Add new custom markers to unit tests (#33862)

* Add "only_clingo", "only_original" and "not_on_windows" markers

* Modify tests to use the "not_on_windows" marker

* Mark tests that run only with clingo

* Mark tests that run only with the original concretizer

.github/workflows/unit_tests.yaml

@@ -165,6 +165,7 @@ jobs:
     - name: Install Python packages
       run: |
           pip install --upgrade pip setuptools pytest coverage[toml] pytest-cov clingo pytest-xdist
+          pip install --upgrade flake8 "isort>=4.3.5" "mypy>=0.900" "click" "black"
     - name: Setup git configuration
       run: |
           # Need this for the git tests to succeed.

etc/spack/defaults/concretizer.yaml

@@ -36,3 +36,9 @@ concretizer:
   # on each root spec, allowing different versions and variants of the same package in
   # an environment.
   unify: true
+  # Option to deal with possible duplicate nodes (i.e. different nodes from the same package) in the DAG.
+  duplicates:
+    # "none": allows a single node for any package in the DAG.
+    # "minimal": allows the duplication of 'build-tools' nodes only (e.g. py-setuptools, cmake etc.)
+    # "full" (experimental): allows separation of the entire build-tool stack (e.g. the entire "cmake" subDAG)
+    strategy: none

etc/spack/defaults/packages.yaml

@@ -60,6 +60,7 @@ packages:
       xxd: [xxd-standalone, vim]
       yacc: [bison, byacc]
       ziglang: [zig]
+      zlib-api: [zlib, zlib-ng+compat]
     permissions:
       read: world
       write: user

lib/spack/docs/bootstrapping.rst

@@ -32,9 +32,14 @@ can't be found. You can readily check if any prerequisite for using Spack is mis
 
    Spack will take care of bootstrapping any missing dependency marked as [B]. Dependencies marked as [-] are instead required to be found on the system.
 
+   % echo $?
+   1
+
 In the case of the output shown above Spack detected that both ``clingo`` and ``gnupg``
 are missing and it's giving detailed information on why they are needed and whether
-they can be bootstrapped. Running a command that concretize a spec, like:
+they can be bootstrapped. The return code of this command summarizes the results, if any
+dependencies are missing the return code is ``1``, otherwise ``0``. Running a command that
+concretizes a spec, like:
 
 .. code-block:: console
 
@@ -44,7 +49,7 @@ they can be bootstrapped. Running a command that concretize a spec, like:
    ==> Installing "clingo-bootstrap@spack%apple-clang@12.0.0~docs~ipo+python build_type=Release arch=darwin-catalina-x86_64" from a buildcache
    [ ... ]
 
-triggers the bootstrapping of clingo from pre-built binaries as expected.
+automatically triggers the bootstrapping of clingo from pre-built binaries as expected.
 
 Users can also bootstrap all the dependencies needed by Spack in a single command, which
 might be useful to setup containers or other similar environments:

lib/spack/docs/build_systems/inteloneapipackage.rst

@@ -104,11 +104,13 @@ Clone `spack-configs <https://github.com/spack/spack-configs>`_ repo and activat
 
 `Intel oneAPI CPU environment <https://github.com/spack/spack-configs/blob/main/INTEL/CPU/spack.yaml>`_  contains applications tested and validated by Intel, this list is constantly extended. And currently it supports:
 
+- `Devito <https://www.devitoproject.org/>`_
 - `GROMACS <https://www.gromacs.org/>`_
 - `HPCG <https://www.hpcg-benchmark.org/>`_
 - `HPL <https://netlib.org/benchmark/hpl/>`_
 - `LAMMPS <https://www.lammps.org/#gsc.tab=0>`_
 - `OpenFOAM <https://www.openfoam.com/>`_
+- `Quantum Espresso <https://www.quantum-espresso.org/>`_
 - `STREAM <https://www.cs.virginia.edu/stream/>`_
 - `WRF <https://github.com/wrf-model/WRF>`_
 

lib/spack/docs/packaging_guide.rst

@@ -2243,7 +2243,7 @@ looks like this:
        url      = "http://www.openssl.org/source/openssl-1.0.1h.tar.gz"
 
        version("1.0.1h", md5="8d6d684a9430d5cc98a62a5d8fbda8cf")
-       depends_on("zlib")
+       depends_on("zlib-api")
 
        parallel = False
 

lib/spack/docs/requirements.txt

@@ -1,13 +1,13 @@
 sphinx==6.2.1
 sphinxcontrib-programoutput==0.17
-sphinx_design==0.4.1
+sphinx_design==0.5.0
 sphinx-rtd-theme==1.2.2
 python-levenshtein==0.21.1
 docutils==0.18.1
-pygments==2.15.1
-urllib3==2.0.3
+pygments==2.16.1
+urllib3==2.0.4
 pytest==7.4.0
 isort==5.12.0
-black==23.1.0
-flake8==6.0.0
-mypy==1.4.1
+black==23.7.0
+flake8==6.1.0
+mypy==1.5.0

lib/spack/llnl/util/lock.py

@@ -143,7 +143,7 @@ def get_fh(self, path: str) -> IO:
     def release_by_stat(self, stat):
         key = (stat.st_dev, stat.st_ino, os.getpid())
         open_file = self._descriptors.get(key)
-        assert open_file, "Attempted to close non-existing inode: %s" % stat.st_inode
+        assert open_file, "Attempted to close non-existing inode: %s" % stat.st_ino
 
         open_file.refs -= 1
         if not open_file.refs:

lib/spack/llnl/util/tty/log.py

@@ -780,7 +780,7 @@ def __enter__(self):
             raise RuntimeError("file argument must be set by __init__ ")
 
         # Open both write and reading on logfile
-        if type(self.logfile) == io.StringIO:
+        if isinstance(self.logfile, io.StringIO):
             self._ioflag = True
             # cannot have two streams on tempfile, so we must make our own
             sys.stdout = self.logfile

lib/spack/spack/audit.py

@@ -286,7 +286,7 @@ def _check_build_test_callbacks(pkgs, error_cls):
     """Ensure stand-alone test method is not included in build-time callbacks"""
     errors = []
     for pkg_name in pkgs:
-        pkg_cls = spack.repo.path.get_pkg_class(pkg_name)
+        pkg_cls = spack.repo.PATH.get_pkg_class(pkg_name)
         test_callbacks = getattr(pkg_cls, "build_time_test_callbacks", None)
 
         # TODO (post-34236): "test*"->"test_*" once remove deprecated methods
@@ -312,7 +312,7 @@ def _check_patch_urls(pkgs, error_cls):
 
     errors = []
     for pkg_name in pkgs:
-        pkg_cls = spack.repo.path.get_pkg_class(pkg_name)
+        pkg_cls = spack.repo.PATH.get_pkg_class(pkg_name)
         for condition, patches in pkg_cls.patches.items():
             for patch in patches:
                 if not isinstance(patch, spack.patch.UrlPatch):
@@ -342,7 +342,7 @@ def _search_for_reserved_attributes_names_in_packages(pkgs, error_cls):
     errors = []
     for pkg_name in pkgs:
         name_definitions = collections.defaultdict(list)
-        pkg_cls = spack.repo.path.get_pkg_class(pkg_name)
+        pkg_cls = spack.repo.PATH.get_pkg_class(pkg_name)
 
         for cls_item in inspect.getmro(pkg_cls):
             for name in RESERVED_NAMES:
@@ -383,7 +383,7 @@ def _ensure_packages_are_pickeleable(pkgs, error_cls):
     """Ensure that package objects are pickleable"""
     errors = []
     for pkg_name in pkgs:
-        pkg_cls = spack.repo.path.get_pkg_class(pkg_name)
+        pkg_cls = spack.repo.PATH.get_pkg_class(pkg_name)
         pkg = pkg_cls(spack.spec.Spec(pkg_name))
         try:
             pickle.dumps(pkg)
@@ -424,7 +424,7 @@ def _ensure_all_versions_can_produce_a_fetcher(pkgs, error_cls):
     """Ensure all versions in a package can produce a fetcher"""
     errors = []
     for pkg_name in pkgs:
-        pkg_cls = spack.repo.path.get_pkg_class(pkg_name)
+        pkg_cls = spack.repo.PATH.get_pkg_class(pkg_name)
         pkg = pkg_cls(spack.spec.Spec(pkg_name))
         try:
             spack.fetch_strategy.check_pkg_attributes(pkg)
@@ -449,7 +449,7 @@ def _ensure_docstring_and_no_fixme(pkgs, error_cls):
     ]
     for pkg_name in pkgs:
         details = []
-        filename = spack.repo.path.filename_for_package_name(pkg_name)
+        filename = spack.repo.PATH.filename_for_package_name(pkg_name)
         with open(filename, "r") as package_file:
             for i, line in enumerate(package_file):
                 pattern = next((r for r in fixme_regexes if r.search(line)), None)
@@ -461,7 +461,7 @@ def _ensure_docstring_and_no_fixme(pkgs, error_cls):
             error_msg = "Package '{}' contains boilerplate that need to be removed"
             errors.append(error_cls(error_msg.format(pkg_name), details))
 
-        pkg_cls = spack.repo.path.get_pkg_class(pkg_name)
+        pkg_cls = spack.repo.PATH.get_pkg_class(pkg_name)
         if not pkg_cls.__doc__:
             error_msg = "Package '{}' miss a docstring"
             errors.append(error_cls(error_msg.format(pkg_name), []))
@@ -474,7 +474,7 @@ def _ensure_all_packages_use_sha256_checksums(pkgs, error_cls):
     """Ensure no packages use md5 checksums"""
     errors = []
     for pkg_name in pkgs:
-        pkg_cls = spack.repo.path.get_pkg_class(pkg_name)
+        pkg_cls = spack.repo.PATH.get_pkg_class(pkg_name)
         if pkg_cls.manual_download:
             continue
 
@@ -511,7 +511,7 @@ def _ensure_env_methods_are_ported_to_builders(pkgs, error_cls):
     """Ensure that methods modifying the build environment are ported to builder classes."""
     errors = []
     for pkg_name in pkgs:
-        pkg_cls = spack.repo.path.get_pkg_class(pkg_name)
+        pkg_cls = spack.repo.PATH.get_pkg_class(pkg_name)
         buildsystem_variant, _ = pkg_cls.variants["build_system"]
         buildsystem_names = [getattr(x, "value", x) for x in buildsystem_variant.values]
         builder_cls_names = [spack.builder.BUILDER_CLS[x].__name__ for x in buildsystem_names]
@@ -538,7 +538,7 @@ def _linting_package_file(pkgs, error_cls):
     """Check for correctness of links"""
     errors = []
     for pkg_name in pkgs:
-        pkg_cls = spack.repo.path.get_pkg_class(pkg_name)
+        pkg_cls = spack.repo.PATH.get_pkg_class(pkg_name)
 
         # Does the homepage have http, and if so, does https work?
         if pkg_cls.homepage.startswith("http://"):
@@ -562,7 +562,7 @@ def _unknown_variants_in_directives(pkgs, error_cls):
     """Report unknown or wrong variants in directives for this package"""
     errors = []
     for pkg_name in pkgs:
-        pkg_cls = spack.repo.path.get_pkg_class(pkg_name)
+        pkg_cls = spack.repo.PATH.get_pkg_class(pkg_name)
 
         # Check "conflicts" directive
         for conflict, triggers in pkg_cls.conflicts.items():
@@ -628,15 +628,15 @@ def _unknown_variants_in_dependencies(pkgs, error_cls):
     """Report unknown dependencies and wrong variants for dependencies"""
     errors = []
     for pkg_name in pkgs:
-        pkg_cls = spack.repo.path.get_pkg_class(pkg_name)
-        filename = spack.repo.path.filename_for_package_name(pkg_name)
+        pkg_cls = spack.repo.PATH.get_pkg_class(pkg_name)
+        filename = spack.repo.PATH.filename_for_package_name(pkg_name)
         for dependency_name, dependency_data in pkg_cls.dependencies.items():
             # No need to analyze virtual packages
-            if spack.repo.path.is_virtual(dependency_name):
+            if spack.repo.PATH.is_virtual(dependency_name):
                 continue
 
             try:
-                dependency_pkg_cls = spack.repo.path.get_pkg_class(dependency_name)
+                dependency_pkg_cls = spack.repo.PATH.get_pkg_class(dependency_name)
             except spack.repo.UnknownPackageError:
                 # This dependency is completely missing, so report
                 # and continue the analysis
@@ -675,7 +675,7 @@ def _ensure_variant_defaults_are_parsable(pkgs, error_cls):
     """Ensures that variant defaults are present and parsable from cli"""
     errors = []
     for pkg_name in pkgs:
-        pkg_cls = spack.repo.path.get_pkg_class(pkg_name)
+        pkg_cls = spack.repo.PATH.get_pkg_class(pkg_name)
         for variant_name, entry in pkg_cls.variants.items():
             variant, _ = entry
             default_is_parsable = (
@@ -709,18 +709,33 @@ def _ensure_variant_defaults_are_parsable(pkgs, error_cls):
     return errors
 
 
+@package_directives
+def _ensure_variants_have_descriptions(pkgs, error_cls):
+    """Ensures that all variants have a description."""
+    errors = []
+    for pkg_name in pkgs:
+        pkg_cls = spack.repo.PATH.get_pkg_class(pkg_name)
+        for variant_name, entry in pkg_cls.variants.items():
+            variant, _ = entry
+            if not variant.description:
+                error_msg = "Variant '{}' in package '{}' is missing a description"
+                errors.append(error_cls(error_msg.format(variant_name, pkg_name), []))
+
+    return errors
+
+
 @package_directives
 def _version_constraints_are_satisfiable_by_some_version_in_repo(pkgs, error_cls):
     """Report if version constraints used in directives are not satisfiable"""
     errors = []
     for pkg_name in pkgs:
-        pkg_cls = spack.repo.path.get_pkg_class(pkg_name)
-        filename = spack.repo.path.filename_for_package_name(pkg_name)
+        pkg_cls = spack.repo.PATH.get_pkg_class(pkg_name)
+        filename = spack.repo.PATH.filename_for_package_name(pkg_name)
         dependencies_to_check = []
         for dependency_name, dependency_data in pkg_cls.dependencies.items():
             # Skip virtual dependencies for the time being, check on
             # their versions can be added later
-            if spack.repo.path.is_virtual(dependency_name):
+            if spack.repo.PATH.is_virtual(dependency_name):
                 continue
 
             dependencies_to_check.extend([edge.spec for edge in dependency_data.values()])
@@ -729,7 +744,7 @@ def _version_constraints_are_satisfiable_by_some_version_in_repo(pkgs, error_cls
         for s in dependencies_to_check:
             dependency_pkg_cls = None
             try:
-                dependency_pkg_cls = spack.repo.path.get_pkg_class(s.name)
+                dependency_pkg_cls = spack.repo.PATH.get_pkg_class(s.name)
                 # Some packages have hacks that might cause failures on some platform
                 # Allow to explicitly set conditions to skip version checks in that case
                 skip_conditions = getattr(dependency_pkg_cls, "skip_version_audit", [])
@@ -772,7 +787,7 @@ def _analyze_variants_in_directive(pkg, constraint, directive, error_cls):
         except variant_exceptions as e:
             summary = pkg.name + ': wrong variant in "{0}" directive'
             summary = summary.format(directive)
-            filename = spack.repo.path.filename_for_package_name(pkg.name)
+            filename = spack.repo.PATH.filename_for_package_name(pkg.name)
 
             error_msg = str(e).strip()
             if isinstance(e, KeyError):

lib/spack/spack/bootstrap/config.py

@@ -124,9 +124,9 @@ def _read_and_sanitize_configuration() -> Dict[str, Any]:
 def _bootstrap_config_scopes() -> Sequence["spack.config.ConfigScope"]:
     tty.debug("[BOOTSTRAP CONFIG SCOPE] name=_builtin")
     config_scopes: MutableSequence["spack.config.ConfigScope"] = [
-        spack.config.InternalConfigScope("_builtin", spack.config.config_defaults)
+        spack.config.InternalConfigScope("_builtin", spack.config.CONFIG_DEFAULTS)
     ]
-    configuration_paths = (spack.config.configuration_defaults_path, ("bootstrap", _config_path()))
+    configuration_paths = (spack.config.CONFIGURATION_DEFAULTS_PATH, ("bootstrap", _config_path()))
     for name, path in configuration_paths:
         platform = spack.platforms.host().name
         platform_scope = spack.config.ConfigScope(

lib/spack/spack/bootstrap/core.py

@@ -476,15 +476,22 @@ def ensure_executables_in_path_or_raise(
 def _add_externals_if_missing() -> None:
     search_list = [
         # clingo
-        spack.repo.path.get_pkg_class("cmake"),
-        spack.repo.path.get_pkg_class("bison"),
+        spack.repo.PATH.get_pkg_class("cmake"),
+        spack.repo.PATH.get_pkg_class("bison"),
         # GnuPG
-        spack.repo.path.get_pkg_class("gawk"),
+        spack.repo.PATH.get_pkg_class("gawk"),
+        # develop deps
+        spack.repo.PATH.get_pkg_class("git"),
     ]
     if IS_WINDOWS:
-        search_list.append(spack.repo.path.get_pkg_class("winbison"))
-    detected_packages = spack.detection.by_executable(search_list)
-    spack.detection.update_configuration(detected_packages, scope="bootstrap")
+        search_list.append(spack.repo.PATH.get_pkg_class("winbison"))
+    externals = spack.detection.by_executable(search_list)
+    # System git is typically deprecated, so mark as non-buildable to force it as external
+    non_buildable_externals = {k: externals.pop(k) for k in ("git",) if k in externals}
+    spack.detection.update_configuration(externals, scope="bootstrap", buildable=True)
+    spack.detection.update_configuration(
+        non_buildable_externals, scope="bootstrap", buildable=False
+    )
 
 
 def clingo_root_spec() -> str:

lib/spack/spack/bootstrap/environment.py

@@ -23,6 +23,7 @@
 
 from ._common import _root_spec
 from .config import root_path, spec_for_current_python, store_path
+from .core import _add_externals_if_missing
 
 
 class BootstrapEnvironment(spack.environment.Environment):
@@ -185,6 +186,7 @@ def pytest_root_spec() -> str:
 
 def ensure_environment_dependencies() -> None:
     """Ensure Spack dependencies from the bootstrap environment are installed and ready to use"""
+    _add_externals_if_missing()
     with BootstrapEnvironment() as env:
         env.update_installations()
         env.update_syspath_and_environ()

lib/spack/spack/build_environment.py

@@ -1256,9 +1256,8 @@ def make_stack(tb, stack=None):
             func = getattr(obj, tb.tb_frame.f_code.co_name, "")
             if func:
                 typename, *_ = func.__qualname__.partition(".")
-
-            if isinstance(obj, CONTEXT_BASES) and typename not in basenames:
-                break
+                if isinstance(obj, CONTEXT_BASES) and typename not in basenames:
+                    break
     else:
         return None
 

lib/spack/spack/build_systems/autotools.py

@@ -55,7 +55,8 @@ def flags_to_build_system_args(self, flags):
         setattr(self, "configure_flag_args", [])
         for flag, values in flags.items():
             if values:
-                values_str = "{0}={1}".format(flag.upper(), " ".join(values))
+                var_name = "LIBS" if flag == "ldlibs" else flag.upper()
+                values_str = "{0}={1}".format(var_name, " ".join(values))
                 self.configure_flag_args.append(values_str)
         # Spack's fflags are meant for both F77 and FC, therefore we
         # additionaly set FCFLAGS if required.

lib/spack/spack/build_systems/cmake.py

@@ -248,7 +248,8 @@ def std_cmake_args(self):
     @staticmethod
     def std_args(pkg, generator=None):
         """Computes the standard cmake arguments for a generic package"""
-        generator = generator or "Unix Makefiles"
+        default_generator = "Ninja" if sys.platform == "win32" else "Unix Makefiles"
+        generator = generator or default_generator
         valid_primary_generators = ["Unix Makefiles", "Ninja"]
         primary_generator = _extract_primary_generator(generator)
         if primary_generator not in valid_primary_generators:

lib/spack/spack/build_systems/meson.py

@@ -209,5 +209,5 @@ def install(self, pkg, spec, prefix):
     def check(self):
         """Search Meson-generated files for the target ``test`` and run it if found."""
         with fs.working_dir(self.build_directory):
-            self._if_ninja_target_execute("test")
-            self._if_ninja_target_execute("check")
+            self.pkg._if_ninja_target_execute("test")
+            self.pkg._if_ninja_target_execute("check")

lib/spack/spack/build_systems/python.py

@@ -30,7 +30,7 @@
 
 
 class PythonExtension(spack.package_base.PackageBase):
-    maintainers("adamjstewart", "pradyunsg")
+    maintainers("adamjstewart")
 
     @property
     def import_modules(self):
@@ -201,7 +201,7 @@ def update_external_dependencies(self, extendee_spec=None):
             else:
                 python = self.get_external_python_for_prefix()
                 if not python.concrete:
-                    repo = spack.repo.path.repo_for_pkg(python)
+                    repo = spack.repo.PATH.repo_for_pkg(python)
                     python.namespace = repo.namespace
 
                     # Ensure architecture information is present
@@ -301,7 +301,7 @@ def get_external_python_for_prefix(self):
             return python_externals_configured[0]
 
         python_externals_detection = spack.detection.by_executable(
-            [spack.repo.path.get_pkg_class("python")], path_hints=[self.spec.external_path]
+            [spack.repo.PATH.get_pkg_class("python")], path_hints=[self.spec.external_path]
         )
 
         python_externals_detected = [

lib/spack/spack/build_systems/rocm.py

@@ -140,8 +140,6 @@ class ROCmPackage(PackageBase):
     depends_on("hsa-rocr-dev", when="+rocm")
     depends_on("hip +rocm", when="+rocm")
 
-    conflicts("^blt@:0.3.6", when="+rocm")
-
     # need amd gpu type for rocm builds
     conflicts("amdgpu_target=none", when="+rocm")
 

lib/spack/spack/caches.py

@@ -20,9 +20,9 @@
 
 
 def misc_cache_location():
-    """The ``misc_cache`` is Spack's cache for small data.
+    """The ``MISC_CACHE`` is Spack's cache for small data.
 
