository in a directory"""
 
     def __init__(self, root_directory, namespace=None):
-        namespace = namespace or "".join(random.choice(string.ascii_uppercase) for _ in range(10))
-        self.root, self.namespace = create_repo(str(root_directory), namespace)
+        namespace = namespace or "".join(random.choice(string.ascii_lowercase) for _ in range(10))
+        repo_root = os.path.join(root_directory, namespace)
+        os.mkdir(repo_root)
+        self.root, self.namespace = create_repo(repo_root, namespace)
 
     def add_package(self, name, dependencies=None):
         """Create a mock package in the repository, using a Jinja2 template.
@@ -1527,7 +1650,7 @@ def add_package(self, name, dependencies=None):
                 ``spack.dependency.default_deptype`` and ``spack.spec.Spec()`` are used.
         """
         dependencies = dependencies or []
-        context = {"cls_name": nm.mod_to_class(name), "dependencies": dependencies}
+        context = {"cls_name": nm.pkg_name_to_class_name(name), "dependencies": dependencies}
         template = spack.tengine.make_environment().get_template("mock-repository/package.pyt")
         text = template.render(context)
         package_py = self.recipe_filename(name)
@@ -1539,8 +1662,10 @@ def remove(self, name):
         package_py = self.recipe_filename(name)
         shutil.rmtree(os.path.dirname(package_py))
 
-    def recipe_filename(self, name):
-        return os.path.join(self.root, "packages", name, "package.py")
+    def recipe_filename(self, name: str):
+        return os.path.join(
+            self.root, "packages", nm.pkg_name_to_pkg_dir(name, package_api=(2, 0)), "package.py"
+        )
 
 
 class RepoError(spack.error.SpackError):
@@ -1590,7 +1715,10 @@ def __init__(self, name, repo=None):
 
                 # We need to compare the base package name
                 pkg_name = name.rsplit(".", 1)[-1]
-                similar = difflib.get_close_matches(pkg_name, repo.all_package_names())
+                try:
+                    similar = difflib.get_close_matches(pkg_name, repo.all_package_names())
+                except Exception:
+                    similar = []
 
                 if 1 <= len(similar) <= 5:
                     long_msg += "\n\nDid you mean one of the following packages?\n  "

lib/spack/spack/schema/config.py

@@ -100,7 +100,7 @@
             "allow_sgid": {"type": "boolean"},
             "install_status": {"type": "boolean"},
             "binary_index_root": {"type": "string"},
-            "url_fetch_method": {"type": "string", "enum": ["urllib", "curl"]},
+            "url_fetch_method": {"type": "string", "pattern": r"^urllib$|^curl( .*)*"},
             "additional_external_search_paths": {"type": "array", "items": {"type": "string"}},
             "binary_index_ttl": {"type": "integer", "minimum": 0},
             "aliases": {"type": "object", "patternProperties": {r"\w[\w-]*": {"type": "string"}}},

lib/spack/spack/solver/asp.py

@@ -287,9 +287,33 @@ def specify(spec):
     return spack.spec.Spec(spec)
 
 
-def remove_node(spec: spack.spec.Spec, facts: List[AspFunction]) -> List[AspFunction]:
-    """Transformation that removes all "node" and "virtual_node" from the input list of facts."""
-    return list(filter(lambda x: x.args[0] not in ("node", "virtual_node"), facts))
+def remove_facts(
+    *to_be_removed: str,
+) -> Callable[[spack.spec.Spec, List[AspFunction]], List[AspFunction]]:
+    """Returns a transformation function that removes facts from the input list of facts."""
+
+    def _remove(spec: spack.spec.Spec, facts: List[AspFunction]) -> List[AspFunction]:
+        return list(filter(lambda x: x.args[0] not in to_be_removed, facts))
+
+    return _remove
+
+
+def remove_build_deps(spec: spack.spec.Spec, facts: List[AspFunction]) -> List[AspFunction]:
+    build_deps = {x.args[2]: x.args[1] for x in facts if x.args[0] == "depends_on"}
+    result = []
+    for x in facts:
+        current_name = x.args[1]
+        if current_name in build_deps:
+            x.name = "build_requirement"
+            result.append(fn.attr("build_requirement", build_deps[current_name], x))
+            continue
+
+        if x.args[0] == "depends_on":
+            continue
+
+        result.append(x)
+
+    return result
 