-    Currently the ``misc_cache`` stores indexes for virtual dependency
+    Currently the ``MISC_CACHE`` stores indexes for virtual dependency
     providers and for which packages provide which tags.
     """
     path = spack.config.get("config:misc_cache", spack.paths.default_misc_cache_path)
@@ -35,7 +35,7 @@ def _misc_cache():
 
 
 #: Spack's cache for small data
-misc_cache: Union[
+MISC_CACHE: Union[
     spack.util.file_cache.FileCache, llnl.util.lang.Singleton
 ] = llnl.util.lang.Singleton(_misc_cache)
 
@@ -91,6 +91,6 @@ def symlink(self, mirror_ref):
 
 
 #: Spack's local cache for downloaded source archives
-fetch_cache: Union[
+FETCH_CACHE: Union[
     spack.fetch_strategy.FsCache, llnl.util.lang.Singleton
 ] = llnl.util.lang.Singleton(_fetch_cache)

lib/spack/spack/ci.py

@@ -535,7 +535,7 @@ def __job_name(name, suffix=""):
         """Compute the name of a named job with appropriate suffix.
         Valid suffixes are either '-remove' or empty string or None
         """
-        assert type(name) == str
+        assert isinstance(name, str)
 
         jname = name
         if suffix:
@@ -885,7 +885,7 @@ def generate_gitlab_ci_yaml(
         cli_scopes = [
             os.path.relpath(s.path, concrete_env_dir)
             for s in cfg.scopes().values()
-            if type(s) == cfg.ImmutableConfigScope
+            if isinstance(s, cfg.ImmutableConfigScope)
             and s.path not in env_includes
             and os.path.exists(s.path)
         ]
@@ -1504,7 +1504,7 @@ def copy_stage_logs_to_artifacts(job_spec: spack.spec.Spec, job_log_dir: str) ->
         return
 
     try:
-        pkg_cls = spack.repo.path.get_pkg_class(job_spec.name)
+        pkg_cls = spack.repo.PATH.get_pkg_class(job_spec.name)
         job_pkg = pkg_cls(job_spec)
         tty.debug("job package: {0}".format(job_pkg))
     except AssertionError:

lib/spack/spack/cmd/__init__.py

@@ -291,7 +291,7 @@ def ensure_single_spec_or_die(spec, matching_specs):
     if len(matching_specs) <= 1:
         return
 
-    format_string = "{name}{@version}{%compiler}{arch=architecture}"
+    format_string = "{name}{@version}{%compiler.name}{@compiler.version}{arch=architecture}"
     args = ["%s matches multiple packages." % spec, "Matching packages:"]
     args += [
         colorize("  @K{%s} " % s.dag_hash(7)) + s.cformat(format_string) for s in matching_specs

lib/spack/spack/cmd/audit.py

@@ -47,7 +47,7 @@ def configs(parser, args):
 
 
 def packages(parser, args):
-    pkgs = args.name or spack.repo.path.all_package_names()
+    pkgs = args.name or spack.repo.PATH.all_package_names()
     reports = spack.audit.run_group(args.subcommand, pkgs=pkgs)
     _process_reports(reports)
 
@@ -57,7 +57,7 @@ def packages_https(parser, args):
     if not args.check_all and not args.name:
         tty.die("Please specify one or more packages to audit, or --all.")
 
-    pkgs = args.name or spack.repo.path.all_package_names()
+    pkgs = args.name or spack.repo.PATH.all_package_names()
     reports = spack.audit.run_group(args.subcommand, pkgs=pkgs)
     _process_reports(reports)
 

lib/spack/spack/cmd/blame.py

@@ -126,7 +126,7 @@ def blame(parser, args):
             blame_file = path
 
     if not blame_file:
-        pkg_cls = spack.repo.path.get_pkg_class(args.package_or_file)
+        pkg_cls = spack.repo.PATH.get_pkg_class(args.package_or_file)
         blame_file = pkg_cls.module.__file__.rstrip("c")  # .pyc -> .py
 
     # get git blame for the package

lib/spack/spack/cmd/bootstrap.py

@@ -4,6 +4,7 @@
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
 import os.path
 import shutil
+import sys
 import tempfile
 
 import llnl.util.filesystem
@@ -68,11 +69,10 @@
 
 def _add_scope_option(parser):
     scopes = spack.config.scopes()
-    scopes_metavar = spack.config.scopes_metavar
     parser.add_argument(
         "--scope",
         choices=scopes,
-        metavar=scopes_metavar,
+        metavar=spack.config.SCOPES_METAVAR,
         help="configuration scope to read/modify",
     )
 
@@ -169,7 +169,7 @@ def _reset(args):
         if not ok_to_continue:
             raise RuntimeError("Aborting")
 
-    for scope in spack.config.config.file_scopes:
+    for scope in spack.config.CONFIG.file_scopes:
         # The default scope should stay untouched
         if scope.name == "defaults":
             continue
@@ -186,7 +186,7 @@ def _reset(args):
         if os.path.exists(bootstrap_yaml):
             shutil.move(bootstrap_yaml, backup_file)
 
-        spack.config.config.clear_caches()
+        spack.config.CONFIG.clear_caches()
 
 
 def _root(args):
@@ -326,6 +326,7 @@ def _status(args):
     if missing:
         print(llnl.util.tty.color.colorize(legend))
         print()
+        sys.exit(1)
 
 
 def _add(args):

lib/spack/spack/cmd/buildcache.py

@@ -149,12 +149,11 @@ def setup_parser(subparser: argparse.ArgumentParser):
 
     # used to construct scope arguments below
     scopes = spack.config.scopes()
-    scopes_metavar = spack.config.scopes_metavar
 
     check.add_argument(
         "--scope",
         choices=scopes,
-        metavar=scopes_metavar,
+        metavar=spack.config.SCOPES_METAVAR,
         default=spack.config.default_modify_scope(),
         help="configuration scope containing mirrors to check",
     )

lib/spack/spack/cmd/checksum.py

@@ -83,7 +83,7 @@ def checksum(parser, args):
         tty.die("`spack checksum` accepts package names, not URLs.")
 
     # Get the package we're going to generate checksums for
-    pkg_cls = spack.repo.path.get_pkg_class(args.package)
+    pkg_cls = spack.repo.PATH.get_pkg_class(args.package)
     pkg = pkg_cls(spack.spec.Spec(args.package))
 
     # Build a list of versions to checksum
@@ -210,7 +210,7 @@ def add_versions_to_package(pkg: PackageBase, version_lines: str):
 
     """
     # Get filename and path for package
-    filename = spack.repo.path.filename_for_package_name(pkg.name)
+    filename = spack.repo.PATH.filename_for_package_name(pkg.name)
     num_versions_added = 0
 
     version_statement_re = re.compile(r"([\t ]+version\([^\)]*\))")

lib/spack/spack/cmd/ci.py

@@ -289,6 +289,10 @@ def ci_rebuild(args):
     rebuild_everything = os.environ.get("SPACK_REBUILD_EVERYTHING")
     require_signing = os.environ.get("SPACK_REQUIRE_SIGNING")
 
+    # If signing key was provided via "SPACK_SIGNING_KEY", then try to import it.
+    if signing_key:
+        spack_ci.import_signing_key(signing_key)
+
     # Fail early if signing is required but we don't have a signing key
     sign_binaries = require_signing is not None and require_signing.lower() == "true"
     if sign_binaries and not spack_ci.can_sign_binaries():
@@ -418,11 +422,6 @@ def ci_rebuild(args):
                 dst_file = os.path.join(repro_dir, file_name)
                 shutil.copyfile(src_file, dst_file)
 
-    # If signing key was provided via "SPACK_SIGNING_KEY", then try to
-    # import it.
-    if signing_key:
-        spack_ci.import_signing_key(signing_key)
-
     # Write this job's spec json into the reproduction directory, and it will
     # also be used in the generated "spack install" command to install the spec
     tty.debug("job concrete spec path: {0}".format(job_spec_json_path))
@@ -679,7 +678,7 @@ def ci_rebuild(args):
                 input_spec=job_spec,
                 buildcache_mirror_url=buildcache_mirror_url,
                 pipeline_mirror_url=pipeline_mirror_url,
-                sign_binaries=sign_binaries,
+                sign_binaries=spack_ci.can_sign_binaries(),
             ):
                 msg = tty.msg if result.success else tty.warn
                 msg(

lib/spack/spack/cmd/clean.py

@@ -17,6 +17,7 @@
 import spack.config
 import spack.repo
 import spack.stage
+import spack.store
 import spack.util.path
 from spack.paths import lib_path, var_path
 
@@ -117,15 +118,15 @@ def clean(parser, args):
 
     if args.downloads:
         tty.msg("Removing cached downloads")
-        spack.caches.fetch_cache.destroy()
+        spack.caches.FETCH_CACHE.destroy()
 
     if args.failures:
         tty.msg("Removing install failure marks")
-        spack.installer.clear_failures()
+        spack.store.STORE.failure_tracker.clear_all()
 
     if args.misc_cache:
         tty.msg("Removing cached information on repositories")
-        spack.caches.misc_cache.destroy()
+        spack.caches.MISC_CACHE.destroy()
 
     if args.python_cache:
         tty.msg("Removing python cache files")

lib/spack/spack/cmd/commands.py

@@ -36,13 +36,13 @@
     "bash": {
         "aliases": True,
         "format": "bash",
-        "header": os.path.join(spack.paths.share_path, "bash", "spack-completion.in"),
+        "header": os.path.join(spack.paths.share_path, "bash", "spack-completion.bash"),
         "update": os.path.join(spack.paths.share_path, "spack-completion.bash"),
     },
     "fish": {
         "aliases": True,
         "format": "fish",
-        "header": os.path.join(spack.paths.share_path, "fish", "spack-completion.in"),
+        "header": os.path.join(spack.paths.share_path, "fish", "spack-completion.fish"),
         "update": os.path.join(spack.paths.share_path, "spack-completion.fish"),
     },
 }

lib/spack/spack/cmd/compiler.py

@@ -24,7 +24,6 @@ def setup_parser(subparser):
     sp = subparser.add_subparsers(metavar="SUBCOMMAND", dest="compiler_command")
 
     scopes = spack.config.scopes()
-    scopes_metavar = spack.config.scopes_metavar
 
     # Find
     find_parser = sp.add_parser(
@@ -36,7 +35,7 @@ def setup_parser(subparser):
     find_parser.add_argument(
         "--scope",
         choices=scopes,
-        metavar=scopes_metavar,
+        metavar=spack.config.SCOPES_METAVAR,
         default=spack.config.default_modify_scope("compilers"),
         help="configuration scope to modify",
     )
@@ -50,7 +49,7 @@ def setup_parser(subparser):
     remove_parser.add_argument(
         "--scope",
         choices=scopes,
-        metavar=scopes_metavar,
+        metavar=spack.config.SCOPES_METAVAR,
         default=None,
         help="configuration scope to modify",
     )
@@ -60,7 +59,7 @@ def setup_parser(subparser):
     list_parser.add_argument(
         "--scope",
         choices=scopes,
-        metavar=scopes_metavar,
+        metavar=spack.config.SCOPES_METAVAR,
         default=spack.config.default_list_scope(),
         help="configuration scope to read from",
     )
@@ -71,7 +70,7 @@ def setup_parser(subparser):
     info_parser.add_argument(
         "--scope",
         choices=scopes,
-        metavar=scopes_metavar,
+        metavar=spack.config.SCOPES_METAVAR,
         default=spack.config.default_list_scope(),
         help="configuration scope to read from",
     )
@@ -93,7 +92,7 @@ def compiler_find(args):
         n = len(new_compilers)
         s = "s" if n > 1 else ""
 
-        config = spack.config.config
+        config = spack.config.CONFIG
         filename = config.get_config_filename(args.scope, "compilers")
         tty.msg("Added %d new compiler%s to %s" % (n, s, filename))
         colify(reversed(sorted(c.spec.display_str for c in new_compilers)), indent=4)

lib/spack/spack/cmd/compilers.py

@@ -13,12 +13,11 @@
 
 def setup_parser(subparser):
     scopes = spack.config.scopes()
-    scopes_metavar = spack.config.scopes_metavar
 
     subparser.add_argument(
         "--scope",
         choices=scopes,
-        metavar=scopes_metavar,
+        metavar=spack.config.SCOPES_METAVAR,
         help="configuration scope to read/modify",
     )
 

lib/spack/spack/cmd/config.py

@@ -27,13 +27,12 @@
 
 def setup_parser(subparser):
     scopes = spack.config.scopes()
-    scopes_metavar = spack.config.scopes_metavar
 
     # User can only choose one
     subparser.add_argument(
         "--scope",
         choices=scopes,
-        metavar=scopes_metavar,
+        metavar=spack.config.SCOPES_METAVAR,
         help="configuration scope to read/modify",
     )
 
@@ -45,7 +44,7 @@ def setup_parser(subparser):
         help="configuration section to print\n\noptions: %(choices)s",
         nargs="?",
         metavar="section",
-        choices=spack.config.section_schemas,
+        choices=spack.config.SECTION_SCHEMAS,
     )
 
     blame_parser = sp.add_parser(
@@ -55,7 +54,7 @@ def setup_parser(subparser):
         "section",
         help="configuration section to print\n\noptions: %(choices)s",
         metavar="section",
-        choices=spack.config.section_schemas,
+        choices=spack.config.SECTION_SCHEMAS,
     )
 
     edit_parser = sp.add_parser("edit", help="edit configuration file")
@@ -64,7 +63,7 @@ def setup_parser(subparser):
         help="configuration section to edit\n\noptions: %(choices)s",
         metavar="section",
         nargs="?",
-        choices=spack.config.section_schemas,
+        choices=spack.config.SECTION_SCHEMAS,
     )
     edit_parser.add_argument(
         "--print-file", action="store_true", help="print the file name that would be edited"
@@ -146,10 +145,10 @@ def config_get(args):
     scope, section = _get_scope_and_section(args)
 
     if section is not None:
-        spack.config.config.print_section(section)
+        spack.config.CONFIG.print_section(section)
 
     elif scope and scope.startswith("env:"):
-        config_file = spack.config.config.get_config_filename(scope, section)
+        config_file = spack.config.CONFIG.get_config_filename(scope, section)
         if os.path.exists(config_file):
             with open(config_file) as f:
                 print(f.read())
@@ -162,7 +161,7 @@ def config_get(args):
 
 def config_blame(args):
     """Print out line-by-line blame of merged YAML."""
-    spack.config.config.print_section(args.section, blame=True)
+    spack.config.CONFIG.print_section(args.section, blame=True)
 
 
 def config_edit(args):
@@ -181,7 +180,7 @@ def config_edit(args):
         scope, section = _get_scope_and_section(args)
         if not scope and not section:
             tty.die("`spack config edit` requires a section argument or an active environment.")
-        config_file = spack.config.config.get_config_filename(scope, section)
+        config_file = spack.config.CONFIG.get_config_filename(scope, section)
 
     if args.print_file:
         print(config_file)
@@ -194,7 +193,7 @@ def config_list(args):
 
     Used primarily for shell tab completion scripts.
     """
-    print(" ".join(list(spack.config.section_schemas)))
+    print(" ".join(list(spack.config.SECTION_SCHEMAS)))
 
 
 def config_add(args):
@@ -251,19 +250,19 @@ def _can_update_config_file(scope: spack.config.ConfigScope, cfg_file):
 
 def config_update(args):
     # Read the configuration files
-    spack.config.config.get_config(args.section, scope=args.scope)
+    spack.config.CONFIG.get_config(args.section, scope=args.scope)
     updates: List[spack.config.ConfigScope] = list(
         filter(
             lambda s: not isinstance(
                 s, (spack.config.InternalConfigScope, spack.config.ImmutableConfigScope)
             ),
-            spack.config.config.format_updates[args.section],
+            spack.config.CONFIG.format_updates[args.section],
         )
     )
 
     cannot_overwrite, skip_system_scope = [], False
     for scope in updates:
-        cfg_file = spack.config.config.get_config_filename(scope.name, args.section)
+        cfg_file = spack.config.CONFIG.get_config_filename(scope.name, args.section)
         can_be_updated = _can_update_config_file(scope, cfg_file)
         if not can_be_updated:
             if scope.name == "system":
@@ -302,7 +301,7 @@ def config_update(args):
             " the latest schema format:\n\n"
         )
         for scope in updates:
-            cfg_file = spack.config.config.get_config_filename(scope.name, args.section)
+            cfg_file = spack.config.CONFIG.get_config_filename(scope.name, args.section)
             msg += "\t[scope={0}, file={1}]\n".format(scope.name, cfg_file)
         msg += (
             "\nIf the configuration files are updated, versions of Spack "
@@ -325,7 +324,7 @@ def config_update(args):
         # Make a backup copy and rewrite the file
         bkp_file = cfg_file + ".bkp"
         shutil.copy(cfg_file, bkp_file)
-        spack.config.config.update_config(args.section, data, scope=scope.name, force=True)
+        spack.config.CONFIG.update_config(args.section, data, scope=scope.name, force=True)
         tty.msg(f'File "{cfg_file}" update [backup={bkp_file}]')
 
 
@@ -337,13 +336,13 @@ def _can_revert_update(scope_dir, cfg_file, bkp_file):
 
 
 def config_revert(args):
-    scopes = [args.scope] if args.scope else [x.name for x in spack.config.config.file_scopes]
+    scopes = [args.scope] if args.scope else [x.name for x in spack.config.CONFIG.file_scopes]
 
     # Search for backup files in the configuration scopes
     Entry = collections.namedtuple("Entry", ["scope", "cfg", "bkp"])
     to_be_restored, cannot_overwrite = [], []
     for scope in scopes:
-        cfg_file = spack.config.config.get_config_filename(scope, args.section)
+        cfg_file = spack.config.CONFIG.get_config_filename(scope, args.section)
         bkp_file = cfg_file + ".bkp"
 
         # If the backup files doesn't exist move to the next scope
@@ -457,7 +456,7 @@ def config_prefer_upstream(args):
     existing = spack.config.get("packages", scope=scope)
     new = spack.config.merge_yaml(existing, pkgs)
     spack.config.set("packages", new, scope)
-    config_file = spack.config.config.get_config_filename(scope, section)
+    config_file = spack.config.CONFIG.get_config_filename(scope, section)
 
     tty.msg("Updated config at {0}".format(config_file))
 

lib/spack/spack/cmd/create.py

@@ -915,11 +915,11 @@ def get_repository(args, name):
             )
     else:
         if spec.namespace:
-            repo = spack.repo.path.get_repo(spec.namespace, None)
+            repo = spack.repo.PATH.get_repo(spec.namespace, None)
             if not repo:
                 tty.die("Unknown namespace: '{0}'".format(spec.namespace))
         else:
-            repo = spack.repo.path.first_repo()
+            repo = spack.repo.PATH.first_repo()
 
     # Set the namespace on the spec if it's not there already
     if not spec.namespace:

lib/spack/spack/cmd/dependents.py

@@ -47,14 +47,14 @@ def inverted_dependencies():
     actual dependents.
     """
     dag = {}
-    for pkg_cls in spack.repo.path.all_package_classes():
+    for pkg_cls in spack.repo.PATH.all_package_classes():
         dag.setdefault(pkg_cls.name, set())
         for dep in pkg_cls.dependencies:
             deps = [dep]
 
             # expand virtuals if necessary
-            if spack.repo.path.is_virtual(dep):
-                deps += [s.name for s in spack.repo.path.providers_for(dep)]
+            if spack.repo.PATH.is_virtual(dep):
+                deps += [s.name for s in spack.repo.PATH.providers_for(dep)]
 
             for d in deps:
                 dag.setdefault(d, set()).add(pkg_cls.name)

lib/spack/spack/cmd/dev_build.py

@@ -98,7 +98,7 @@ def dev_build(self, args):
         tty.die("spack dev-build only takes one spec.")
 
     spec = specs[0]
-    if not spack.repo.path.exists(spec.name):
+    if not spack.repo.PATH.exists(spec.name):
         tty.die(
             "No package for '{0}' was found.".format(spec.name),
             "  Use `spack create` to create a new package",

lib/spack/spack/cmd/edit.py

@@ -31,9 +31,9 @@ def edit_package(name, repo_path, namespace):
     if repo_path:
         repo = spack.repo.Repo(repo_path)
     elif namespace:
-        repo = spack.repo.path.get_repo(namespace)
+        repo = spack.repo.PATH.get_repo(namespace)
     else:
-        repo = spack.repo.path
+        repo = spack.repo.PATH
     path = repo.filename_for_package_name(name)
 
     spec = Spec(name)

lib/spack/spack/cmd/extensions.py

@@ -58,7 +58,7 @@ def extensions(parser, args):
 
         extendable_pkgs = []
         for name in spack.repo.all_package_names():
-            pkg_cls = spack.repo.path.get_pkg_class(name)
+            pkg_cls = spack.repo.PATH.get_pkg_class(name)
             if pkg_cls.extendable:
                 extendable_pkgs.append(name)
 
@@ -81,7 +81,7 @@ def extensions(parser, args):
 
     if args.show in ("packages", "all"):
         # List package names of extensions
-        extensions = spack.repo.path.extensions_for(spec)
+        extensions = spack.repo.PATH.extensions_for(spec)
         if not extensions:
             tty.msg("%s has no extensions." % spec.cshort_spec)
         else:

lib/spack/spack/cmd/external.py

@@ -13,6 +13,7 @@
 import spack
 import spack.cmd
 import spack.cmd.common.arguments
+import spack.config
 import spack.cray_manifest as cray_manifest
 import spack.detection
 import spack.error
@@ -27,7 +28,6 @@ def setup_parser(subparser):
     sp = subparser.add_subparsers(metavar="SUBCOMMAND", dest="external_command")
 
     scopes = spack.config.scopes()
-    scopes_metavar = spack.config.scopes_metavar
 
     find_parser = sp.add_parser("find", help="add external packages to packages.yaml")
     find_parser.add_argument(
@@ -47,7 +47,7 @@ def setup_parser(subparser):
     find_parser.add_argument(
         "--scope",
         choices=scopes,
-        metavar=scopes_metavar,
+        metavar=spack.config.SCOPES_METAVAR,
         default=spack.config.default_modify_scope("packages"),
         help="configuration scope to modify",
     )
@@ -133,9 +133,9 @@ def external_find(args):
 
     # Add the packages that have been required explicitly
     if args.packages:
-        pkg_cls_to_check = [spack.repo.path.get_pkg_class(pkg) for pkg in args.packages]
+        pkg_cls_to_check = [spack.repo.PATH.get_pkg_class(pkg) for pkg in args.packages]
         if args.tags:
-            allowed = set(spack.repo.path.packages_with_tags(*args.tags))
+            allowed = set(spack.repo.PATH.packages_with_tags(*args.tags))
             pkg_cls_to_check = [x for x in pkg_cls_to_check if x.name in allowed]
 
     if args.tags and not pkg_cls_to_check:
@@ -144,15 +144,15 @@ def external_find(args):
         # Since tags are cached it's much faster to construct what we need
         # to search directly, rather than filtering after the fact
         pkg_cls_to_check = [
-            spack.repo.path.get_pkg_class(pkg_name)
+            spack.repo.PATH.get_pkg_class(pkg_name)
             for tag in args.tags
-            for pkg_name in spack.repo.path.packages_with_tags(tag)
+            for pkg_name in spack.repo.PATH.packages_with_tags(tag)
         ]
         pkg_cls_to_check = list(set(pkg_cls_to_check))
 
     # If the list of packages is empty, search for every possible package
     if not args.tags and not pkg_cls_to_check:
-        pkg_cls_to_check = list(spack.repo.path.all_package_classes())
+        pkg_cls_to_check = list(spack.repo.PATH.all_package_classes())
 
     # If the user specified any packages to exclude from external find, add them here
     if args.exclude:
@@ -165,7 +165,7 @@ def external_find(args):
         detected_packages, scope=args.scope, buildable=not args.not_buildable
     )
     if new_entries:
-        path = spack.config.config.get_config_filename(args.scope, "packages")
+        path = spack.config.CONFIG.get_config_filename(args.scope, "packages")
         msg = "The following specs have been detected on this system and added to {0}"
         tty.msg(msg.format(path))
         spack.cmd.display_specs(new_entries)
@@ -239,7 +239,7 @@ def _collect_and_consume_cray_manifest_files(
 
 def external_list(args):
     # Trigger a read of all packages, might take a long time.
-    list(spack.repo.path.all_package_classes())
+    list(spack.repo.PATH.all_package_classes())
     # Print all the detectable packages
     tty.msg("Detectable packages per repository")
     for namespace, pkgs in sorted(spack.package_base.detectable_packages.items()):

lib/spack/spack/cmd/find.py

@@ -268,7 +268,7 @@ def find(parser, args):
 
     # If tags have been specified on the command line, filter by tags
     if args.tags:
-        packages_with_tags = spack.repo.path.packages_with_tags(*args.tags)
+        packages_with_tags = spack.repo.PATH.packages_with_tags(*args.tags)
         results = [x for x in results if x.name in packages_with_tags]
 
     if args.loaded:

lib/spack/spack/cmd/info.py

@@ -349,7 +349,7 @@ def print_virtuals(pkg):
 
 def info(parser, args):
     spec = spack.spec.Spec(args.package)
-    pkg_cls = spack.repo.path.get_pkg_class(spec.name)
+    pkg_cls = spack.repo.PATH.get_pkg_class(spec.name)
     pkg = pkg_cls(spec)
 
     # Output core package information

lib/spack/spack/cmd/list.py

@@ -107,7 +107,7 @@ def match(p, f):
                 if f.match(p):
                     return True
 
-                pkg_cls = spack.repo.path.get_pkg_class(p)
+                pkg_cls = spack.repo.PATH.get_pkg_class(p)
                 if pkg_cls.__doc__:
                     return f.match(pkg_cls.__doc__)
                 return False
@@ -159,7 +159,7 @@ def get_dependencies(pkg):
 @formatter
 def version_json(pkg_names, out):
     """Print all packages with their latest versions."""
-    pkg_classes = [spack.repo.path.get_pkg_class(name) for name in pkg_names]
+    pkg_classes = [spack.repo.PATH.get_pkg_class(name) for name in pkg_names]
 
     out.write("[\n")
 
@@ -201,7 +201,7 @@ def html(pkg_names, out):
     """
 
     # Read in all packages
-    pkg_classes = [spack.repo.path.get_pkg_class(name) for name in pkg_names]
+    pkg_classes = [spack.repo.PATH.get_pkg_class(name) for name in pkg_names]
 
     # Start at 2 because the title of the page from Sphinx is id1.
     span_id = 2
@@ -313,13 +313,13 @@ def list(parser, args):
 
     # If tags have been specified on the command line, filter by tags
     if args.tags:
-        packages_with_tags = spack.repo.path.packages_with_tags(*args.tags)
+        packages_with_tags = spack.repo.PATH.packages_with_tags(*args.tags)
         sorted_packages = [p for p in sorted_packages if p in packages_with_tags]
 
     if args.update:
         # change output stream if user asked for update
         if os.path.exists(args.update):
-            if os.path.getmtime(args.update) > spack.repo.path.last_mtime():
+            if os.path.getmtime(args.update) > spack.repo.PATH.last_mtime():
                 tty.msg("File is up to date: %s" % args.update)
                 return
 

lib/spack/spack/cmd/location.py

@@ -109,7 +109,7 @@ def location(parser, args):
         return
 
     if args.packages:
-        print(spack.repo.path.first_repo().root)
+        print(spack.repo.PATH.first_repo().root)
         return
 
     if args.stages:
@@ -135,7 +135,7 @@ def location(parser, args):
 
     # Package dir just needs the spec name
     if args.package_dir:
-        print(spack.repo.path.dirname_for_package_name(spec.name))
+        print(spack.repo.PATH.dirname_for_package_name(spec.name))
         return
 
     # Either concretize or filter from already concretized environment

lib/spack/spack/cmd/maintainers.py

@@ -54,11 +54,11 @@ def setup_parser(subparser):
 
 def packages_to_maintainers(package_names=None):
     if not package_names:
-        package_names = spack.repo.path.all_package_names()
+        package_names = spack.repo.PATH.all_package_names()
 
     pkg_to_users = defaultdict(lambda: set())
     for name in package_names:
-        cls = spack.repo.path.get_pkg_class(name)
+        cls = spack.repo.PATH.get_pkg_class(name)
         for user in cls.maintainers:
             pkg_to_users[name].add(user)
 
@@ -67,8 +67,8 @@ def packages_to_maintainers(package_names=None):
 
 def maintainers_to_packages(users=None):
     user_to_pkgs = defaultdict(lambda: [])
-    for name in spack.repo.path.all_package_names():
-        cls = spack.repo.path.get_pkg_class(name)
+    for name in spack.repo.PATH.all_package_names():
+        cls = spack.repo.PATH.get_pkg_class(name)
         for user in cls.maintainers:
             lower_users = [u.lower() for u in users]
             if not users or user.lower() in lower_users:
@@ -80,8 +80,8 @@ def maintainers_to_packages(users=None):
 def maintained_packages():
     maintained = []
     unmaintained = []
-    for name in spack.repo.path.all_package_names():
-        cls = spack.repo.path.get_pkg_class(name)
+    for name in spack.repo.PATH.all_package_names():
+        cls = spack.repo.PATH.get_pkg_class(name)
         if cls.maintainers:
             maintained.append(name)
         else:

lib/spack/spack/cmd/mirror.py

@@ -90,7 +90,6 @@ def setup_parser(subparser):
 
     # used to construct scope arguments below
     scopes = spack.config.scopes()
-    scopes_metavar = spack.config.scopes_metavar
 
     # Add
     add_parser = sp.add_parser("add", help=mirror_add.__doc__)
@@ -99,7 +98,7 @@ def setup_parser(subparser):
     add_parser.add_argument(
         "--scope",
         choices=scopes,
-        metavar=scopes_metavar,
+        metavar=spack.config.SCOPES_METAVAR,
         default=spack.config.default_modify_scope(),
         help="configuration scope to modify",
     )
@@ -119,7 +118,7 @@ def setup_parser(subparser):
     remove_parser.add_argument(
         "--scope",
         choices=scopes,
-        metavar=scopes_metavar,
+        metavar=spack.config.SCOPES_METAVAR,
         default=spack.config.default_modify_scope(),
         help="configuration scope to modify",
     )
@@ -138,7 +137,7 @@ def setup_parser(subparser):
     set_url_parser.add_argument(
         "--scope",
         choices=scopes,
-        metavar=scopes_metavar,
+        metavar=spack.config.SCOPES_METAVAR,
         default=spack.config.default_modify_scope(),
         help="configuration scope to modify",
     )
@@ -167,7 +166,7 @@ def setup_parser(subparser):
     set_parser.add_argument(
         "--scope",
         choices=scopes,
-        metavar=scopes_metavar,
+        metavar=spack.config.SCOPES_METAVAR,
         default=spack.config.default_modify_scope(),
         help="configuration scope to modify",
     )
@@ -178,7 +177,7 @@ def setup_parser(subparser):
     list_parser.add_argument(
         "--scope",
         choices=scopes,
-        metavar=scopes_metavar,
+        metavar=spack.config.SCOPES_METAVAR,
         default=spack.config.default_list_scope(),
         help="configuration scope to read from",
     )
@@ -444,7 +443,7 @@ def mirror_create(args):
         )
 
     # When no directory is provided, the source dir is used
-    path = args.directory or spack.caches.fetch_cache_location()
+    path = args.directory or spack.caches.FETCH_CACHE_location()
 
     if args.all and not ev.active_environment():
         create_mirror_for_all_specs(
@@ -474,7 +473,7 @@ def create_mirror_for_all_specs(path, skip_unstable_versions, selection_fn):
         path, skip_unstable_versions=skip_unstable_versions
     )
     for candidate in mirror_specs:
-        pkg_cls = spack.repo.path.get_pkg_class(candidate.name)
+        pkg_cls = spack.repo.PATH.get_pkg_class(candidate.name)
         pkg_obj = pkg_cls(spack.spec.Spec(candidate))
         mirror_stats.next_spec(pkg_obj.spec)
         spack.mirror.create_mirror_from_package_object(pkg_obj, mirror_cache, mirror_stats)

lib/spack/spack/cmd/modules/__init__.py

@@ -309,7 +309,7 @@ def refresh(module_type, specs, args):
 
     # Skip unknown packages.
     writers = [
-        cls(spec, args.module_set_name) for spec in specs if spack.repo.path.exists(spec.name)
+        cls(spec, args.module_set_name) for spec in specs if spack.repo.PATH.exists(spec.name)
     ]
 
     # Filter excluded packages early
@@ -321,12 +321,13 @@ def refresh(module_type, specs, args):
         file2writer[item.layout.filename].append(item)
 
     if len(file2writer) != len(writers):
+        spec_fmt_str = "{name}@={version}%{compiler}/{hash:7} {variants} arch={arch}"
         message = "Name clashes detected in module files:\n"
         for filename, writer_list in file2writer.items():
             if len(writer_list) > 1:
                 message += "\nfile: {0}\n".format(filename)
                 for x in writer_list:
-                    message += "spec: {0}\n".format(x.spec.format())
+                    message += "spec: {0}\n".format(x.spec.format(spec_fmt_str))
         tty.error(message)
         tty.error("Operation aborted")
         raise SystemExit(1)
@@ -376,7 +377,7 @@ def refresh(module_type, specs, args):
 def modules_cmd(parser, args, module_type, callbacks=callbacks):
     # Qualifiers to be used when querying the db for specs
     constraint_qualifiers = {
-        "refresh": {"installed": True, "known": lambda x: not spack.repo.path.exists(x)}
+        "refresh": {"installed": True, "known": lambda x: not spack.repo.PATH.exists(x)}
     }
     query_args = constraint_qualifiers.get(args.subparser_name, {})
 

lib/spack/spack/cmd/pkg.py

@@ -143,7 +143,7 @@ def pkg_source(args):
         tty.die("spack pkg source requires exactly one spec")
 
     spec = specs[0]
-    filename = spack.repo.path.filename_for_package_name(spec.name)
+    filename = spack.repo.PATH.filename_for_package_name(spec.name)
 
     # regular source dump -- just get the package and print its contents
     if args.canonical:
@@ -184,7 +184,7 @@ def pkg_grep(args, unknown_args):
     grouper = lambda e: e[0] // 500
 
     # set up iterator and save the first group to ensure we don't end up with a group of size 1
-    groups = itertools.groupby(enumerate(spack.repo.path.all_package_paths()), grouper)
+    groups = itertools.groupby(enumerate(spack.repo.PATH.all_package_paths()), grouper)
     if not groups:
         return 0  # no packages to search
 

lib/spack/spack/cmd/providers.py

@@ -24,7 +24,7 @@ def setup_parser(subparser):
 
 
 def providers(parser, args):
-    valid_virtuals = sorted(spack.repo.path.provider_index.providers.keys())
+    valid_virtuals = sorted(spack.repo.PATH.provider_index.providers.keys())
 
     buffer = io.StringIO()
     isatty = sys.stdout.isatty()
@@ -53,5 +53,5 @@ def providers(parser, args):
     for spec in specs:
         if sys.stdout.isatty():
             print("{0}:".format(spec))
-        spack.cmd.display_specs(sorted(spack.repo.path.providers_for(spec)))
+        spack.cmd.display_specs(sorted(spack.repo.PATH.providers_for(spec)))
         print("")

lib/spack/spack/cmd/repo.py

@@ -20,7 +20,6 @@
 def setup_parser(subparser):
     sp = subparser.add_subparsers(metavar="SUBCOMMAND", dest="repo_command")
     scopes = spack.config.scopes()
-    scopes_metavar = spack.config.scopes_metavar
 