 
 def all_libcs() -> Set[spack.spec.Spec]:
@@ -1190,7 +1214,7 @@ def solve(self, setup, specs, reuse=None, output=None, control=None, allow_depre
                 problem_repr += "\n" + f.read()
 
         result = None
-        conc_cache_enabled = spack.config.get("config:concretization_cache:enable", True)
+        conc_cache_enabled = spack.config.get("config:concretization_cache:enable", False)
         if conc_cache_enabled:
             result, concretization_stats = CONC_CACHE.fetch(problem_repr)
 
@@ -1287,12 +1311,8 @@ def on_model(model):
             result.raise_if_unsat()
 
             if result.satisfiable and result.unsolved_specs and setup.concretize_everything:
-                unsolved_str = Result.format_unsolved(result.unsolved_specs)
-                raise InternalConcretizerError(
-                    "Internal Spack error: the solver completed but produced specs"
-                    " that do not satisfy the request. Please report a bug at "
-                    f"https://github.com/spack/spack/issues\n\t{unsolved_str}"
-                )
+                raise OutputDoesNotSatisfyInputError(result.unsolved_specs)
+
             if conc_cache_enabled:
                 CONC_CACHE.store(problem_repr, result, self.control.statistics, test=setup.tests)
             concretization_stats = self.control.statistics
@@ -1735,15 +1755,17 @@ def define_variant(
             pkg_fact(fn.variant_condition(name, vid, cond_id))
 
         # record type so we can construct the variant when we read it back in
-        self.gen.fact(fn.variant_type(vid, variant_def.variant_type.value))
+        self.gen.fact(fn.variant_type(vid, variant_def.variant_type.string))
 
         if variant_def.sticky:
             pkg_fact(fn.variant_sticky(vid))
 
         # define defaults for this variant definition
-        defaults = variant_def.make_default().value if variant_def.multi else [variant_def.default]
-        for val in sorted(defaults):
-            pkg_fact(fn.variant_default_value_from_package_py(vid, val))
+        if variant_def.multi:
+            for val in sorted(variant_def.make_default().values):
+                pkg_fact(fn.variant_default_value_from_package_py(vid, val))
+        else:
+            pkg_fact(fn.variant_default_value_from_package_py(vid, variant_def.default))
 
         # define possible values for this variant definition
         values = variant_def.values
@@ -1771,7 +1793,9 @@ def define_variant(
 
             # make a spec indicating whether the variant has this conditional value
             variant_has_value = spack.spec.Spec()
-            variant_has_value.variants[name] = spack.variant.AbstractVariant(name, value.value)
+            variant_has_value.variants[name] = vt.VariantValue(
+                vt.VariantType.MULTI, name, (value.value,)
+            )
 
             if value.when:
                 # the conditional value is always "possible", but it imposes its when condition as
@@ -1884,7 +1908,7 @@ def condition(
 
         if not context:
             context = ConditionContext()
-            context.transform_imposed = remove_node
+            context.transform_imposed = remove_facts("node", "virtual_node")
 
         if imposed_spec:
             imposed_name = imposed_spec.name or imposed_name
@@ -1984,7 +2008,7 @@ def track_dependencies(input_spec, requirements):
                     return requirements + [fn.attr("track_dependencies", input_spec.name)]
 
                 def dependency_holds(input_spec, requirements):
-                    result = remove_node(input_spec, requirements) + [
+                    result = remove_facts("node", "virtual_node")(input_spec, requirements) + [
                         fn.attr(
                             "dependency_holds", pkg.name, input_spec.name, dt.flag_to_string(t)
                         )
@@ -2174,7 +2198,10 @@ def emit_facts_from_requirement_rules(self, rules: List[RequirementRule]):
                         pkg_name, ConstraintOrigin.REQUIRE
                     )
                     if not virtual:
-                        context.transform_imposed = remove_node
+                        context.transform_required = remove_build_deps
+                        context.transform_imposed = remove_facts(
+                            "node", "virtual_node", "depends_on"
+                        )
                     # else: for virtuals we want to emit "node" and
                     # "virtual_node" in imposed specs
 