     # Create
     create_parser = sp.add_parser("create", help=repo_create.__doc__)
@@ -45,7 +44,7 @@ def setup_parser(subparser):
     list_parser.add_argument(
         "--scope",
         choices=scopes,
-        metavar=scopes_metavar,
+        metavar=spack.config.SCOPES_METAVAR,
         default=spack.config.default_list_scope(),
         help="configuration scope to read from",
     )
@@ -56,7 +55,7 @@ def setup_parser(subparser):
     add_parser.add_argument(
         "--scope",
         choices=scopes,
-        metavar=scopes_metavar,
+        metavar=spack.config.SCOPES_METAVAR,
         default=spack.config.default_modify_scope(),
         help="configuration scope to modify",
     )
@@ -69,7 +68,7 @@ def setup_parser(subparser):
     remove_parser.add_argument(
         "--scope",
         choices=scopes,
-        metavar=scopes_metavar,
+        metavar=spack.config.SCOPES_METAVAR,
         default=spack.config.default_modify_scope(),
         help="configuration scope to modify",
     )

lib/spack/spack/cmd/resource.py

@@ -29,7 +29,7 @@ def setup_parser(subparser):
 
 def _show_patch(sha256):
     """Show a record from the patch index."""
-    patches = spack.repo.path.patch_index.index
+    patches = spack.repo.PATH.patch_index.index
     data = patches.get(sha256)
 
     if not data:
@@ -47,7 +47,7 @@ def _show_patch(sha256):
         owner = rec["owner"]
 
         if "relative_path" in rec:
-            pkg_dir = spack.repo.path.get_pkg_class(owner).package_dir
+            pkg_dir = spack.repo.PATH.get_pkg_class(owner).package_dir
             path = os.path.join(pkg_dir, rec["relative_path"])
             print("    path:       %s" % path)
         else:
@@ -60,7 +60,7 @@ def _show_patch(sha256):
 
 def resource_list(args):
     """list all resources known to spack (currently just patches)"""
-    patches = spack.repo.path.patch_index.index
+    patches = spack.repo.PATH.patch_index.index
     for sha256 in patches:
         if args.only_hashes:
             print(sha256)

lib/spack/spack/cmd/tags.py

@@ -68,7 +68,7 @@ def tags(parser, args):
         return
 
     # unique list of available tags
-    available_tags = sorted(spack.repo.path.tag_index.keys())
+    available_tags = sorted(spack.repo.PATH.tag_index.keys())
     if not available_tags:
         tty.msg("No tagged packages")
         return

lib/spack/spack/cmd/test.py

@@ -228,7 +228,7 @@ def create_reporter(args, specs_to_test, test_suite):
 
 def test_list(args):
     """list installed packages with available tests"""
-    tagged = set(spack.repo.path.packages_with_tags(*args.tag)) if args.tag else set()
+    tagged = set(spack.repo.PATH.packages_with_tags(*args.tag)) if args.tag else set()
 
     def has_test_and_tags(pkg_class):
         tests = spack.install_test.test_functions(pkg_class)
@@ -237,7 +237,7 @@ def has_test_and_tags(pkg_class):
     if args.list_all:
         report_packages = [
             pkg_class.name
-            for pkg_class in spack.repo.path.all_package_classes()
+            for pkg_class in spack.repo.PATH.all_package_classes()
             if has_test_and_tags(pkg_class)
         ]
 

lib/spack/spack/cmd/unit_test.py

@@ -209,12 +209,11 @@ def unit_test(parser, args, unknown_args):
     # mock configuration used by unit tests
     # Note: skip on windows here because for the moment,
     # clingo is wholly unsupported from bootstrap
-    if sys.platform != "win32":
-        with spack.bootstrap.ensure_bootstrap_configuration():
-            spack.bootstrap.ensure_core_dependencies()
-            if pytest is None:
-                spack.bootstrap.ensure_environment_dependencies()
-                import pytest
+    with spack.bootstrap.ensure_bootstrap_configuration():
+        spack.bootstrap.ensure_core_dependencies()
+        if pytest is None:
+            spack.bootstrap.ensure_environment_dependencies()
+            import pytest
 
     if args.pytest_help:
         # make the pytest.main help output more accurate

lib/spack/spack/cmd/url.py

@@ -155,7 +155,7 @@ def url_list(args):
     urls = set()
 
     # Gather set of URLs from all packages
-    for pkg_cls in spack.repo.path.all_package_classes():
+    for pkg_cls in spack.repo.PATH.all_package_classes():
         url = getattr(pkg_cls, "url", None)
         urls = url_list_parsing(args, urls, url, pkg_cls)
 
@@ -192,7 +192,7 @@ def url_summary(args):
     tty.msg("Generating a summary of URL parsing in Spack...")
 
     # Loop through all packages
-    for pkg_cls in spack.repo.path.all_package_classes():
+    for pkg_cls in spack.repo.PATH.all_package_classes():
         urls = set()
         pkg = pkg_cls(spack.spec.Spec(pkg_cls.name))
 
@@ -336,7 +336,7 @@ def add(self, pkg_name, fetcher):
     version_stats = UrlStats()
     resource_stats = UrlStats()
 
-    for pkg_cls in spack.repo.path.all_package_classes():
+    for pkg_cls in spack.repo.PATH.all_package_classes():
         npkgs += 1
 
         for v in pkg_cls.versions:

lib/spack/spack/cmd/versions.py

@@ -45,7 +45,7 @@ def setup_parser(subparser):
 
 def versions(parser, args):
     spec = spack.spec.Spec(args.package)
-    pkg_cls = spack.repo.path.get_pkg_class(spec.name)
+    pkg_cls = spack.repo.PATH.get_pkg_class(spec.name)
     pkg = pkg_cls(spec)
 
     safe_versions = pkg.versions

lib/spack/spack/compilers/__init__.py

@@ -135,7 +135,7 @@ def _init_compiler_config(*, scope):
 
 def compiler_config_files():
     config_files = list()
-    config = spack.config.config
+    config = spack.config.CONFIG
     for scope in config.file_scopes:
         name = scope.name
         compiler_config = config.get("compilers", scope=name)
@@ -169,7 +169,7 @@ def remove_compiler_from_config(compiler_spec, scope=None):
     """
     candidate_scopes = [scope]
     if scope is None:
-        candidate_scopes = spack.config.config.scopes.keys()
+        candidate_scopes = spack.config.CONFIG.scopes.keys()
 
     removal_happened = False
     for current_scope in candidate_scopes:
@@ -523,7 +523,7 @@ def compiler_for_spec(compiler_spec, arch_spec):
 
 @_auto_compiler_spec
 def get_compiler_duplicates(compiler_spec, arch_spec):
-    config = spack.config.config
+    config = spack.config.CONFIG
 
     scope_to_compilers = {}
     for scope in config.scopes:

lib/spack/spack/concretize.py

@@ -28,6 +28,7 @@
 
 import spack.abi
 import spack.compilers
+import spack.config
 import spack.environment
 import spack.error
 import spack.platforms
@@ -37,7 +38,6 @@
 import spack.tengine
 import spack.util.path
 import spack.variant as vt
-from spack.config import config
 from spack.package_prefs import PackagePrefs, is_spec_buildable, spec_externals
 from spack.version import ClosedOpenRange, VersionList, ver
 
@@ -76,7 +76,7 @@ class Concretizer:
 
     def __init__(self, abstract_spec=None):
         if Concretizer.check_for_compiler_existence is None:
-            Concretizer.check_for_compiler_existence = not config.get(
+            Concretizer.check_for_compiler_existence = not spack.config.get(
                 "config:install_missing_compilers", False
             )
         self.abstract_spec = abstract_spec
@@ -113,7 +113,7 @@ def _valid_virtuals_and_externals(self, spec):
         pref_key = lambda spec: 0  # no-op pref key
 
         if spec.virtual:
-            candidates = spack.repo.path.providers_for(spec)
+            candidates = spack.repo.PATH.providers_for(spec)
             if not candidates:
                 raise spack.error.UnsatisfiableProviderSpecError(candidates[0], spec)
 

lib/spack/spack/config.py

@@ -47,6 +47,8 @@
 import spack.platforms
 import spack.schema
 import spack.schema.bootstrap
+import spack.schema.cdash
+import spack.schema.ci
 import spack.schema.compilers
 import spack.schema.concretizer
 import spack.schema.config
@@ -64,7 +66,7 @@
 from spack.util.cpus import cpus_available
 
 #: Dict from section names -> schema for that section
-section_schemas = {
+SECTION_SCHEMAS = {
     "compilers": spack.schema.compilers.schema,
     "concretizer": spack.schema.concretizer.schema,
     "mirrors": spack.schema.mirrors.schema,
@@ -80,16 +82,16 @@
 
 # Same as above, but including keys for environments
 # this allows us to unify config reading between configs and environments
-all_schemas = copy.deepcopy(section_schemas)
-all_schemas.update({spack.schema.env.TOP_LEVEL_KEY: spack.schema.env.schema})
+_ALL_SCHEMAS = copy.deepcopy(SECTION_SCHEMAS)
+_ALL_SCHEMAS.update({spack.schema.env.TOP_LEVEL_KEY: spack.schema.env.schema})
 
 #: Path to the default configuration
-configuration_defaults_path = ("defaults", os.path.join(spack.paths.etc_path, "defaults"))
+CONFIGURATION_DEFAULTS_PATH = ("defaults", os.path.join(spack.paths.etc_path, "defaults"))
 
 #: Hard-coded default values for some key configuration options.
 #: This ensures that Spack will still work even if config.yaml in
 #: the defaults scope is removed.
-config_defaults = {
+CONFIG_DEFAULTS = {
     "config": {
         "debug": False,
         "connect_timeout": 10,
@@ -105,10 +107,10 @@
 
 #: metavar to use for commands that accept scopes
 #: this is shorter and more readable than listing all choices
-scopes_metavar = "{defaults,system,site,user}[/PLATFORM] or env:ENVIRONMENT"
+SCOPES_METAVAR = "{defaults,system,site,user}[/PLATFORM] or env:ENVIRONMENT"
 
 #: Base name for the (internal) overrides scope.
-overrides_base_name = "overrides-"
+_OVERRIDES_BASE_NAME = "overrides-"
 
 
 class ConfigScope:
@@ -134,7 +136,7 @@ def get_section_filename(self, section):
     def get_section(self, section):
         if section not in self.sections:
             path = self.get_section_filename(section)
-            schema = section_schemas[section]
+            schema = SECTION_SCHEMAS[section]
             data = read_config_file(path, schema)
             self.sections[section] = data
         return self.sections[section]
@@ -145,7 +147,7 @@ def _write_section(self, section):
 
         # We copy data here to avoid adding defaults at write time
         validate_data = copy.deepcopy(data)
-        validate(validate_data, section_schemas[section])
+        validate(validate_data, SECTION_SCHEMAS[section])
 
         try:
             mkdirp(self.path)
@@ -317,7 +319,7 @@ def __init__(self, name, data=None):
             data = InternalConfigScope._process_dict_keyname_overrides(data)
             for section in data:
                 dsec = data[section]
-                validate({section: dsec}, section_schemas[section])
+                validate({section: dsec}, SECTION_SCHEMAS[section])
                 self.sections[section] = _mark_internal(syaml.syaml_dict({section: dsec}), name)
 
     def get_section_filename(self, section):
@@ -333,7 +335,7 @@ def _write_section(self, section):
         """This only validates, as the data is already in memory."""
         data = self.get_section(section)
         if data is not None:
-            validate(data, section_schemas[section])
+            validate(data, SECTION_SCHEMAS[section])
         self.sections[section] = _mark_internal(data, self.name)
 
     def __repr__(self):
@@ -430,7 +432,7 @@ def file_scopes(self) -> List[ConfigScope]:
         return [
             s
             for s in self.scopes.values()
-            if (type(s) == ConfigScope or type(s) == SingleFileScope)
+            if (type(s) is ConfigScope or type(s) is SingleFileScope)
         ]
 
     def highest_precedence_scope(self) -> ConfigScope:
@@ -711,11 +713,11 @@ def override(path_or_scope, value=None):
     """
     if isinstance(path_or_scope, ConfigScope):
         overrides = path_or_scope
-        config.push_scope(path_or_scope)
+        CONFIG.push_scope(path_or_scope)
     else:
-        base_name = overrides_base_name
+        base_name = _OVERRIDES_BASE_NAME
         # Ensure the new override gets a unique scope name
-        current_overrides = [s.name for s in config.matching_scopes(r"^{0}".format(base_name))]
+        current_overrides = [s.name for s in CONFIG.matching_scopes(r"^{0}".format(base_name))]
         num_overrides = len(current_overrides)
         while True:
             scope_name = "{0}{1}".format(base_name, num_overrides)
@@ -725,19 +727,19 @@ def override(path_or_scope, value=None):
                 break
 
         overrides = InternalConfigScope(scope_name)
-        config.push_scope(overrides)
-        config.set(path_or_scope, value, scope=scope_name)
+        CONFIG.push_scope(overrides)
+        CONFIG.set(path_or_scope, value, scope=scope_name)
 
     try:
-        yield config
+        yield CONFIG
     finally:
-        scope = config.remove_scope(overrides.name)
+        scope = CONFIG.remove_scope(overrides.name)
         assert scope is overrides
 
 
 #: configuration scopes added on the command line
 #: set by ``spack.main.main()``.
-command_line_scopes: List[str] = []
+COMMAND_LINE_SCOPES: List[str] = []
 
 
 def _add_platform_scope(cfg, scope_type, name, path):
@@ -781,14 +783,14 @@ def create():
     cfg = Configuration()
 
     # first do the builtin, hardcoded defaults
-    builtin = InternalConfigScope("_builtin", config_defaults)
+    builtin = InternalConfigScope("_builtin", CONFIG_DEFAULTS)
     cfg.push_scope(builtin)
 
     # Builtin paths to configuration files in Spack
     configuration_paths = [
         # Default configuration scope is the lowest-level scope. These are
         # versioned with Spack and can be overridden by systems, sites or users
-        configuration_defaults_path
+        CONFIGURATION_DEFAULTS_PATH
     ]
 
     disable_local_config = "SPACK_DISABLE_LOCAL_CONFIG" in os.environ
@@ -815,7 +817,7 @@ def create():
         _add_platform_scope(cfg, ConfigScope, name, path)
 
     # add command-line scopes
-    _add_command_line_scopes(cfg, command_line_scopes)
+    _add_command_line_scopes(cfg, COMMAND_LINE_SCOPES)
 
     # we make a special scope for spack commands so that they can
     # override configuration options.
@@ -825,7 +827,7 @@ def create():
 
 
 #: This is the singleton configuration instance for Spack.
-config: Union[Configuration, llnl.util.lang.Singleton] = llnl.util.lang.Singleton(create)
+CONFIG: Union[Configuration, llnl.util.lang.Singleton] = llnl.util.lang.Singleton(create)
 
 
 def add_from_file(filename, scope=None):
@@ -838,7 +840,7 @@ def add_from_file(filename, scope=None):
     # update all sections from config dict
     # We have to iterate on keys to keep overrides from the file
     for section in data.keys():
-        if section in section_schemas.keys():
+        if section in SECTION_SCHEMAS.keys():
             # Special handling for compiler scope difference
             # Has to be handled after we choose a section
             if scope is None:
@@ -849,7 +851,7 @@ def add_from_file(filename, scope=None):
             new = merge_yaml(existing, value)
 
             # We cannot call config.set directly (set is a type)
-            config.set(section, new, scope)
+            CONFIG.set(section, new, scope)
 
 
 def add(fullpath, scope=None):
@@ -897,12 +899,12 @@ def add(fullpath, scope=None):
 
     # merge value into existing
     new = merge_yaml(existing, value)
-    config.set(path, new, scope)
+    CONFIG.set(path, new, scope)
 
 
 def get(path, default=None, scope=None):
     """Module-level wrapper for ``Configuration.get()``."""
-    return config.get(path, default, scope)
+    return CONFIG.get(path, default, scope)
 
 
 def set(path, value, scope=None):
@@ -910,26 +912,26 @@ def set(path, value, scope=None):
 
     Accepts the path syntax described in ``get()``.
     """
-    return config.set(path, value, scope)
+    return CONFIG.set(path, value, scope)
 
 
 def add_default_platform_scope(platform):
     plat_name = os.path.join("defaults", platform)
-    plat_path = os.path.join(configuration_defaults_path[1], platform)
-    config.push_scope(ConfigScope(plat_name, plat_path))
+    plat_path = os.path.join(CONFIGURATION_DEFAULTS_PATH[1], platform)
+    CONFIG.push_scope(ConfigScope(plat_name, plat_path))
 
 
 def scopes():
     """Convenience function to get list of configuration scopes."""
-    return config.scopes
+    return CONFIG.scopes
 
 
 def _validate_section_name(section):
     """Exit if the section is not a valid section."""
-    if section not in section_schemas:
+    if section not in SECTION_SCHEMAS:
         raise ConfigSectionError(
             "Invalid config section: '%s'. Options are: %s"
-            % (section, " ".join(section_schemas.keys()))
+            % (section, " ".join(SECTION_SCHEMAS.keys()))
         )
 
 
@@ -990,7 +992,7 @@ def read_config_file(filename, schema=None):
         if data:
             if not schema:
                 key = next(iter(data))
-                schema = all_schemas[key]
+                schema = _ALL_SCHEMAS[key]
             validate(data, schema)
         return data
 
@@ -1089,7 +1091,7 @@ def get_valid_type(path):
         test_data = {component: test_data}
 
     try:
-        validate(test_data, section_schemas[section])
+        validate(test_data, SECTION_SCHEMAS[section])
     except (ConfigFormatError, AttributeError) as e:
         jsonschema_error = e.validation_error
         if jsonschema_error.validator == "type":
@@ -1278,9 +1280,9 @@ def default_modify_scope(section="config"):
             If this is not 'compilers', a general (non-platform) scope is used.
     """
     if section == "compilers":
-        return spack.config.config.highest_precedence_scope().name
+        return CONFIG.highest_precedence_scope().name
     else:
-        return spack.config.config.highest_precedence_non_platform_scope().name
+        return CONFIG.highest_precedence_non_platform_scope().name
 
 
 def default_list_scope():
@@ -1337,18 +1339,18 @@ def use_configuration(*scopes_or_paths):
     Returns:
         Configuration object associated with the scopes passed as arguments
     """
-    global config
+    global CONFIG
 
     # Normalize input and construct a Configuration object
     configuration = _config_from(scopes_or_paths)
-    config.clear_caches(), configuration.clear_caches()
+    CONFIG.clear_caches(), configuration.clear_caches()
 
-    saved_config, config = config, configuration
+    saved_config, CONFIG = CONFIG, configuration
 
     try:
         yield configuration
     finally:
-        config = saved_config
+        CONFIG = saved_config
 
 
 @llnl.util.lang.memoized

lib/spack/spack/container/writers/__init__.py

@@ -5,8 +5,8 @@
 """Writers for different kind of recipes and related
 convenience functions.
 """
-import collections
 import copy
+from collections import namedtuple
 from typing import Optional
 
 import spack.environment as ev
@@ -159,13 +159,13 @@ def depfile(self):
     @tengine.context_property
     def run(self):
         """Information related to the run image."""
-        Run = collections.namedtuple("Run", ["image"])
+        Run = namedtuple("Run", ["image"])
         return Run(image=self.final_image)
 
     @tengine.context_property
     def build(self):
         """Information related to the build image."""
-        Build = collections.namedtuple("Build", ["image"])
+        Build = namedtuple("Build", ["image"])
         return Build(image=self.build_image)
 
     @tengine.context_property
@@ -176,12 +176,13 @@ def strip(self):
     @tengine.context_property
     def paths(self):
         """Important paths in the image"""
-        Paths = collections.namedtuple("Paths", ["environment", "store", "hidden_view", "view"])
+        Paths = namedtuple("Paths", ["environment", "store", "view_parent", "view", "former_view"])
         return Paths(
             environment="/opt/spack-environment",
             store="/opt/software",
-            hidden_view="/opt/._view",
-            view="/opt/view",
+            view_parent="/opt/views",
+            view="/opt/views/view",
+            former_view="/opt/view",  # /opt/view -> /opt/views/view for backward compatibility
         )
 
     @tengine.context_property
@@ -257,7 +258,7 @@ def _package_info_from(self, package_list):
 
         update, install, clean = commands_for(os_pkg_manager)
 
-        Packages = collections.namedtuple("Packages", ["update", "install", "list", "clean"])
+        Packages = namedtuple("Packages", ["update", "install", "list", "clean"])
         return Packages(update=update, install=install, list=package_list, clean=clean)
 
     def _os_pkg_manager(self):
@@ -273,7 +274,7 @@ def _os_pkg_manager(self):
 
     @tengine.context_property
     def extra_instructions(self):
-        Extras = collections.namedtuple("Extra", ["build", "final"])
+        Extras = namedtuple("Extra", ["build", "final"])
         extras = self.container_config.get("extra_instructions", {})
         build, final = extras.get("build", None), extras.get("final", None)
         return Extras(build=build, final=final)
@@ -295,7 +296,7 @@ def bootstrap(self):
             context = {"bootstrap": {"image": self.bootstrap_image, "spack_checkout": command}}
             bootstrap_recipe = env.get_template(template_path).render(**context)
 
-        Bootstrap = collections.namedtuple("Bootstrap", ["image", "recipe"])
+        Bootstrap = namedtuple("Bootstrap", ["image", "recipe"])
         return Bootstrap(image=self.bootstrap_image, recipe=bootstrap_recipe)
 
     @tengine.context_property
@@ -303,7 +304,7 @@ def render_phase(self):
         render_bootstrap = bool(self.bootstrap_image)
         render_build = not (self.last_phase == "bootstrap")
         render_final = self.last_phase in (None, "final")
-        Render = collections.namedtuple("Render", ["bootstrap", "build", "final"])
+        Render = namedtuple("Render", ["bootstrap", "build", "final"])
         return Render(bootstrap=render_bootstrap, build=render_build, final=render_final)
 
     def __call__(self):

lib/spack/spack/cray_manifest.py

@@ -90,7 +90,7 @@ def spec_from_entry(entry):
         name=entry["name"], version=entry["version"], compiler=compiler_str, arch=arch_str
     )
 
-    pkg_cls = spack.repo.path.get_pkg_class(entry["name"])
+    pkg_cls = spack.repo.PATH.get_pkg_class(entry["name"])
 
     if "parameters" in entry:
         variant_strs = list()

lib/spack/spack/database.py

@@ -21,10 +21,11 @@
 import contextlib
 import datetime
 import os
+import pathlib
 import socket
 import sys
 import time
-from typing import Dict, List, NamedTuple, Set, Type, Union
+from typing import Any, Callable, Dict, Generator, List, NamedTuple, Set, Type, Union
 
 try:
     import uuid
@@ -141,22 +142,23 @@ class InstallStatuses:
     def canonicalize(cls, query_arg):
         if query_arg is True:
             return [cls.INSTALLED]
-        elif query_arg is False:
+        if query_arg is False:
             return [cls.MISSING]
-        elif query_arg is any:
+        if query_arg is any:
             return [cls.INSTALLED, cls.DEPRECATED, cls.MISSING]
-        elif isinstance(query_arg, InstallStatus):
+        if isinstance(query_arg, InstallStatus):
             return [query_arg]
-        else:
-            try:  # Try block catches if it is not an iterable at all
-                if any(type(x) != InstallStatus for x in query_arg):
-                    raise TypeError
-            except TypeError:
-                raise TypeError(
-                    "installation query must be `any`, boolean, "
-                    "InstallStatus, or iterable of InstallStatus"
-                )
-            return query_arg
+        try:
+            statuses = list(query_arg)
+            if all(isinstance(x, InstallStatus) for x in statuses):
+                return statuses
+        except TypeError:
+            pass
+
+        raise TypeError(
+            "installation query must be `any`, boolean, "
+            "InstallStatus, or iterable of InstallStatus"
+        )
 
 
 class InstallRecord:
@@ -306,15 +308,16 @@ def __reduce__(self):
 
         """
 
-#: Data class to configure locks in Database objects
-#:
-#: Args:
-#:    enable (bool): whether to enable locks or not.
-#:    database_timeout (int or None): timeout for the database lock
-#:    package_timeout (int or None): timeout for the package lock
-
 
 class LockConfiguration(NamedTuple):
+    """Data class to configure locks in Database objects
+
+    Args:
+        enable: whether to enable locks or not.
+        database_timeout: timeout for the database lock
+        package_timeout: timeout for the package lock
+    """
+
     enable: bool
     database_timeout: Optional[int]
     package_timeout: Optional[int]
@@ -348,13 +351,230 @@ def lock_configuration(configuration):
     )
 
 
+def prefix_lock_path(root_dir: Union[str, pathlib.Path]) -> pathlib.Path:
+    """Returns the path of the prefix lock file, given the root directory.
+
+    Args:
+        root_dir: root directory containing the database directory
+    """
+    return pathlib.Path(root_dir) / _DB_DIRNAME / "prefix_lock"
+
+
+def failures_lock_path(root_dir: Union[str, pathlib.Path]) -> pathlib.Path:
+    """Returns the path of the failures lock file, given the root directory.
+
+    Args:
+        root_dir: root directory containing the database directory
+    """
+    return pathlib.Path(root_dir) / _DB_DIRNAME / "prefix_failures"
+
+
+class SpecLocker:
+    """Manages acquiring and releasing read or write locks on concrete specs."""
+
+    def __init__(self, lock_path: Union[str, pathlib.Path], default_timeout: Optional[float]):
+        self.lock_path = pathlib.Path(lock_path)
+        self.default_timeout = default_timeout
+
+        # Maps (spec.dag_hash(), spec.name) to the corresponding lock object
+        self.locks: Dict[Tuple[str, str], lk.Lock] = {}
+
+    def lock(self, spec: "spack.spec.Spec", timeout: Optional[float] = None) -> lk.Lock:
+        """Returns a lock on a concrete spec.
+
+        The lock is a byte range lock on the nth byte of a file.
+
+        The lock file is ``self.lock_path``.
+
+        n is the sys.maxsize-bit prefix of the DAG hash.  This makes likelihood of collision is
+        very low AND it gives us readers-writer lock semantics with just a single lockfile, so
+        no cleanup required.
+        """
+        assert spec.concrete, "cannot lock a non-concrete spec"
+        timeout = timeout or self.default_timeout
+        key = self._lock_key(spec)
+
+        if key not in self.locks:
+            self.locks[key] = self.raw_lock(spec, timeout=timeout)
+        else:
+            self.locks[key].default_timeout = timeout
+
+        return self.locks[key]
+
+    def raw_lock(self, spec: "spack.spec.Spec", timeout: Optional[float] = None) -> lk.Lock:
+        """Returns a raw lock for a Spec, but doesn't keep track of it."""
+        return lk.Lock(
+            str(self.lock_path),
+            start=spec.dag_hash_bit_prefix(bit_length(sys.maxsize)),
+            length=1,
+            default_timeout=timeout,
+            desc=spec.name,
+        )
+
+    def has_lock(self, spec: "spack.spec.Spec") -> bool:
+        """Returns True if the spec is already managed by this spec locker"""
+        return self._lock_key(spec) in self.locks
+
+    def _lock_key(self, spec: "spack.spec.Spec") -> Tuple[str, str]:
+        return (spec.dag_hash(), spec.name)
+
+    @contextlib.contextmanager
+    def write_lock(self, spec: "spack.spec.Spec") -> Generator["SpecLocker", None, None]:
+        lock = self.lock(spec)
+        lock.acquire_write()
+
+        try:
+            yield self
+        except lk.LockError:
+            # This addresses the case where a nested lock attempt fails inside
+            # of this context manager
+            raise
+        except (Exception, KeyboardInterrupt):
+            lock.release_write()
+            raise
+        else:
+            lock.release_write()
+
+    def clear(self, spec: "spack.spec.Spec") -> Tuple[bool, Optional[lk.Lock]]:
+        key = self._lock_key(spec)
+        lock = self.locks.pop(key, None)
+        return bool(lock), lock
+
+    def clear_all(self, clear_fn: Optional[Callable[[lk.Lock], Any]] = None) -> None:
+        if clear_fn is not None:
+            for lock in self.locks.values():
+                clear_fn(lock)
+        self.locks.clear()
+
+
+class FailureTracker:
+    """Tracks installation failures.
+
+    Prefix failure marking takes the form of a byte range lock on the nth
+    byte of a file for coordinating between concurrent parallel build
+    processes and a persistent file, named with the full hash and
+    containing the spec, in a subdirectory of the database to enable
+    persistence across overlapping but separate related build processes.
+
+    The failure lock file lives alongside the install DB.
+
+    ``n`` is the sys.maxsize-bit prefix of the associated DAG hash to make
+    the likelihood of collision very low with no cleanup required.
+    """
+
+    def __init__(self, root_dir: Union[str, pathlib.Path], default_timeout: Optional[float]):
+        #: Ensure a persistent location for dealing with parallel installation
+        #: failures (e.g., across near-concurrent processes).
+        self.dir = pathlib.Path(root_dir) / _DB_DIRNAME / "failures"
+        self.dir.mkdir(parents=True, exist_ok=True)
+
+        self.locker = SpecLocker(failures_lock_path(root_dir), default_timeout=default_timeout)
+
+    def clear(self, spec: "spack.spec.Spec", force: bool = False) -> None:
+        """Removes any persistent and cached failure tracking for the spec.
+
+        see `mark()`.
+
+        Args:
+            spec: the spec whose failure indicators are being removed
+            force: True if the failure information should be cleared when a failure lock
+                exists for the file, or False if the failure should not be cleared (e.g.,
+                it may be associated with a concurrent build)
+        """
+        locked = self.lock_taken(spec)
+        if locked and not force:
+            tty.msg(f"Retaining failure marking for {spec.name} due to lock")
+            return
+
+        if locked:
+            tty.warn(f"Removing failure marking despite lock for {spec.name}")
+
+        succeeded, lock = self.locker.clear(spec)
+        if succeeded and lock is not None:
+            lock.release_write()
+
+        if self.persistent_mark(spec):
+            path = self._path(spec)
+            tty.debug(f"Removing failure marking for {spec.name}")
+            try:
+                path.unlink()
+            except OSError as err:
+                tty.warn(
+                    f"Unable to remove failure marking for {spec.name} ({str(path)}): {str(err)}"
+                )
+
+    def clear_all(self) -> None:
+        """Force remove install failure tracking files."""
+        tty.debug("Releasing prefix failure locks")
+        self.locker.clear_all(
+            clear_fn=lambda x: x.release_write() if x.is_write_locked() else True
+        )
+
+        tty.debug("Removing prefix failure tracking files")
+        try:
+            for fail_mark in os.listdir(str(self.dir)):
+                try:
+                    (self.dir / fail_mark).unlink()
+                except OSError as exc:
+                    tty.warn(f"Unable to remove failure marking file {fail_mark}: {str(exc)}")
+        except OSError as exc:
+            tty.warn(f"Unable to remove failure marking files: {str(exc)}")
+
+    def mark(self, spec: "spack.spec.Spec") -> lk.Lock:
+        """Marks a spec as failing to install.
+
+        Args:
+            spec: spec that failed to install
+        """
+        # Dump the spec to the failure file for (manual) debugging purposes
+        path = self._path(spec)
+        path.write_text(spec.to_json())
+
+        # Also ensure a failure lock is taken to prevent cleanup removal
+        # of failure status information during a concurrent parallel build.
+        if not self.locker.has_lock(spec):
+            try:
+                mark = self.locker.lock(spec)
+                mark.acquire_write()
+            except lk.LockTimeoutError:
+                # Unlikely that another process failed to install at the same
+                # time but log it anyway.
+                tty.debug(f"PID {os.getpid()} failed to mark install failure for {spec.name}")
+                tty.warn(f"Unable to mark {spec.name} as failed.")
+
+        return self.locker.lock(spec)
+
+    def has_failed(self, spec: "spack.spec.Spec") -> bool:
+        """Return True if the spec is marked as failed."""
+        # The failure was detected in this process.
+        if self.locker.has_lock(spec):
+            return True
+
+        # The failure was detected by a concurrent process (e.g., an srun),
+        # which is expected to be holding a write lock if that is the case.
+        if self.lock_taken(spec):
+            return True
+
+        # Determine if the spec may have been marked as failed by a separate
+        # spack build process running concurrently.
+        return self.persistent_mark(spec)
+
+    def lock_taken(self, spec: "spack.spec.Spec") -> bool:
+        """Return True if another process has a failure lock on the spec."""
+        check = self.locker.raw_lock(spec)
+        return check.is_write_locked()
+
+    def persistent_mark(self, spec: "spack.spec.Spec") -> bool:
+        """Determine if the spec has a persistent failure marking."""
+        return self._path(spec).exists()
+
+    def _path(self, spec: "spack.spec.Spec") -> pathlib.Path:
+        """Return the path to the spec's failure file, which may not exist."""
+        assert spec.concrete, "concrete spec required for failure path"
+        return self.dir / f"{spec.name}-{spec.dag_hash()}"
+
+
 class Database:
-    #: Per-process lock objects for each install prefix
-    _prefix_locks: Dict[str, lk.Lock] = {}
-
-    #: Per-process failure (lock) objects for each install prefix
-    _prefix_failures: Dict[str, lk.Lock] = {}
-
     #: Fields written for each install record
     record_fields: Tuple[str, ...] = DEFAULT_INSTALL_RECORD_FIELDS
 
@@ -392,24 +612,10 @@ def __init__(
         self._verifier_path = os.path.join(self.database_directory, "index_verifier")
         self._lock_path = os.path.join(self.database_directory, "lock")
 
-        # This is for other classes to use to lock prefix directories.
-        self.prefix_lock_path = os.path.join(self.database_directory, "prefix_lock")
-
-        # Ensure a persistent location for dealing with parallel installation
-        # failures (e.g., across near-concurrent processes).
-        self._failure_dir = os.path.join(self.database_directory, "failures")
-
-        # Support special locks for handling parallel installation failures
-        # of a spec.
-        self.prefix_fail_path = os.path.join(self.database_directory, "prefix_failures")
-
         # Create needed directories and files
         if not is_upstream and not os.path.exists(self.database_directory):
             fs.mkdirp(self.database_directory)
 
-        if not is_upstream and not os.path.exists(self._failure_dir):
-            fs.mkdirp(self._failure_dir)
-
         self.is_upstream = is_upstream
         self.last_seen_verifier = ""
         # Failed write transactions (interrupted by exceptions) will alert
@@ -423,15 +629,7 @@ def __init__(
 
         # initialize rest of state.
         self.db_lock_timeout = lock_cfg.database_timeout
-        self.package_lock_timeout = lock_cfg.package_timeout
-
         tty.debug("DATABASE LOCK TIMEOUT: {0}s".format(str(self.db_lock_timeout)))
-        timeout_format_str = (
-            "{0}s".format(str(self.package_lock_timeout))
-            if self.package_lock_timeout
-            else "No timeout"
-        )
-        tty.debug("PACKAGE LOCK TIMEOUT: {0}".format(str(timeout_format_str)))
 
         self.lock: Union[ForbiddenLock, lk.Lock]
         if self.is_upstream:
@@ -471,212 +669,6 @@ def read_transaction(self):
         """Get a read lock context manager for use in a `with` block."""
         return self._read_transaction_impl(self.lock, acquire=self._read)
 
-    def _failed_spec_path(self, spec):
-        """Return the path to the spec's failure file, which may not exist."""
-        if not spec.concrete:
-            raise ValueError("Concrete spec required for failure path for {0}".format(spec.name))
-
-        return os.path.join(self._failure_dir, "{0}-{1}".format(spec.name, spec.dag_hash()))
-
-    def clear_all_failures(self) -> None:
-        """Force remove install failure tracking files."""
-        tty.debug("Releasing prefix failure locks")
-        for pkg_id in list(self._prefix_failures.keys()):
-            lock = self._prefix_failures.pop(pkg_id, None)
-            if lock:
-                lock.release_write()
-
-        # Remove all failure markings (aka files)
-        tty.debug("Removing prefix failure tracking files")
-        for fail_mark in os.listdir(self._failure_dir):
-            try:
-                os.remove(os.path.join(self._failure_dir, fail_mark))
-            except OSError as exc:
-                tty.warn(
-                    "Unable to remove failure marking file {0}: {1}".format(fail_mark, str(exc))
-                )
-
-    def clear_failure(self, spec: "spack.spec.Spec", force: bool = False) -> None:
-        """
-        Remove any persistent and cached failure tracking for the spec.
-
-        see `mark_failed()`.
-
-        Args:
-            spec: the spec whose failure indicators are being removed
-            force: True if the failure information should be cleared when a prefix failure
-                lock exists for the file, or False if the failure should not be cleared (e.g.,
-                it may be associated with a concurrent build)
-        """
-        failure_locked = self.prefix_failure_locked(spec)
-        if failure_locked and not force:
-            tty.msg("Retaining failure marking for {0} due to lock".format(spec.name))
-            return
-
-        if failure_locked:
-            tty.warn("Removing failure marking despite lock for {0}".format(spec.name))
-
-        lock = self._prefix_failures.pop(spec.prefix, None)
-        if lock:
-            lock.release_write()
-
-        if self.prefix_failure_marked(spec):
-            try:
-                path = self._failed_spec_path(spec)
-                tty.debug("Removing failure marking for {0}".format(spec.name))
-                os.remove(path)
-            except OSError as err:
-                tty.warn(
-                    "Unable to remove failure marking for {0} ({1}): {2}".format(
-                        spec.name, path, str(err)
-                    )
-                )
-
-    def mark_failed(self, spec: "spack.spec.Spec") -> lk.Lock:
-        """
-        Mark a spec as failing to install.
-
-        Prefix failure marking takes the form of a byte range lock on the nth
-        byte of a file for coordinating between concurrent parallel build
-        processes and a persistent file, named with the full hash and
-        containing the spec, in a subdirectory of the database to enable
-        persistence across overlapping but separate related build processes.
-
-        The failure lock file, ``spack.store.STORE.db.prefix_failures``, lives
-        alongside the install DB. ``n`` is the sys.maxsize-bit prefix of the
-        associated DAG hash to make the likelihood of collision very low with
-        no cleanup required.
-        """
-        # Dump the spec to the failure file for (manual) debugging purposes
-        path = self._failed_spec_path(spec)
-        with open(path, "w") as f:
-            spec.to_json(f)
-
-        # Also ensure a failure lock is taken to prevent cleanup removal
-        # of failure status information during a concurrent parallel build.
-        err = "Unable to mark {0.name} as failed."
-
-        prefix = spec.prefix
-        if prefix not in self._prefix_failures:
-            mark = lk.Lock(
-                self.prefix_fail_path,
-                start=spec.dag_hash_bit_prefix(bit_length(sys.maxsize)),
-                length=1,
-                default_timeout=self.package_lock_timeout,
-                desc=spec.name,
-            )
-
-            try:
-                mark.acquire_write()
-            except lk.LockTimeoutError:
-                # Unlikely that another process failed to install at the same
-                # time but log it anyway.
-                tty.debug(
-                    "PID {0} failed to mark install failure for {1}".format(os.getpid(), spec.name)
-                )
-                tty.warn(err.format(spec))
-
-            # Whether we or another process marked it as a failure, track it
-            # as such locally.
-            self._prefix_failures[prefix] = mark
-
-        return self._prefix_failures[prefix]
-
-    def prefix_failed(self, spec: "spack.spec.Spec") -> bool:
-        """Return True if the prefix (installation) is marked as failed."""
-        # The failure was detected in this process.
-        if spec.prefix in self._prefix_failures:
-            return True
-
-        # The failure was detected by a concurrent process (e.g., an srun),
-        # which is expected to be holding a write lock if that is the case.
-        if self.prefix_failure_locked(spec):
-            return True
-
-        # Determine if the spec may have been marked as failed by a separate
-        # spack build process running concurrently.
-        return self.prefix_failure_marked(spec)
-
-    def prefix_failure_locked(self, spec: "spack.spec.Spec") -> bool:
-        """Return True if a process has a failure lock on the spec."""
-        check = lk.Lock(
-            self.prefix_fail_path,
-            start=spec.dag_hash_bit_prefix(bit_length(sys.maxsize)),
-            length=1,
-            default_timeout=self.package_lock_timeout,
-            desc=spec.name,
-        )
-
-        return check.is_write_locked()
-
-    def prefix_failure_marked(self, spec: "spack.spec.Spec") -> bool:
-        """Determine if the spec has a persistent failure marking."""
-        return os.path.exists(self._failed_spec_path(spec))
-
-    def prefix_lock(self, spec: "spack.spec.Spec", timeout: Optional[float] = None) -> lk.Lock:
-        """Get a lock on a particular spec's installation directory.
-
-        NOTE: The installation directory **does not** need to exist.
-
-        Prefix lock is a byte range lock on the nth byte of a file.
-
-        The lock file is ``spack.store.STORE.db.prefix_lock`` -- the DB
-        tells us what to call it and it lives alongside the install DB.
-
-        n is the sys.maxsize-bit prefix of the DAG hash.  This makes
-        likelihood of collision is very low AND it gives us
-        readers-writer lock semantics with just a single lockfile, so no
-        cleanup required.
-        """
-        timeout = timeout or self.package_lock_timeout
-        prefix = spec.prefix
-        if prefix not in self._prefix_locks:
-            self._prefix_locks[prefix] = lk.Lock(
-                self.prefix_lock_path,
-                start=spec.dag_hash_bit_prefix(bit_length(sys.maxsize)),
-                length=1,
-                default_timeout=timeout,
-                desc=spec.name,
-            )
-        elif timeout != self._prefix_locks[prefix].default_timeout:
-            self._prefix_locks[prefix].default_timeout = timeout
-
-        return self._prefix_locks[prefix]
-
-    @contextlib.contextmanager
-    def prefix_read_lock(self, spec):
-        prefix_lock = self.prefix_lock(spec)
-        prefix_lock.acquire_read()
-
-        try:
-            yield self
-        except lk.LockError:
-            # This addresses the case where a nested lock attempt fails inside
-            # of this context manager
-            raise
-        except (Exception, KeyboardInterrupt):
-            prefix_lock.release_read()
-            raise
-        else:
-            prefix_lock.release_read()
-
-    @contextlib.contextmanager
-    def prefix_write_lock(self, spec):
-        prefix_lock = self.prefix_lock(spec)
-        prefix_lock.acquire_write()
-
-        try:
-            yield self
-        except lk.LockError:
-            # This addresses the case where a nested lock attempt fails inside
-            # of this context manager
-            raise
-        except (Exception, KeyboardInterrupt):
-            prefix_lock.release_write()
-            raise
-        else:
-            prefix_lock.release_write()
-
     def _write_to_file(self, stream):
         """Write out the database in JSON format to the stream passed
         as argument.