@@ -2236,16 +2263,18 @@ def external_packages(self):
             if pkg_name not in self.pkgs:
                 continue
 
-            self.gen.h2(f"External package: {pkg_name}")
             # Check if the external package is buildable. If it is
             # not then "external(<pkg>)" is a fact, unless we can
             # reuse an already installed spec.
             external_buildable = data.get("buildable", True)
+            externals = data.get("externals", [])
+            if not external_buildable or externals:
+                self.gen.h2(f"External package: {pkg_name}")
+
             if not external_buildable:
                 self.gen.fact(fn.buildable_false(pkg_name))
 
             # Read a list of all the specs for this package
-            externals = data.get("externals", [])
             candidate_specs = [
                 spack.spec.parse_with_version_concrete(x["spec"]) for x in externals
             ]
@@ -2334,6 +2363,8 @@ def preferred_variants(self, pkg_name):
         if not preferred_variants:
             return
 
+        self.gen.h2(f"Package preferences: {pkg_name}")
+
         for variant_name in sorted(preferred_variants):
             variant = preferred_variants[variant_name]
 
@@ -2346,7 +2377,7 @@ def preferred_variants(self, pkg_name):
                 )
                 continue
 
-            for value in variant.value_as_tuple:
+            for value in variant.values:
                 for variant_def in variant_defs:
                     self.variant_values_from_specs.add((pkg_name, id(variant_def), value))
                 self.gen.fact(
@@ -2461,10 +2492,10 @@ def _spec_clauses(
             # TODO: variant="*" means 'variant is defined to something', which used to
             # be meaningless in concretization, as all variants had to be defined. But
             # now that variants can be conditional, it should force a variant to exist.
-            if variant.value == ("*",):
+            if not variant.values:
                 continue
 
-            for value in variant.value_as_tuple:
+            for value in variant.values:
                 # ensure that the value *can* be valid for the spec
                 if spec.name and not spec.concrete and not spack.repo.PATH.is_virtual(spec.name):
                     variant_defs = vt.prevalidate_variant_value(
@@ -2574,6 +2605,16 @@ def _spec_clauses(
                     # already-installed concrete specs.
                     if concrete_build_deps or dspec.depflag != dt.BUILD:
                         clauses.append(fn.attr("hash", dep.name, dep.dag_hash()))
+                    elif not concrete_build_deps and dspec.depflag:
+                        clauses.append(
+                            fn.attr(
+                                "concrete_build_dependency", spec.name, dep.name, dep.dag_hash()
+                            )
+                        )
+                        for virtual_name in dspec.virtuals:
+                            clauses.append(
+                                fn.attr("virtual_on_build_edge", spec.name, dep.name, virtual_name)
+                            )
 
                 # if the spec is abstract, descend into dependencies.
                 # if it's concrete, then the hashes above take care of dependency
@@ -2997,14 +3038,46 @@ def setup(
         """
         reuse = reuse or []
         check_packages_exist(specs)
+        self.gen = ProblemInstanceBuilder()
 
-        node_counter = create_counter(specs, tests=self.tests, possible_graph=self.possible_graph)
+        # Compute possible compilers first, so we can record which dependencies they might inject
+        _ = spack.compilers.config.all_compilers(init_config=True)
+
+        # Get compilers from buildcache only if injected through "reuse" specs
+        supported_compilers = spack.compilers.config.supported_compilers()
+        compilers_from_reuse = {
+            x for x in reuse if x.name in supported_compilers and not x.external
+        }
+        candidate_compilers, self.rejected_compilers = possible_compilers(
+            configuration=spack.config.CONFIG
+        )
+        for x in candidate_compilers:
+            if x.external or x in reuse:
+                continue
+            reuse.append(x)
+            for dep in x.traverse(root=False, deptype="run"):
+                reuse.extend(dep.traverse(deptype=("link", "run")))
+
+        candidate_compilers.update(compilers_from_reuse)
+        self.possible_compilers = list(candidate_compilers)
+        self.possible_compilers.sort()  # type: ignore[call-overload]
+
+        self.gen.h1("Runtimes")
+        injected_dependencies = self.define_runtime_constraints()
+
+        node_counter = create_counter(
+            specs + injected_dependencies, tests=self.tests, possible_graph=self.possible_graph
+        )
         self.possible_virtuals = node_counter.possible_virtuals()
         self.pkgs = node_counter.possible_dependencies()
         self.libcs = sorted(all_libcs())  # type: ignore[type-var]
 