lib/spack/spack/directives.py

@@ -33,7 +33,7 @@ class OpenMpi(Package):
 import functools
 import os.path
 import re
-from typing import List, Optional, Set, Union
+from typing import Any, Callable, List, Optional, Set, Tuple, Union
 
 import llnl.util.lang
 import llnl.util.tty.color
@@ -520,7 +520,8 @@ def _execute_conflicts(pkg):
 
         # Save in a list the conflicts and the associated custom messages
         when_spec_list = pkg.conflicts.setdefault(conflict_spec, [])
-        when_spec_list.append((when_spec, msg))
+        msg_with_name = f"{pkg.name}: {msg}" if msg is not None else msg
+        when_spec_list.append((when_spec, msg_with_name))
 
     return _execute_conflicts
 
@@ -663,39 +664,35 @@ def _execute_patch(pkg_or_dep):
 
 @directive("variants")
 def variant(
-    name,
-    default=None,
-    description="",
-    values=None,
-    multi=None,
-    validator=None,
-    when=None,
-    sticky=False,
+    name: str,
+    default: Optional[Any] = None,
+    description: str = "",
+    values: Optional[Union[collections.abc.Sequence, Callable[[Any], bool]]] = None,
+    multi: Optional[bool] = None,
+    validator: Optional[Callable[[str, str, Tuple[Any, ...]], None]] = None,
+    when: Optional[Union[str, bool]] = None,
+    sticky: bool = False,
 ):
-    """Define a variant for the package. Packager can specify a default
-    value as well as a text description.
+    """Define a variant for the package.
+
+    Packager can specify a default value as well as a text description.
 
     Args:
-        name (str): name of the variant
-        default (str or bool): default value for the variant, if not
-            specified otherwise the default will be False for a boolean
-            variant and 'nothing' for a multi-valued variant
-        description (str): description of the purpose of the variant
-        values (tuple or typing.Callable): either a tuple of strings containing the
-            allowed values, or a callable accepting one value and returning
-            True if it is valid
-        multi (bool): if False only one value per spec is allowed for
-            this variant
-        validator (typing.Callable): optional group validator to enforce additional
-            logic. It receives the package name, the variant name and a tuple
-            of values and should raise an instance of SpackError if the group
-            doesn't meet the additional constraints
-        when (spack.spec.Spec, bool): optional condition on which the
-            variant applies
-        sticky (bool): the variant should not be changed by the concretizer to
-            find a valid concrete spec.
+        name: Name of the variant
+        default: Default value for the variant, if not specified otherwise the default will be
+            False for a boolean variant and 'nothing' for a multi-valued variant
+        description: Description of the purpose of the variant
+        values: Either a tuple of strings containing the allowed values, or a callable accepting
+            one value and returning True if it is valid
+        multi: If False only one value per spec is allowed for this variant
+        validator: Optional group validator to enforce additional logic. It receives the package
+            name, the variant name and a tuple of values and should raise an instance of SpackError
+            if the group doesn't meet the additional constraints
+        when: Optional condition on which the variant applies
+        sticky: The variant should not be changed by the concretizer to find a valid concrete spec
+
     Raises:
-        DirectiveError: if arguments passed to the directive are invalid
+        DirectiveError: If arguments passed to the directive are invalid
     """
 
     def format_error(msg, pkg):
@@ -900,7 +897,8 @@ def _execute_requires(pkg):
 
         # Save in a list the requirements and the associated custom messages
         when_spec_list = pkg.requirements.setdefault(tuple(requirement_specs), [])
-        when_spec_list.append((when_spec, policy, msg))
+        msg_with_name = f"{pkg.name}: {msg}" if msg is not None else msg
+        when_spec_list.append((when_spec, policy, msg_with_name))
 
     return _execute_requires
 

lib/spack/spack/directory_layout.py

@@ -11,6 +11,7 @@
 import shutil
 import sys
 from contextlib import contextmanager
+from pathlib import Path
 
 import llnl.util.filesystem as fs
 import llnl.util.tty as tty
@@ -104,7 +105,7 @@ def relative_path_for_spec(self, spec):
 
         projection = spack.projections.get_projection(self.projections, spec)
         path = spec.format(projection)
-        return path
+        return str(Path(path))
 
     def write_spec(self, spec, path):
         """Write a spec out to a file."""

lib/spack/spack/environment/environment.py

@@ -203,7 +203,7 @@ def activate(env, use_env_repo=False):
         env.store_token = spack.store.reinitialize()
 
     if use_env_repo:
-        spack.repo.path.put_first(env.repo)
+        spack.repo.PATH.put_first(env.repo)
 
     tty.debug("Using environment '%s'" % env.name)
 
@@ -227,7 +227,7 @@ def deactivate():
 
     # use _repo so we only remove if a repo was actually constructed
     if _active_environment._repo:
-        spack.repo.path.remove(_active_environment._repo)
+        spack.repo.PATH.remove(_active_environment._repo)
 
     tty.debug("Deactivated environment '%s'" % _active_environment.name)
 
@@ -1084,8 +1084,8 @@ def add(self, user_spec, list_name=user_speclist_name):
         if list_name == user_speclist_name:
             if spec.anonymous:
                 raise SpackEnvironmentError("cannot add anonymous specs to an environment")
-            elif not spack.repo.path.exists(spec.name) and not spec.abstract_hash:
-                virtuals = spack.repo.path.provider_index.providers.keys()
+            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)
@@ -1262,7 +1262,7 @@ def develop(self, spec: Spec, path: str, clone: bool = False) -> bool:
             # better if we can create the `source_path` directly into its final
             # destination.
             abspath = spack.util.path.canonicalize_path(path, default_wd=self.path)
-            pkg_cls = spack.repo.path.get_pkg_class(spec.name)
+            pkg_cls = spack.repo.PATH.get_pkg_class(spec.name)
             # We construct a package class ourselves, rather than asking for
             # Spec.package, since Spec only allows this when it is concrete
             package = pkg_cls(spec)
@@ -1490,7 +1490,7 @@ def _concretize_separately(self, tests=False):
         # for a write lock. We do this indirectly by retrieving the
         # provider index, which should in turn trigger the update of
         # all the indexes if there's any need for that.
-        _ = spack.repo.path.provider_index
+        _ = spack.repo.PATH.provider_index
 
         # Ensure we have compilers in compilers.yaml to avoid that
         # processes try to write the config file in parallel
@@ -2280,7 +2280,7 @@ def _add_to_environment_repository(self, spec_node: Spec) -> None:
         repository = spack.repo.create_or_construct(repository_dir, spec_node.namespace)
         pkg_dir = repository.dirname_for_package_name(spec_node.name)
         fs.mkdirp(pkg_dir)
-        spack.repo.path.dump_provenance(spec_node, pkg_dir)
+        spack.repo.PATH.dump_provenance(spec_node, pkg_dir)
 
     def manifest_uptodate_or_warn(self):
         """Emits a warning if the manifest file is not up-to-date."""
@@ -2448,13 +2448,13 @@ def make_repo_path(root):
 def prepare_config_scope(env):
     """Add env's scope to the global configuration search path."""
     for scope in env.config_scopes():
-        spack.config.config.push_scope(scope)
+        spack.config.CONFIG.push_scope(scope)
 
 
 def deactivate_config_scope(env):
     """Remove any scopes from env from the global config path."""
     for scope in env.config_scopes():
-        spack.config.config.remove_scope(scope.name)
+        spack.config.CONFIG.remove_scope(scope.name)
 
 
 def manifest_file(env_name_or_dir):

lib/spack/spack/graph.py

@@ -535,7 +535,7 @@ def edge_entry(self, edge):
 
 def _static_edges(specs, deptype):
     for spec in specs:
-        pkg_cls = spack.repo.path.get_pkg_class(spec.name)
+        pkg_cls = spack.repo.PATH.get_pkg_class(spec.name)
         possible = pkg_cls.possible_dependencies(expand_virtuals=True, deptype=deptype)
 
         for parent_name, dependencies in possible.items():

lib/spack/spack/hash_types.py

@@ -49,7 +49,7 @@ def __call__(self, spec):
 
 
 def _content_hash_override(spec):
-    pkg_cls = spack.repo.path.get_pkg_class(spec.name)
+    pkg_cls = spack.repo.PATH.get_pkg_class(spec.name)
     pkg = pkg_cls(spec)
     return pkg.content_hash()
 

lib/spack/spack/install_test.py

@@ -1147,12 +1147,12 @@ def write_test_result(self, spec, result):
     def write_reproducibility_data(self):
         for spec in self.specs:
             repo_cache_path = self.stage.repo.join(spec.name)
-            spack.repo.path.dump_provenance(spec, repo_cache_path)
+            spack.repo.PATH.dump_provenance(spec, repo_cache_path)
             for vspec in spec.package.virtuals_provided:
                 repo_cache_path = self.stage.repo.join(vspec.name)
                 if not os.path.exists(repo_cache_path):
                     try:
-                        spack.repo.path.dump_provenance(vspec, repo_cache_path)
+                        spack.repo.PATH.dump_provenance(vspec, repo_cache_path)
                     except spack.repo.UnknownPackageError:
                         pass  # not all virtuals have package files
 

lib/spack/spack/installer.py

@@ -519,13 +519,6 @@ def _try_install_from_binary_cache(
     )
 
 
-def clear_failures() -> None:
-    """
-    Remove all failure tracking markers for the Spack instance.
-    """
-    spack.store.STORE.db.clear_all_failures()
-
-
 def combine_phase_logs(phase_log_files: List[str], log_path: str) -> None:
     """
     Read set or list of logs and combine them into one file.
@@ -597,7 +590,7 @@ def dump_packages(spec: "spack.spec.Spec", path: str) -> None:
         # Get the location of the package in the dest repo.
         dest_pkg_dir = repo.dirname_for_package_name(node.name)
         if node is spec:
-            spack.repo.path.dump_provenance(node, dest_pkg_dir)
+            spack.repo.PATH.dump_provenance(node, dest_pkg_dir)
         elif source_pkg_dir:
             fs.install_tree(source_pkg_dir, dest_pkg_dir)
 
@@ -1126,15 +1119,13 @@ class PackageInstaller:
     instance.
     """
 
-    def __init__(self, installs: List[Tuple["spack.package_base.PackageBase", dict]] = []):
+    def __init__(self, installs: List[Tuple["spack.package_base.PackageBase", dict]] = []) -> None:
         """Initialize the installer.
 
         Args:
             installs (list): list of tuples, where each
                 tuple consists of a package (PackageBase) and its associated
                  install arguments (dict)
-        Return:
-            PackageInstaller: instance
         """
         # List of build requests
         self.build_requests = [BuildRequest(pkg, install_args) for pkg, install_args in installs]
@@ -1287,7 +1278,7 @@ def _check_deps_status(self, request: BuildRequest) -> None:
             dep_id = package_id(dep_pkg)
 
             # Check for failure since a prefix lock is not required
-            if spack.store.STORE.db.prefix_failed(dep):
+            if spack.store.STORE.failure_tracker.has_failed(dep):
                 action = "'spack install' the dependency"
                 msg = "{0} is marked as an install failure: {1}".format(dep_id, action)
                 raise InstallError(err.format(request.pkg_id, msg), pkg=dep_pkg)
@@ -1502,7 +1493,7 @@ def _ensure_locked(
             if lock is None:
                 tty.debug(msg.format("Acquiring", desc, pkg_id, pretty_seconds(timeout or 0)))
                 op = "acquire"
-                lock = spack.store.STORE.db.prefix_lock(pkg.spec, timeout)
+                lock = spack.store.STORE.prefix_locker.lock(pkg.spec, timeout)
                 if timeout != lock.default_timeout:
                     tty.warn(
                         "Expected prefix lock timeout {0}, not {1}".format(
@@ -1627,12 +1618,12 @@ def _add_tasks(self, request: BuildRequest, all_deps):
                 # Clear any persistent failure markings _unless_ they are
                 # associated with another process in this parallel build
                 # of the spec.
-                spack.store.STORE.db.clear_failure(dep, force=False)
+                spack.store.STORE.failure_tracker.clear(dep, force=False)
 
         install_package = request.install_args.get("install_package")
         if install_package and request.pkg_id not in self.build_tasks:
             # Be sure to clear any previous failure
-            spack.store.STORE.db.clear_failure(request.spec, force=True)
+            spack.store.STORE.failure_tracker.clear(request.spec, force=True)
 
             # If not installing dependencies, then determine their
             # installation status before proceeding
@@ -1888,7 +1879,7 @@ def _update_failed(
         err = "" if exc is None else ": {0}".format(str(exc))
         tty.debug("Flagging {0} as failed{1}".format(pkg_id, err))
         if mark:
-            self.failed[pkg_id] = spack.store.STORE.db.mark_failed(task.pkg.spec)
+            self.failed[pkg_id] = spack.store.STORE.failure_tracker.mark(task.pkg.spec)
         else:
             self.failed[pkg_id] = None
         task.status = STATUS_FAILED
@@ -2074,7 +2065,7 @@ def install(self) -> None:
 
             # Flag a failed spec.  Do not need an (install) prefix lock since
             # assume using a separate (failed) prefix lock file.
-            if pkg_id in self.failed or spack.store.STORE.db.prefix_failed(spec):
+            if pkg_id in self.failed or spack.store.STORE.failure_tracker.has_failed(spec):
                 term_status.clear()
                 tty.warn("{0} failed to install".format(pkg_id))
                 self._update_failed(task)

lib/spack/spack/main.py

@@ -602,10 +602,10 @@ def setup_main_options(args):
 
         key = syaml.syaml_str("repos")
         key.override = True
-        spack.config.config.scopes["command_line"].sections["repos"] = syaml.syaml_dict(
+        spack.config.CONFIG.scopes["command_line"].sections["repos"] = syaml.syaml_dict(
             [(key, [spack.paths.mock_packages_path])]
         )
-        spack.repo.path = spack.repo.create(spack.config.config)
+        spack.repo.PATH = spack.repo.create(spack.config.CONFIG)
 
     # If the user asked for it, don't check ssl certs.
     if args.insecure:
@@ -930,7 +930,7 @@ def _main(argv=None):
 
     # make spack.config aware of any command line configuration scopes
     if args.config_scopes:
-        spack.config.command_line_scopes = args.config_scopes
+        spack.config.COMMAND_LINE_SCOPES = args.config_scopes
 
     # ensure options on spack command come before everything
     setup_main_options(args)

lib/spack/spack/mirror.py

@@ -442,7 +442,7 @@ def mirror_archive_paths(fetcher, per_package_ref, spec=None):
     storage path of the resource associated with the specified ``fetcher``."""
     ext = None
     if spec:
-        pkg_cls = spack.repo.path.get_pkg_class(spec.name)
+        pkg_cls = spack.repo.PATH.get_pkg_class(spec.name)
         versions = pkg_cls.versions.get(spec.version, {})
         ext = versions.get("extension", None)
     # If the spec does not explicitly specify an extension (the default case),
@@ -474,7 +474,7 @@ def get_all_versions(specs):
     """
     version_specs = []
     for spec in specs:
-        pkg_cls = spack.repo.path.get_pkg_class(spec.name)
+        pkg_cls = spack.repo.PATH.get_pkg_class(spec.name)
         # Skip any package that has no known versions.
         if not pkg_cls.versions:
             tty.msg("No safe (checksummed) versions for package %s" % pkg_cls.name)

lib/spack/spack/modules/common.py

@@ -833,7 +833,7 @@ def ensure_modules_are_enabled_or_warn():
         return
 
     # Check if we have custom TCL module sections
-    for scope in spack.config.config.file_scopes:
+    for scope in spack.config.CONFIG.file_scopes:
         # Skip default configuration
         if scope.name.startswith("default"):
             continue

lib/spack/spack/modules/lmod.py

@@ -143,7 +143,7 @@ def hierarchy_tokens(self):
 
         # Check if all the tokens in the hierarchy are virtual specs.
         # If not warn the user and raise an error.
-        not_virtual = [t for t in tokens if t != "compiler" and not spack.repo.path.is_virtual(t)]
+        not_virtual = [t for t in tokens if t != "compiler" and not spack.repo.PATH.is_virtual(t)]
         if not_virtual:
             msg = "Non-virtual specs in 'hierarchy' list for lmod: {0}\n"
             msg += "Please check the 'modules.yaml' configuration files"

lib/spack/spack/multimethod.py

@@ -236,7 +236,7 @@ def install(self, prefix):
 
         # Create a multimethod with this name if there is not one already
         original_method = MultiMethodMeta._locals.get(method.__name__)
-        if not type(original_method) == SpecMultiMethod:
+        if not isinstance(original_method, SpecMultiMethod):
             original_method = SpecMultiMethod(original_method)
 
         if self.spec is not None:

lib/spack/spack/package_base.py

@@ -665,7 +665,7 @@ def __init__(self, spec):
         self.win_rpath = fsys.WindowsSimulatedRPath(self)
 
         if self.is_extension:
-            pkg_cls = spack.repo.path.get_pkg_class(self.extendee_spec.name)
+            pkg_cls = spack.repo.PATH.get_pkg_class(self.extendee_spec.name)
             pkg_cls(self.extendee_spec)._check_extendable()
 
         super().__init__()
@@ -728,11 +728,11 @@ def possible_dependencies(
                 continue
 
             # expand virtuals if enabled, otherwise just stop at virtuals
-            if spack.repo.path.is_virtual(name):
+            if spack.repo.PATH.is_virtual(name):
                 if virtuals is not None:
                     virtuals.add(name)
                 if expand_virtuals:
-                    providers = spack.repo.path.providers_for(name)
+                    providers = spack.repo.PATH.providers_for(name)
                     dep_names = [spec.name for spec in providers]
                 else:
                     visited.setdefault(cls.name, set()).add(name)
@@ -756,7 +756,7 @@ def possible_dependencies(
                     continue
 
                 try:
-                    dep_cls = spack.repo.path.get_pkg_class(dep_name)
+                    dep_cls = spack.repo.PATH.get_pkg_class(dep_name)
                 except spack.repo.UnknownPackageError:
                     # log unknown packages
                     missing.setdefault(cls.name, set()).add(dep_name)
@@ -2209,7 +2209,7 @@ def uninstall_by_spec(spec, force=False, deprecator=None):
             pkg = None
 
         # Pre-uninstall hook runs first.
-        with spack.store.STORE.db.prefix_write_lock(spec):
+        with spack.store.STORE.prefix_locker.write_lock(spec):
             if pkg is not None:
                 try:
                     spack.hooks.pre_uninstall(spec)
@@ -2459,8 +2459,8 @@ def possible_dependencies(*pkg_or_spec, **kwargs):
         if not isinstance(pos, spack.spec.Spec):
             pos = spack.spec.Spec(pos)
 
-        if spack.repo.path.is_virtual(pos.name):
-            packages.extend(p.package_class for p in spack.repo.path.providers_for(pos.name))
+        if spack.repo.PATH.is_virtual(pos.name):
+            packages.extend(p.package_class for p in spack.repo.PATH.providers_for(pos.name))
             continue
         else:
             packages.append(pos.package_class)

lib/spack/spack/package_prefs.py

@@ -147,7 +147,7 @@ def preferred_variants(cls, pkg_name):
             variants = " ".join(variants)
 
         # Only return variants that are actually supported by the package
-        pkg_cls = spack.repo.path.get_pkg_class(pkg_name)
+        pkg_cls = spack.repo.PATH.get_pkg_class(pkg_name)
         spec = spack.spec.Spec("%s %s" % (pkg_name, variants))
         return dict(
             (name, variant) for name, variant in spec.variants.items() if name in pkg_cls.variants
@@ -162,7 +162,7 @@ def spec_externals(spec):
     from spack.util.module_cmd import path_from_modules  # noqa: F401
 
     def _package(maybe_abstract_spec):
-        pkg_cls = spack.repo.path.get_pkg_class(spec.name)
+        pkg_cls = spack.repo.PATH.get_pkg_class(spec.name)
         return pkg_cls(maybe_abstract_spec)
 
     allpkgs = spack.config.get("packages")
@@ -199,7 +199,7 @@ def is_spec_buildable(spec):
     so_far = all_buildable  # the default "so far"
 
     def _package(s):
-        pkg_cls = spack.repo.path.get_pkg_class(s.name)
+        pkg_cls = spack.repo.PATH.get_pkg_class(s.name)
         return pkg_cls(s)
 
     # check whether any providers for this package override the default

lib/spack/spack/patch.py

@@ -238,7 +238,7 @@ def to_dict(self):
 
 def from_dict(dictionary, repository=None):
     """Create a patch from json dictionary."""
-    repository = repository or spack.repo.path
+    repository = repository or spack.repo.PATH
     owner = dictionary.get("owner")
     if "owner" not in dictionary:
         raise ValueError("Invalid patch dictionary: %s" % dictionary)

lib/spack/spack/paths.py

@@ -10,11 +10,12 @@
 dependencies.
 """
 import os
+from pathlib import PurePath
 
 import llnl.util.filesystem
 
 #: This file lives in $prefix/lib/spack/spack/__file__
-prefix = llnl.util.filesystem.ancestor(__file__, 4)
+prefix = str(PurePath(llnl.util.filesystem.ancestor(__file__, 4)))
 
 #: synonym for prefix
 spack_root = prefix
@@ -88,7 +89,7 @@ def _get_user_cache_path():
     return os.path.expanduser(os.getenv("SPACK_USER_CACHE_PATH") or "~%s.spack" % os.sep)
 
 
-user_cache_path = _get_user_cache_path()
+user_cache_path = str(PurePath(_get_user_cache_path()))
 
 #: junit, cdash, etc. reports about builds
 reports_path = os.path.join(user_cache_path, "reports")

lib/spack/spack/platforms/__init__.py

@@ -64,7 +64,7 @@ def use_platform(new_platform):
         host = _PickleableCallable(new_platform)
 
         # Clear configuration and compiler caches
-        spack.config.config.clear_caches()
+        spack.config.CONFIG.clear_caches()
         spack.compilers._cache_config_files = []
 
         yield new_platform
@@ -73,5 +73,5 @@ def use_platform(new_platform):
         host = original_host_fn
 
         # Clear configuration and compiler caches
-        spack.config.config.clear_caches()
+        spack.config.CONFIG.clear_caches()
         spack.compilers._cache_config_files = []

lib/spack/spack/repo.py

@@ -149,7 +149,7 @@ def compute_loader(self, fullname):
 
         # If it's a module in some repo, or if it is the repo's
         # namespace, let the repo handle it.
-        for repo in path.repos:
+        for repo in PATH.repos:
             # We are using the namespace of the repo and the repo contains the package
             if namespace == repo.full_namespace:
                 # With 2 nested conditionals we can call "repo.real_name" only once
@@ -163,7 +163,7 @@ def compute_loader(self, fullname):
 
         # No repo provides the namespace, but it is a valid prefix of
         # something in the RepoPath.
-        if path.by_namespace.is_prefix(fullname):
+        if PATH.by_namespace.is_prefix(fullname):
             return SpackNamespaceLoader()
 
         return None
@@ -184,9 +184,9 @@ def compute_loader(self, fullname):
 def packages_path():
     """Get the test repo if it is active, otherwise the builtin repo."""
     try:
-        return spack.repo.path.get_repo("builtin.mock").packages_path
+        return spack.repo.PATH.get_repo("builtin.mock").packages_path
     except spack.repo.UnknownNamespaceError:
-        return spack.repo.path.get_repo("builtin").packages_path
+        return spack.repo.PATH.get_repo("builtin").packages_path
 
 
 class GitExe:
@@ -282,7 +282,7 @@ def add_package_to_git_stage(packages):
     git = GitExe()
 
     for pkg_name in packages:
-        filename = spack.repo.path.filename_for_package_name(pkg_name)
+        filename = spack.repo.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)
 
@@ -647,7 +647,7 @@ class RepoPath:
     """
 
     def __init__(self, *repos, **kwargs):
-        cache = kwargs.get("cache", spack.caches.misc_cache)
+        cache = kwargs.get("cache", spack.caches.MISC_CACHE)
         self.repos = []
         self.by_namespace = nm.NamespaceTrie()
 
@@ -966,7 +966,7 @@ def check(condition, msg):
 
         # Indexes for this repository, computed lazily
         self._repo_index = None
-        self._cache = cache or spack.caches.misc_cache
+        self._cache = cache or spack.caches.MISC_CACHE
 
     def real_name(self, import_name):
         """Allow users to import Spack packages using Python identifiers.
@@ -1357,7 +1357,7 @@ def create_or_construct(path, namespace=None):
 
 def _path(configuration=None):
     """Get the singleton RepoPath instance for Spack."""
-    configuration = configuration or spack.config.config
+    configuration = configuration or spack.config.CONFIG
     return create(configuration=configuration)
 
 
@@ -1374,7 +1374,7 @@ def create(configuration):
 
 
 #: Singleton repo path instance
-path: Union[RepoPath, llnl.util.lang.Singleton] = llnl.util.lang.Singleton(_path)
+PATH: Union[RepoPath, llnl.util.lang.Singleton] = llnl.util.lang.Singleton(_path)
 
 # Add the finder to sys.meta_path
 REPOS_FINDER = ReposFinder()
@@ -1383,7 +1383,7 @@ def create(configuration):
 
 def all_package_names(include_virtuals=False):
     """Convenience wrapper around ``spack.repo.all_package_names()``."""
-    return path.all_package_names(include_virtuals)
+    return PATH.all_package_names(include_virtuals)
 
 
 @contextlib.contextmanager
@@ -1398,21 +1398,21 @@ def use_repositories(*paths_and_repos, **kwargs):
     Returns:
         Corresponding RepoPath object
     """
-    global path
+    global PATH
     # TODO (Python 2.7): remove this kwargs on deprecation of Python 2.7 support
     override = kwargs.get("override", True)
     paths = [getattr(x, "root", x) for x in paths_and_repos]
     scope_name = "use-repo-{}".format(uuid.uuid4())
     repos_key = "repos:" if override else "repos"
-    spack.config.config.push_scope(
+    spack.config.CONFIG.push_scope(
         spack.config.InternalConfigScope(name=scope_name, data={repos_key: paths})
     )
-    path, saved = create(configuration=spack.config.config), path
+    PATH, saved = create(configuration=spack.config.CONFIG), PATH
     try:
-        yield path
+        yield PATH
     finally:
-        spack.config.config.remove_scope(scope_name=scope_name)
-        path = saved
+        spack.config.CONFIG.remove_scope(scope_name=scope_name)
+        PATH = saved
 
 
 class MockRepositoryBuilder:

lib/spack/spack/schema/concretizer.py

@@ -28,6 +28,12 @@
             "unify": {
                 "oneOf": [{"type": "boolean"}, {"type": "string", "enum": ["when_possible"]}]
             },
+            "duplicates": {
+                "type": "object",
+                "properties": {
+                    "strategy": {"type": "string", "enum": ["none", "minimal", "full"]}
+                },
+            },
         },
     }
 }

lib/spack/spack/solver/asp.py

@@ -8,11 +8,12 @@
 import enum
 import itertools
 import os
+import pathlib
 import pprint
 import re
 import types
 import warnings
-from typing import List
+from typing import List, NamedTuple
 
 import archspec.cpu
 
@@ -50,6 +51,8 @@
 import spack.version as vn
 import spack.version.git_ref_lookup
 
+from .counter import FullDuplicatesCounter, MinimalDuplicatesCounter, NoDuplicatesCounter
+
 # these are from clingo.ast and bootstrapped later
 ASTType = None
 parse_files = None
@@ -77,9 +80,7 @@ def default_clingo_control():
     """Return a control object with the default settings used in Spack"""
     control = clingo.Control()
     control.configuration.configuration = "tweety"
-    control.configuration.solve.models = 0
     control.configuration.solver.heuristic = "Domain"
-    control.configuration.solve.parallel_mode = "1"
     control.configuration.solver.opt_strategy = "usc,one"
     return control
 
@@ -237,7 +238,7 @@ def listify(args):
 
 def packagize(pkg):
     if isinstance(pkg, str):
-        return spack.repo.path.get_pkg_class(pkg)
+        return spack.repo.PATH.get_pkg_class(pkg)
     else:
         return pkg
 
@@ -302,6 +303,8 @@ def argify(arg):
                 return clingo.String(str(arg))
             elif isinstance(arg, int):
                 return clingo.Number(arg)
+            elif isinstance(arg, AspFunction):
+                return clingo.Function(arg.name, [argify(x) for x in arg.args], positive=positive)
             else:
                 return clingo.String(str(arg))
 
@@ -322,6 +325,15 @@ def __getattr__(self, name):
 fn = AspFunctionBuilder()
 
 
+def _create_counter(specs, tests):
+    strategy = spack.config.CONFIG.get("concretizer:duplicates:strategy", "none")
+    if strategy == "full":
+        return FullDuplicatesCounter(specs, tests=tests)
+    if strategy == "minimal":
+        return MinimalDuplicatesCounter(specs, tests=tests)
+    return NoDuplicatesCounter(specs, tests=tests)
+
+
 def all_compilers_in_config():
     return spack.compilers.all_compilers()
 
@@ -342,7 +354,7 @@ def extend_flag_list(flag_list, new_flags):
 
 def check_packages_exist(specs):
     """Ensure all packages mentioned in specs exist."""
-    repo = spack.repo.path
+    repo = spack.repo.PATH
     for spec in specs:
         for s in spec.traverse():
             try:
@@ -513,15 +525,17 @@ def _compute_specs_from_answer_set(self):
         best = min(self.answers)
         opt, _, answer = best
         for input_spec in self.abstract_specs:
-            key = input_spec.name
+            node = SpecBuilder.make_node(pkg=input_spec.name)
             if input_spec.virtual:
-                providers = [spec.name for spec in answer.values() if spec.package.provides(key)]
-                key = providers[0]
-            candidate = answer.get(key)
+                providers = [
+                    spec.name for spec in answer.values() if spec.package.provides(input_spec.name)
+                ]
+                node = SpecBuilder.make_node(pkg=providers[0])
+            candidate = answer.get(node)
 
             if candidate and candidate.satisfies(input_spec):
-                self._concrete_specs.append(answer[key])
-                self._concrete_specs_by_input[input_spec] = answer[key]
+                self._concrete_specs.append(answer[node])
+                self._concrete_specs_by_input[input_spec] = answer[node]
             else:
                 self._unsolved_specs.append(input_spec)
 
@@ -529,7 +543,7 @@ def _compute_specs_from_answer_set(self):
 def _normalize_packages_yaml(packages_yaml):
     normalized_yaml = copy.copy(packages_yaml)
     for pkg_name in packages_yaml:
-        is_virtual = spack.repo.path.is_virtual(pkg_name)
+        is_virtual = spack.repo.PATH.is_virtual(pkg_name)
         if pkg_name == "all" or not is_virtual:
             continue
 
@@ -537,7 +551,7 @@ def _normalize_packages_yaml(packages_yaml):
         data = normalized_yaml.pop(pkg_name)
         is_buildable = data.get("buildable", True)
         if not is_buildable:
-            for provider in spack.repo.path.providers_for(pkg_name):
+            for provider in spack.repo.PATH.providers_for(pkg_name):
                 entry = normalized_yaml.setdefault(provider.name, {})
                 entry["buildable"] = False
 
@@ -572,16 +586,33 @@ def bootstrap_clingo():
         from clingo import parse_files
 
 
-def stringify(sym):
-    """Stringify symbols from clingo models.
+class NodeArgument(NamedTuple):
+    id: str
+    pkg: str
 
-    This will turn a ``clingo.Symbol`` into a string, or a sequence of ``clingo.Symbol``
-    objects into a tuple of strings.
 
+def intermediate_repr(sym):
+    """Returns an intermediate representation of clingo models for Spack's spec builder.
+
+    Currently, transforms symbols from clingo models either to strings or to NodeArgument objects.
+
+    Returns:
+        This will turn a ``clingo.Symbol`` into a string or NodeArgument, or a sequence of
+        ``clingo.Symbol`` objects into a tuple of those objects.
     """
     # TODO: simplify this when we no longer have to support older clingo versions.
     if isinstance(sym, (list, tuple)):
-        return tuple(stringify(a) for a in sym)
+        return tuple(intermediate_repr(a) for a in sym)
+
+    try:
+        if sym.name == "node":
+            return NodeArgument(
+                id=intermediate_repr(sym.arguments[0]), pkg=intermediate_repr(sym.arguments[1])
+            )
+    except RuntimeError:
+        # This happens when using clingo w/ CFFI and trying to access ".name" for symbols
+        # that are not functions
+        pass
 
     if clingo_cffi:
         # Clingo w/ CFFI will throw an exception on failure
@@ -596,10 +627,10 @@ def stringify(sym):
 def extract_args(model, predicate_name):
     """Extract the arguments to predicates with the provided name from a model.
 
-    Pull out all the predicates with name ``predicate_name`` from the model, and return
-    their stringified arguments as tuples.
+    Pull out all the predicates with name ``predicate_name`` from the model, and
+    return their intermediate representation.
     """
-    return [stringify(sym.arguments) for sym in model if sym.name == predicate_name]
+    return [intermediate_repr(sym.arguments) for sym in model if sym.name == predicate_name]
 
 
 class ErrorHandler:
@@ -772,8 +803,11 @@ def visit(node):
 
         # Load the file itself
         self.control.load(os.path.join(parent_dir, "concretize.lp"))
+        self.control.load(os.path.join(parent_dir, "heuristic.lp"))
         self.control.load(os.path.join(parent_dir, "os_compatibility.lp"))
         self.control.load(os.path.join(parent_dir, "display.lp"))
+        if not setup.concretize_everything:
+            self.control.load(os.path.join(parent_dir, "when_possible.lp"))
         timer.stop("load")
 
         # Grounding is the first step in the solve -- it turns our facts
@@ -801,6 +835,14 @@ def on_model(model):
 
         timer.start("solve")
         solve_result = self.control.solve(**solve_kwargs)
+
+        if solve_result.satisfiable and self._model_has_cycles(models):
+            tty.debug(f"cycles detected, falling back to slower algorithm [specs={specs}]")
+            self.control.load(os.path.join(parent_dir, "cycle_detection.lp"))
+            self.control.ground([("no_cycle", [])])
+            models.clear()
+            solve_result = self.control.solve(**solve_kwargs)
+
         timer.stop("solve")
 
         # once done, construct the solve result
@@ -836,7 +878,8 @@ def on_model(model):
             for sym in best_model:
                 if sym.name not in ("attr", "error", "opt_criterion"):
                     tty.debug(
-                        "UNKNOWN SYMBOL: %s(%s)" % (sym.name, ", ".join(stringify(sym.arguments)))
+                        "UNKNOWN SYMBOL: %s(%s)"
+                        % (sym.name, ", ".join(intermediate_repr(sym.arguments)))
                     )
 
         elif cores:
@@ -853,6 +896,26 @@ def on_model(model):
 
         return result, timer, self.control.statistics
 
+    def _model_has_cycles(self, models):
+        """Returns true if the best model has cycles in it"""
+        cycle_detection = clingo.Control()
+        parent_dir = pathlib.Path(__file__).parent
+        lp_file = parent_dir / "cycle_detection.lp"
+
+        min_cost, best_model = min(models)
+        with cycle_detection.backend() as backend:
+            for atom in best_model:
+                if atom.name == "attr" and str(atom.arguments[0]) == '"depends_on"':
+                    symbol = fn.depends_on(atom.arguments[1], atom.arguments[2])
+                    atom_id = backend.add_atom(symbol.symbol())
+                    backend.add_rule([atom_id], [], choice=False)
+
+            cycle_detection.load(str(lp_file))
+            cycle_detection.ground([("base", []), ("no_cycle", [])])
+            cycle_result = cycle_detection.solve()
+
+        return cycle_result.unsatisfiable
+
 
 class SpackSolverSetup:
     """Class to set up and run a Spack concretization solve."""
@@ -883,6 +946,10 @@ def __init__(self, tests=False):
 
         # id for dummy variables
         self._condition_id_counter = itertools.count()
+        self._trigger_id_counter = itertools.count()
+        self._trigger_cache = collections.defaultdict(dict)
+        self._effect_id_counter = itertools.count()
+        self._effect_cache = collections.defaultdict(dict)
 
         # Caches to optimize the setup phase of the solver
         self.target_specs_cache = None
@@ -919,15 +986,18 @@ def key_fn(version):
 
         for weight, declared_version in enumerate(most_to_least_preferred):
             self.gen.fact(
-                fn.version_declared(
-                    pkg.name, declared_version.version, weight, str(declared_version.origin)
+                fn.pkg_fact(
+                    pkg.name,
+                    fn.version_declared(
+                        declared_version.version, weight, str(declared_version.origin)
+                    ),
                 )
             )
 