         # Fail if we already know an unreachable node is requested
         for spec in specs:
+            # concrete roots don't need their dependencies verified
+            if spec.concrete:
+                continue
+
             missing_deps = [
                 str(d)
                 for d in spec.traverse()
@@ -3017,7 +3090,6 @@ def setup(
             if node.namespace is not None:
                 self.explicitly_required_namespaces[node.name] = node.namespace
 
-        self.gen = ProblemInstanceBuilder()
         self.gen.h1("Generic information")
         if using_libc_compatibility():
             for libc in self.libcs:
@@ -3046,27 +3118,6 @@ def setup(
 
         specs = tuple(specs)  # ensure compatible types to add
 
-        _ = spack.compilers.config.all_compilers(init_config=True)
-
-        # Get compilers from buildcache only if injected through "reuse" specs
-        supported_compilers = spack.compilers.config.supported_compilers()
-        compilers_from_reuse = {
-            x for x in reuse if x.name in supported_compilers and not x.external
-        }
-        candidate_compilers, self.rejected_compilers = possible_compilers(
-            configuration=spack.config.CONFIG
-        )
-        for x in candidate_compilers:
-            if x.external or x in reuse:
-                continue
-            reuse.append(x)
-            for dep in x.traverse(root=False, deptype="run"):
-                reuse.extend(dep.traverse(deptype=("link", "run")))
-
-        candidate_compilers.update(compilers_from_reuse)
-        self.possible_compilers = list(candidate_compilers)
-        self.possible_compilers.sort()  # type: ignore[call-overload]
-
         self.gen.h1("Reusable concrete specs")
         self.define_concrete_input_specs(specs, self.pkgs)
         if reuse:
@@ -3118,7 +3169,6 @@ def setup(
         for pkg in sorted(self.pkgs):
             self.gen.h2("Package rules: %s" % pkg)
             self.pkg_rules(pkg, tests=self.tests)
-            self.gen.h2("Package preferences: %s" % pkg)
             self.preferred_variants(pkg)
 
         self.gen.h1("Special variants")
@@ -3138,9 +3188,6 @@ def setup(
         self.gen.h1("Variant Values defined in specs")
         self.define_variant_values()
 
-        self.gen.h1("Runtimes")
-        self.define_runtime_constraints()
-
         self.gen.h1("Version Constraints")
         self.collect_virtual_constraints()
         self.define_version_constraints()
@@ -3174,8 +3221,10 @@ def visit(node):
         path = os.path.join(parent_dir, "concretize.lp")
         parse_files([path], visit)
 
-    def define_runtime_constraints(self):
-        """Define the constraints to be imposed on the runtimes"""
+    def define_runtime_constraints(self) -> List[spack.spec.Spec]:
+        """Define the constraints to be imposed on the runtimes, and returns a list of
+        injected packages.
+        """
         recorder = RuntimePropertyRecorder(self)
 
         for compiler in self.possible_compilers:
@@ -3191,12 +3240,13 @@ def define_runtime_constraints(self):
 
             # FIXME (compiler as nodes): think of using isinstance(compiler_cls, WrappedCompiler)
             # Add a dependency on the compiler wrapper
-            recorder("*").depends_on(
-                "compiler-wrapper",
-                when=f"%{compiler.name}@{compiler.versions}",
-                type="build",
-                description=f"Add the compiler wrapper when using {compiler}",
-            )
+            for language in ("c", "cxx", "fortran"):
+                recorder("*").depends_on(
+                    "compiler-wrapper",
+                    when=f"%[virtuals={language}] {compiler.name}@{compiler.versions}",
+                    type="build",
+                    description=f"Add the compiler wrapper when using {compiler} for {language}",
+                )
 
             if not using_libc_compatibility():
                 continue
@@ -3225,6 +3275,7 @@ def define_runtime_constraints(self):
                 )
 
         recorder.consume_facts()
+        return sorted(recorder.injected_dependencies)
 
     def literal_specs(self, specs):
         for spec in sorted(specs):
@@ -3257,15 +3308,13 @@ def literal_specs(self, specs):
                     # These facts are needed to compute the "condition_set" of the root
                     pkg_name = clause.args[1]
                     self.gen.fact(fn.mentioned_in_literal(trigger_id, root_name, pkg_name))
-                elif clause_name == "depends_on":
-                    pkg_name = clause.args[2]
-                    self.gen.fact(fn.mentioned_in_literal(trigger_id, root_name, pkg_name))
 
             requirements.append(
                 fn.attr(
                     "virtual_root" if spack.repo.PATH.is_virtual(spec.name) else "root", spec.name
                 )
             )
+            requirements = [x for x in requirements if x.args[0] != "depends_on"]
             cache[imposed_spec_key] = (effect_id, requirements)
             self.gen.fact(fn.pkg_fact(spec.name, fn.condition_effect(condition_id, effect_id)))
 
@@ -3489,6 +3538,7 @@ def __init__(self, setup):
         self._setup = setup
         self.rules = []
         self.runtime_conditions = set()
+        self.injected_dependencies = set()
         # State of this object set in the __call__ method, and reset after
         # each directive-like method
         self.current_package = None
@@ -3527,6 +3577,7 @@ def depends_on(self, dependency_str: str, *, when: str, type: str, description:
         if dependency_spec.versions != vn.any_version:
             self._setup.version_constraints.add((dependency_spec.name, dependency_spec.versions))
 
+        self.injected_dependencies.add(dependency_spec)
         body_str, node_variable = self.rule_body_from(when_spec)
 
         head_clauses = self._setup.spec_clauses(dependency_spec, body=False)
@@ -3588,11 +3639,9 @@ def rule_body_from(self, when_spec: "spack.spec.Spec") -> Tuple[str, str]:
                 # (avoid adding virtuals everywhere, if a single edge needs it)
                 _, provider, virtual = clause.args
                 clause.args = "virtual_on_edge", node_placeholder, provider, virtual
-        body_str = (
-            f"  {f',{os.linesep}  '.join(str(x) for x in body_clauses)},\n"
-            f"  not external({node_variable}),\n"
-            f"  not runtime(Package)"
-        ).replace(f'"{node_placeholder}"', f"{node_variable}")
+        body_str = ",\n".join(f"  {x}" for x in body_clauses)
+        body_str += f",\n  not external({node_variable})"
+        body_str = body_str.replace(f'"{node_placeholder}"', f"{node_variable}")
         for old, replacement in when_substitutions.items():
             body_str = body_str.replace(old, replacement)
         return body_str, node_variable
@@ -3682,20 +3731,21 @@ def consume_facts(self):
         """Consume the facts collected by this object, and emits rules and
         facts for the runtimes.
         """
+        self._setup.gen.h2("Runtimes: declarations")
+        runtime_pkgs = sorted(
+            {x.name for x in self.injected_dependencies if not spack.repo.PATH.is_virtual(x.name)}
+        )
+        for runtime_pkg in runtime_pkgs:
+            self._setup.gen.fact(fn.runtime(runtime_pkg))
+        self._setup.gen.newline()
+
         self._setup.gen.h2("Runtimes: rules")
         self._setup.gen.newline()
         for rule in self.rules:
             self._setup.gen.append(rule)
+        self._setup.gen.newline()
 
-        self._setup.gen.h2("Runtimes: conditions")
-        for runtime_pkg in spack.repo.PATH.packages_with_tags("runtime"):
-            self._setup.gen.fact(fn.runtime(runtime_pkg))
-            self._setup.gen.fact(fn.possible_in_link_run(runtime_pkg))
-            self._setup.gen.newline()
-            # Inject version rules for runtimes (versions are declared based
-            # on the available compilers)
-            self._setup.pkg_version_rules(runtime_pkg)
-
+        self._setup.gen.h2("Runtimes: requirements")
         for imposed_spec, when_spec in sorted(self.runtime_conditions):
             msg = f"{when_spec} requires {imposed_spec} at runtime"
             _ = self._setup.condition(when_spec, imposed_spec=imposed_spec, msg=msg)
@@ -3782,13 +3832,13 @@ def node_os(self, node, os):
     def node_target(self, node, target):
         self._arch(node).target = target
 
-    def variant_selected(self, node, name, value, variant_type, variant_id):
+    def variant_selected(self, node, name: str, value: str, variant_type: str, variant_id):
         spec = self._specs[node]
         variant = spec.variants.get(name)
         if not variant:
-            spec.variants[name] = vt.VariantType(variant_type).variant_class(name, value)
+            spec.variants[name] = vt.VariantValue.from_concretizer(name, value, variant_type)
         else:
-            assert variant_type == vt.VariantType.MULTI.value, (
+            assert variant_type == "multi", (
                 f"Can't have multiple values for single-valued variant: "
                 f"{node}, {name}, {value}, {variant_type}, {variant_id}"
             )
@@ -3812,6 +3862,17 @@ def external_spec_selected(self, node, idx):
         )
         self._specs[node].extra_attributes = spec_info.get("extra_attributes", {})
 
+        # Annotate compiler specs from externals
+        external_spec = spack.spec.Spec(spec_info["spec"])
+        external_spec_deps = external_spec.dependencies()
+        if len(external_spec_deps) > 1:
+            raise InvalidExternalError(
+                f"external spec {spec_info['spec']} cannot have more than one dependency"
+            )
+        elif len(external_spec_deps) == 1:
+            compiler_str = external_spec_deps[0]
+            self._specs[node].annotations.with_compiler(spack.spec.Spec(compiler_str))
+
         # If this is an extension, update the dependencies to include the extendee
         package = spack.repo.PATH.get_pkg_class(self._specs[node].fullname)(self._specs[node])
         extendee_spec = package.extendee_spec
@@ -3830,7 +3891,7 @@ def virtual_on_edge(self, parent_node, provider_node, virtual):
         provider_spec = self._specs[provider_node]
         dependencies = [x for x in dependencies if id(x.spec) == id(provider_spec)]
         assert len(dependencies) == 1, f"{virtual}: {provider_node.pkg}"
-        dependencies[0].update_virtuals((virtual,))
+        dependencies[0].update_virtuals(virtual)
 
     def reorder_flags(self):
         """For each spec, determine the order of compiler flags applied to it.
@@ -4167,10 +4228,10 @@ def _inject_patches_variant(root: spack.spec.Spec) -> None:
             continue
 
         patches = list(spec_to_patches[id(spec)])
-        variant: vt.MultiValuedVariant = spec.variants.setdefault(
+        variant: vt.VariantValue = spec.variants.setdefault(
             "patches", vt.MultiValuedVariant("patches", ())
         )
-        variant.value = tuple(p.sha256 for p in patches)
+        variant.set(*(p.sha256 for p in patches))
         # FIXME: Monkey patches variant to store patches order
         ordered_hashes = [(*p.ordering_key, p.sha256) for p in patches if p.ordering_key]
         ordered_hashes.sort()
@@ -4638,13 +4699,9 @@ def solve_in_rounds(
                 break
 
             if not result.specs:
-                # This is also a problem: no specs were solved for, which
-                # means we would be in a loop if we tried again
-                unsolved_str = Result.format_unsolved(result.unsolved_specs)
-                raise InternalConcretizerError(
-                    "Internal Spack error: a subset of input specs could not"
-                    f" be solved for.\n\t{unsolved_str}"
-                )
+                # This is also a problem: no specs were solved for, which means we would be in a
+                # loop if we tried again
+                raise OutputDoesNotSatisfyInputError(result.unsolved_specs)
 
             input_specs = list(x for (x, y) in result.unsolved_specs)
             for spec in result.specs:
@@ -4674,6 +4731,19 @@ def __init__(self, msg):
         self.constraint_type = None
 
 
+class OutputDoesNotSatisfyInputError(InternalConcretizerError):
+
+    def __init__(
+        self, input_to_output: List[Tuple[spack.spec.Spec, Optional[spack.spec.Spec]]]
+    ) -> None:
+        self.input_to_output = input_to_output
+        super().__init__(
+            "internal solver error: the solver completed but produced specs"
+            " that do not satisfy the request. Please report a bug at "
+            f"https://github.com/spack/spack/issues\n\t{Result.format_unsolved(input_to_output)}"
+        )
+
+
 class SolverError(InternalConcretizerError):
     """For cases where the solver is unable to produce a solution.
 
@@ -4706,3 +4776,7 @@ class InvalidSpliceError(spack.error.SpackError):
 
 class NoCompilerFoundError(spack.error.SpackError):
     """Raised when there is no possible compiler"""
+
+
+class InvalidExternalError(spack.error.SpackError):
+    """Raised when there is no possible compiler"""

lib/spack/spack/solver/concretize.lp

@@ -175,12 +175,24 @@ trigger_node(TriggerID, Node, Node) :-
 
 % Since we trigger the existence of literal nodes from a condition, we need to construct the condition_set/2
 mentioned_in_literal(Root, Mentioned) :- mentioned_in_literal(TriggerID, Root, Mentioned), solve_literal(TriggerID).
-condition_set(node(min_dupe_id, Root), node(min_dupe_id, Root)) :-  mentioned_in_literal(Root, Root).
+literal_node(Root, node(min_dupe_id, Root)) :-  mentioned_in_literal(Root, Root).
 
-1 { condition_set(node(min_dupe_id, Root), node(0..Y-1, Mentioned)) : max_dupes(Mentioned, Y) } 1 :-
+1 { literal_node(Root, node(0..Y-1, Mentioned)) : max_dupes(Mentioned, Y) } 1 :-
   mentioned_in_literal(Root, Mentioned), Mentioned != Root,
   internal_error("must have exactly one condition_set for literals").
 
+1 { build_dependency_of_literal_node(LiteralNode, node(0..Y-1, BuildDependency)) : max_dupes(BuildDependency, Y) } 1 :-
+  literal_node(Root, LiteralNode),
+  build(LiteralNode),
+  not external(LiteralNode),
+  attr("build_requirement", LiteralNode, build_requirement("node", BuildDependency)).
+
+condition_set(node(min_dupe_id, Root), LiteralNode) :- literal_node(Root, LiteralNode).
+condition_set(LiteralNode, BuildNode) :- build_dependency_of_literal_node(LiteralNode, BuildNode).
+
+:- build_dependency_of_literal_node(LiteralNode, BuildNode),
+   not attr("depends_on", LiteralNode, BuildNode, "build").
+
 % Discriminate between "roots" that have been explicitly requested, and roots that are deduced from "virtual roots"
 explicitly_requested_root(node(min_dupe_id, Package)) :-
   solve_literal(TriggerID),
@@ -472,10 +484,53 @@ provider(ProviderNode, VirtualNode) :- attr("provider_set", ProviderNode, Virtua
      imposed_constraint(ID, "depends_on", A1, A2, A3),
      internal_error("Build deps must land in exactly one duplicate").
 
-1 { build_requirement(node(X, Parent), node(0..Y-1, BuildDependency)) : max_dupes(BuildDependency, Y) } 1
+% If the parent is built, then we have a build_requirement on another node. For concrete nodes,
+% or external nodes, we don't since we are trimming their build dependencies.
+1 { attr("depends_on",  node(X, Parent), node(0..Y-1, BuildDependency), "build") : max_dupes(BuildDependency, Y) } 1
   :- attr("build_requirement", node(X, Parent), build_requirement("node", BuildDependency)),
-     impose(ID, node(X, Parent)),
-     imposed_constraint(ID,"build_requirement",Parent,_).
+     build(node(X, Parent)),
+     not external(node(X, Parent)).
+
+% Concrete nodes
+:- attr("build_requirement", ParentNode, build_requirement("node", BuildDependency)),
+   concrete(ParentNode),
+   not attr("concrete_build_dependency", ParentNode, BuildDependency, _).
+
+:- attr("build_requirement", ParentNode, build_requirement("node_version_satisfies", BuildDependency, Constraint)),
+   attr("concrete_build_dependency", ParentNode, BuildDependency, BuildDependencyHash),
+   not 1 { pkg_fact(BuildDependency, version_satisfies(Constraint, Version)) : hash_attr(BuildDependencyHash, "version", BuildDependency, Version) } 1.
+
+:- attr("build_requirement", ParentNode, build_requirement("provider_set", BuildDependency, Virtual)),
+   attr("concrete_build_dependency", ParentNode, BuildDependency, BuildDependencyHash),
+   attr("virtual_on_build_edge", ParentNode, BuildDependency, Virtual),
+   not 1 { pkg_fact(BuildDependency, version_satisfies(Constraint, Version)) : hash_attr(BuildDependencyHash, "version", BuildDependency, Version) } 1.
+
+% External nodes
+:- attr("build_requirement", ParentNode, build_requirement("node", BuildDependency)),
+   external(ParentNode),
+   not attr("external_build_requirement", ParentNode, build_requirement("node", BuildDependency)).
+
+candidate_external_version(Constraint, BuildDependency, Version)
+  :- attr("build_requirement", ParentNode, build_requirement("node_version_satisfies", BuildDependency, Constraint)),
+     external(ParentNode),
+     pkg_fact(BuildDependency, version_satisfies(Constraint, Version)).
+
+error(100, "External {0} cannot satisfy both {1} and {2}", BuildDependency, LiteralConstraint, ExternalConstraint)
+  :- attr("build_requirement", ParentNode, build_requirement("node_version_satisfies", BuildDependency, LiteralConstraint)),
+     external(ParentNode),
+     attr("external_build_requirement", ParentNode, build_requirement("node_version_satisfies", BuildDependency, ExternalConstraint)),
+     not 1 { pkg_fact(BuildDependency, version_satisfies(ExternalConstraint, Version)) : candidate_external_version(LiteralConstraint, BuildDependency, Version) }.
+
+
+% Asking for gcc@10 %gcc@9 shouldn't give us back an external gcc@10, just because of the hack
+% we have on externals
+:- attr("build_requirement", node(X, Parent), build_requirement("node", BuildDependency)),
+   Parent == BuildDependency,
+   external(node(X, Parent)).
+
+build_requirement(node(X, Parent), node(Y, BuildDependency)) :-
+  attr("depends_on", node(X, Parent), node(Y, BuildDependency), "build"),
+  attr("build_requirement", node(X, Parent), build_requirement("node", BuildDependency)).
 
 1 { virtual_build_requirement(ParentNode, node(0..Y-1, Virtual)) : max_dupes(Virtual, Y) } 1
   :- attr("dependency_holds", ParentNode, Virtual, "build"),
@@ -496,7 +551,6 @@ attr("node_version_satisfies", node(X, BuildDependency), Constraint) :-
   attr("build_requirement", ParentNode, build_requirement("node_version_satisfies", BuildDependency, Constraint)),
   build_requirement(ParentNode, node(X, BuildDependency)).
 
-attr("depends_on",  node(X, Parent), node(Y, BuildDependency), "build") :- build_requirement(node(X, Parent), node(Y, BuildDependency)).
 
 1 { attr("provider_set", node(X, BuildDependency), node(0..Y-1, Virtual)) : max_dupes(Virtual, Y) } 1 :-
   attr("build_requirement", ParentNode, build_requirement("provider_set", BuildDependency, Virtual)),
@@ -882,6 +936,12 @@ requirement_weight(node(ID, Package), Group, W) :-
   requirement_policy(Package, Group, "one_of"),
   requirement_group_satisfied(node(ID, Package), Group).
 
+ { attr("build_requirement", node(ID, Package), BuildRequirement) : condition_requirement(TriggerID, "build_requirement", Package, BuildRequirement) } :-
+  pkg_fact(Package, condition_trigger(ConditionID, TriggerID)),
+  requirement_group_member(ConditionID, Package, Group),
+  activate_requirement(node(ID, Package), Group),
+  requirement_group(Package, Group).
+
 requirement_group_satisfied(node(ID, Package), X) :-
   1 { condition_holds(Y, node(ID, Package)) : requirement_group_member(Y, Package, X) } ,
   requirement_policy(Package, X, "any_of"),