         # Declare deprecated versions for this package, if any
         deprecated = self.deprecated_versions[pkg.name]
         for v in sorted(deprecated):
-            self.gen.fact(fn.deprecated_version(pkg.name, v))
+            self.gen.fact(fn.pkg_fact(pkg.name, fn.deprecated_version(v)))
 
     def spec_versions(self, spec):
         """Return list of clauses expressing spec's version constraints."""
@@ -956,11 +1026,14 @@ def target_ranges(self, spec, single_target_fn):
         return [fn.attr("node_target_satisfies", spec.name, target)]
 
     def conflict_rules(self, pkg):
-        default_msg = "{0} '{1}' conflicts with '{2}'"
-        no_constraint_msg = "{0} conflicts with '{1}'"
+        default_msg = "{0}: '{1}' conflicts with '{2}'"
+        no_constraint_msg = "{0}: conflicts with '{1}'"
         for trigger, constraints in pkg.conflicts.items():
             trigger_msg = "conflict trigger %s" % str(trigger)
-            trigger_id = self.condition(spack.spec.Spec(trigger), name=pkg.name, msg=trigger_msg)
+            trigger_spec = spack.spec.Spec(trigger)
+            trigger_id = self.condition(
+                trigger_spec, name=trigger_spec.name or pkg.name, msg=trigger_msg
+            )
 
             for constraint, conflict_msg in constraints:
                 if conflict_msg is None:
@@ -970,7 +1043,9 @@ def conflict_rules(self, pkg):
                         conflict_msg = default_msg.format(pkg.name, trigger, constraint)
                 constraint_msg = "conflict constraint %s" % str(constraint)
                 constraint_id = self.condition(constraint, name=pkg.name, msg=constraint_msg)
-                self.gen.fact(fn.conflict(pkg.name, trigger_id, constraint_id, conflict_msg))
+                self.gen.fact(
+                    fn.pkg_fact(pkg.name, fn.conflict(trigger_id, constraint_id, conflict_msg))
+                )
                 self.gen.newline()
 
     def compiler_facts(self):
@@ -1023,8 +1098,11 @@ def package_compiler_defaults(self, pkg):
 
         for i, compiler in enumerate(reversed(matches)):
             self.gen.fact(
-                fn.node_compiler_preference(
-                    pkg.name, compiler.spec.name, compiler.spec.version, -i * 100
+                fn.pkg_fact(
+                    pkg.name,
+                    fn.node_compiler_preference(
+                        compiler.spec.name, compiler.spec.version, -i * 100
+                    ),
                 )
             )
 
@@ -1114,12 +1192,65 @@ def pkg_rules(self, pkg, tests):
         self.gen.newline()
 
         # variants
+        self.variant_rules(pkg)
+
+        # conflicts
+        self.conflict_rules(pkg)
+
+        # default compilers for this package
+        self.package_compiler_defaults(pkg)
+
+        # virtuals
+        self.package_provider_rules(pkg)
+
+        # dependencies
+        self.package_dependencies_rules(pkg)
+
+        # virtual preferences
+        self.virtual_preferences(
+            pkg.name,
+            lambda v, p, i: self.gen.fact(fn.pkg_fact(pkg.name, fn.provider_preference(v, p, i))),
+        )
+
+        self.package_requirement_rules(pkg)
+
+        # trigger and effect tables
+        self.trigger_rules()
+        self.effect_rules()
+
+    def trigger_rules(self):
+        """Flushes all the trigger rules collected so far, and clears the cache."""
+        self.gen.h2("Trigger conditions")
+        for name in self._trigger_cache:
+            cache = self._trigger_cache[name]
+            for spec_str, (trigger_id, requirements) in cache.items():
+                self.gen.fact(fn.pkg_fact(name, fn.trigger_id(trigger_id)))
+                self.gen.fact(fn.pkg_fact(name, fn.trigger_msg(spec_str)))
+                for predicate in requirements:
+                    self.gen.fact(fn.condition_requirement(trigger_id, *predicate.args))
+                self.gen.newline()
+        self._trigger_cache.clear()
+
+    def effect_rules(self):
+        """Flushes all the effect rules collected so far, and clears the cache."""
+        self.gen.h2("Imposed requirements")
+        for name in self._effect_cache:
+            cache = self._effect_cache[name]
+            for spec_str, (effect_id, requirements) in cache.items():
+                self.gen.fact(fn.pkg_fact(name, fn.effect_id(effect_id)))
+                self.gen.fact(fn.pkg_fact(name, fn.effect_msg(spec_str)))
+                for predicate in requirements:
+                    self.gen.fact(fn.imposed_constraint(effect_id, *predicate.args))
+                self.gen.newline()
+        self._effect_cache.clear()
+
+    def variant_rules(self, pkg):
         for name, entry in sorted(pkg.variants.items()):
             variant, when = entry
 
             if spack.spec.Spec() in when:
                 # unconditional variant
-                self.gen.fact(fn.variant(pkg.name, name))
+                self.gen.fact(fn.pkg_fact(pkg.name, fn.variant(name)))
             else:
                 # conditional variant
                 for w in when:
@@ -1128,19 +1259,23 @@ def pkg_rules(self, pkg, tests):
                         msg += " when %s" % w
 
                     cond_id = self.condition(w, name=pkg.name, msg=msg)
-                    self.gen.fact(fn.variant_condition(cond_id, pkg.name, name))
+                    self.gen.fact(fn.pkg_fact(pkg.name, fn.conditional_variant(cond_id, name)))
 
             single_value = not variant.multi
             if single_value:
-                self.gen.fact(fn.variant_single_value(pkg.name, name))
+                self.gen.fact(fn.pkg_fact(pkg.name, fn.variant_single_value(name)))
                 self.gen.fact(
-                    fn.variant_default_value_from_package_py(pkg.name, name, variant.default)
+                    fn.pkg_fact(
+                        pkg.name, fn.variant_default_value_from_package_py(name, variant.default)
+                    )
                 )
             else:
                 spec_variant = variant.make_default()
                 defaults = spec_variant.value
                 for val in sorted(defaults):
-                    self.gen.fact(fn.variant_default_value_from_package_py(pkg.name, name, val))
+                    self.gen.fact(
+                        fn.pkg_fact(pkg.name, fn.variant_default_value_from_package_py(name, val))
+                    )
 
             values = variant.values
             if values is None:
@@ -1151,7 +1286,9 @@ def pkg_rules(self, pkg, tests):
                 for sid, s in enumerate(values.sets):
                     for value in s:
                         self.gen.fact(
-                            fn.variant_value_from_disjoint_sets(pkg.name, name, value, sid)
+                            fn.pkg_fact(
+                                pkg.name, fn.variant_value_from_disjoint_sets(name, value, sid)
+                            )
                         )
                     union.update(s)
                 values = union
@@ -1178,7 +1315,9 @@ def pkg_rules(self, pkg, tests):
                             msg="empty (total) conflict constraint",
                         )
                         msg = "variant {0}={1} is conditionally disabled".format(name, value)
-                        self.gen.fact(fn.conflict(pkg.name, trigger_id, constraint_id, msg))
+                        self.gen.fact(
+                            fn.pkg_fact(pkg.name, fn.conflict(trigger_id, constraint_id, msg))
+                        )
                     else:
                         imposed = spack.spec.Spec(value.when)
                         imposed.name = pkg.name
@@ -1189,32 +1328,13 @@ def pkg_rules(self, pkg, tests):
                             name=pkg.name,
                             msg="%s variant %s value %s when %s" % (pkg.name, name, value, when),
                         )
-                self.gen.fact(fn.variant_possible_value(pkg.name, name, value))
+                self.gen.fact(fn.pkg_fact(pkg.name, fn.variant_possible_value(name, value)))
 
             if variant.sticky:
-                self.gen.fact(fn.variant_sticky(pkg.name, name))
+                self.gen.fact(fn.pkg_fact(pkg.name, fn.variant_sticky(name)))
 
             self.gen.newline()
 
-        # conflicts
-        self.conflict_rules(pkg)
-
-        # default compilers for this package
-        self.package_compiler_defaults(pkg)
-
-        # virtuals
-        self.package_provider_rules(pkg)
-
-        # dependencies
-        self.package_dependencies_rules(pkg)
-
-        # virtual preferences
-        self.virtual_preferences(
-            pkg.name, lambda v, p, i: self.gen.fact(fn.pkg_provider_preference(pkg.name, v, p, i))
-        )
-
-        self.package_requirement_rules(pkg)
-
     def condition(self, required_spec, imposed_spec=None, name=None, msg=None, node=False):
         """Generate facts for a dependency or virtual provider condition.
 
@@ -1232,21 +1352,38 @@ def condition(self, required_spec, imposed_spec=None, name=None, msg=None, node=
         """
         named_cond = required_spec.copy()
         named_cond.name = named_cond.name or name
-        assert named_cond.name, "must provide name for anonymous condtions!"
+        assert named_cond.name, "must provide name for anonymous conditions!"
 
         # Check if we can emit the requirements before updating the condition ID counter.
         # In this way, if a condition can't be emitted but the exception is handled in the caller,
         # we won't emit partial facts.
-        requirements = self.spec_clauses(named_cond, body=True, required_from=name)
 
         condition_id = next(self._condition_id_counter)
-        self.gen.fact(fn.condition(condition_id, msg))
-        for pred in requirements:
-            self.gen.fact(fn.condition_requirement(condition_id, *pred.args))
+        self.gen.fact(fn.pkg_fact(named_cond.name, fn.condition(condition_id)))
+        self.gen.fact(fn.condition_reason(condition_id, msg))
 
-        if imposed_spec:
-            self.impose(condition_id, imposed_spec, node=node, name=name)
+        cache = self._trigger_cache[named_cond.name]
+        if named_cond not in cache:
+            trigger_id = next(self._trigger_id_counter)
+            requirements = self.spec_clauses(named_cond, body=True, required_from=name)
+            cache[named_cond] = (trigger_id, requirements)
+        trigger_id, requirements = cache[named_cond]
+        self.gen.fact(fn.pkg_fact(named_cond.name, fn.condition_trigger(condition_id, trigger_id)))
 
+        if not imposed_spec:
+            return condition_id
+
+        cache = self._effect_cache[named_cond.name]
+        if imposed_spec not in cache:
+            effect_id = next(self._effect_id_counter)
+            requirements = self.spec_clauses(imposed_spec, body=False, required_from=name)
+            if not node:
+                requirements = list(
+                    filter(lambda x: x.args[0] not in ("node", "virtual_node"), requirements)
+                )
+            cache[imposed_spec] = (effect_id, requirements)
+        effect_id, requirements = cache[imposed_spec]
+        self.gen.fact(fn.pkg_fact(named_cond.name, fn.condition_effect(condition_id, effect_id)))
         return condition_id
 
     def impose(self, condition_id, imposed_spec, node=True, name=None, body=False):
@@ -1259,13 +1396,19 @@ def impose(self, condition_id, imposed_spec, node=True, name=None, body=False):
 
     def package_provider_rules(self, pkg):
         for provider_name in sorted(set(s.name for s in pkg.provided.keys())):
-            self.gen.fact(fn.possible_provider(pkg.name, provider_name))
+            if provider_name not in self.possible_virtuals:
+                continue
+            self.gen.fact(fn.pkg_fact(pkg.name, fn.possible_provider(provider_name)))
 
         for provided, whens in pkg.provided.items():
+            if provided.name not in self.possible_virtuals:
+                continue
             for when in whens:
                 msg = "%s provides %s when %s" % (pkg.name, provided, when)
                 condition_id = self.condition(when, provided, pkg.name, msg)
-                self.gen.fact(fn.provider_condition(condition_id, when.name, provided.name))
+                self.gen.fact(
+                    fn.pkg_fact(when.name, fn.provider_condition(condition_id, provided.name))
+                )
             self.gen.newline()
 
     def package_dependencies_rules(self, pkg):
@@ -1289,9 +1432,13 @@ def package_dependencies_rules(self, pkg):
                 msg = "%s depends on %s" % (pkg.name, dep.spec.name)
                 if cond != spack.spec.Spec():
                     msg += " when %s" % cond
+                else:
+                    pass
 
                 condition_id = self.condition(cond, dep.spec, pkg.name, msg)
-                self.gen.fact(fn.dependency_condition(condition_id, pkg.name, dep.spec.name))
+                self.gen.fact(
+                    fn.pkg_fact(pkg.name, fn.dependency_condition(condition_id, dep.spec.name))
+                )
 
                 for t in sorted(deptypes):
                     # there is a declared dependency of type t
@@ -1328,7 +1475,7 @@ def provider_requirements(self):
             "Internal Error: possible_virtuals is not populated. Please report to the spack"
             " maintainers"
         )
-        packages_yaml = spack.config.config.get("packages")
+        packages_yaml = spack.config.CONFIG.get("packages")
         assert self.possible_virtuals is not None, msg
         for virtual_str in sorted(self.possible_virtuals):
             requirements = packages_yaml.get(virtual_str, {}).get("require", [])
@@ -1336,6 +1483,8 @@ def provider_requirements(self):
                 virtual_str, requirements, kind=RequirementKind.VIRTUAL
             )
             self.emit_facts_from_requirement_rules(rules)
+            self.trigger_rules()
+            self.effect_rules()
 
     def emit_facts_from_requirement_rules(self, rules: List[RequirementRule]):
         """Generate facts to enforce requirements.
@@ -1416,7 +1565,7 @@ def external_packages(self):
                 continue
 
             # This package does not appear in any repository
-            if pkg_name not in spack.repo.path:
+            if pkg_name not in spack.repo.PATH:
                 continue
 
             self.gen.h2("External package: {0}".format(pkg_name))
@@ -1449,10 +1598,12 @@ def external_packages(self):
             for local_idx, spec in enumerate(external_specs):
                 msg = "%s available as external when satisfying %s" % (spec.name, spec)
                 condition_id = self.condition(spec, msg=msg)
-                self.gen.fact(fn.possible_external(condition_id, pkg_name, local_idx))
+                self.gen.fact(fn.pkg_fact(pkg_name, fn.possible_external(condition_id, local_idx)))
                 self.possible_versions[spec.name].add(spec.version)
                 self.gen.newline()
 
+            self.trigger_rules()
+
     def preferred_variants(self, pkg_name):
         """Facts on concretization preferences, as read from packages.yaml"""
         preferences = spack.package_prefs.PackagePrefs
@@ -1495,7 +1646,9 @@ def target_preferences(self, pkg_name):
             if str(preferred.architecture.target) == best_default and i != 0:
                 offset = 100
             self.gen.fact(
-                fn.target_weight(pkg_name, str(preferred.architecture.target), i + offset)
+                fn.pkg_fact(
+                    pkg_name, fn.target_weight(str(preferred.architecture.target), i + offset)
+                )
             )
 
     def spec_clauses(self, *args, **kwargs):
@@ -1598,7 +1751,7 @@ class Body:
                 if not spec.concrete:
                     reserved_names = spack.directives.reserved_names
                     if not spec.virtual and vname not in reserved_names:
-                        pkg_cls = spack.repo.path.get_pkg_class(spec.name)
+                        pkg_cls = spack.repo.PATH.get_pkg_class(spec.name)
                         try:
                             variant_def, _ = pkg_cls.variants[vname]
                         except KeyError:
@@ -1606,7 +1759,7 @@ class Body:
                             raise RuntimeError(msg.format(vname, spec.name))
                         else:
                             variant_def.validate_or_raise(
-                                variant, spack.repo.path.get_pkg_class(spec.name)
+                                variant, spack.repo.PATH.get_pkg_class(spec.name)
                             )
 
                 clauses.append(f.variant_value(spec.name, vname, value))
@@ -1678,7 +1831,7 @@ class Body:
                                 except spack.repo.UnknownNamespaceError:
                                     # Try to look up the package of the same name and use its
                                     # providers. This is as good as we can do without edge info.
-                                    pkg_class = spack.repo.path.get_pkg_class(dep.name)
+                                    pkg_class = spack.repo.PATH.get_pkg_class(dep.name)
                                     spec = spack.spec.Spec(f"{dep.name}@{dep.version}")
                                     pkg = pkg_class(spec)
 
@@ -1724,7 +1877,7 @@ def build_version_dict(self, possible_pkgs):
         packages_yaml = spack.config.get("packages")
         packages_yaml = _normalize_packages_yaml(packages_yaml)
         for pkg_name in possible_pkgs:
-            pkg_cls = spack.repo.path.get_pkg_class(pkg_name)
+            pkg_cls = spack.repo.PATH.get_pkg_class(pkg_name)
 
             # All the versions from the corresponding package.py file. Since concepts
             # like being a "develop" version or being preferred exist only at a
@@ -1755,7 +1908,7 @@ def key_fn(item):
             # specs will be computed later
             version_preferences = packages_yaml.get(pkg_name, {}).get("version", [])
             version_defs = []
-            pkg_class = spack.repo.path.get_pkg_class(pkg_name)
+            pkg_class = spack.repo.PATH.get_pkg_class(pkg_name)
             for vstr in version_preferences:
                 v = vn.ver(vstr)
                 if isinstance(v, vn.GitVersion):
@@ -2041,11 +2194,11 @@ def define_version_constraints(self):
             # generate facts for each package constraint and the version
             # that satisfies it
             for v in sorted(v for v in self.possible_versions[pkg_name] if v.satisfies(versions)):
-                self.gen.fact(fn.version_satisfies(pkg_name, versions, v))
+                self.gen.fact(fn.pkg_fact(pkg_name, fn.version_satisfies(versions, v)))
 
             self.gen.newline()
 
-    def define_virtual_constraints(self):
+    def collect_virtual_constraints(self):
         """Define versions for constraints on virtuals.
 
         Must be called before define_version_constraints().
@@ -2053,7 +2206,7 @@ def define_virtual_constraints(self):
         # aggregate constraints into per-virtual sets
         constraint_map = collections.defaultdict(lambda: set())
         for pkg_name, versions in self.version_constraints:
-            if not spack.repo.path.is_virtual(pkg_name):
+            if not spack.repo.PATH.is_virtual(pkg_name):
                 continue
             constraint_map[pkg_name].add(versions)
 
@@ -2131,7 +2284,7 @@ def define_variant_values(self):
         # spec_clauses(). We might want to order these facts by pkg and name
         # if we are debugging.
         for pkg, variant, value in self.variant_values_from_specs:
-            self.gen.fact(fn.variant_possible_value(pkg, variant, value))
+            self.gen.fact(fn.pkg_fact(pkg, fn.variant_possible_value(variant, value)))
 
     def _facts_from_concrete_spec(self, spec, possible):
         # tell the solver about any installed packages that could
@@ -2141,7 +2294,7 @@ def _facts_from_concrete_spec(self, spec, possible):
             self.reusable_and_possible[h] = spec
             try:
                 # Only consider installed packages for repo we know
-                spack.repo.path.get(spec)
+                spack.repo.PATH.get(spec)
             except (spack.repo.UnknownNamespaceError, spack.repo.UnknownPackageError):
                 return
 
@@ -2191,20 +2344,19 @@ def setup(self, driver, specs, reuse=None):
 
         # get list of all possible dependencies
         self.possible_virtuals = set(x.name for x in specs if x.virtual)
-        possible = spack.package_base.possible_dependencies(
-            *specs, virtuals=self.possible_virtuals, deptype=spack.dependency.all_deptypes
-        )
+
+        node_counter = _create_counter(specs, tests=self.tests)
+        self.possible_virtuals = node_counter.possible_virtuals()
+        self.pkgs = node_counter.possible_dependencies()
 
         # Fail if we already know an unreachable node is requested
         for spec in specs:
             missing_deps = [
-                str(d) for d in spec.traverse() if d.name not in possible and not d.virtual
+                str(d) for d in spec.traverse() if d.name not in self.pkgs and not d.virtual
             ]
             if missing_deps:
                 raise spack.spec.InvalidDependencyError(spec.name, missing_deps)
 
-        self.pkgs = set(possible)
-
         # driver is used by all the functions below to add facts and
         # rules to generate an ASP program.
         self.gen = driver
@@ -2228,13 +2380,16 @@ def setup(self, driver, specs, reuse=None):
         self.possible_compilers = self.generate_possible_compilers(specs)
 
         self.gen.h1("Concrete input spec definitions")
-        self.define_concrete_input_specs(specs, possible)
+        self.define_concrete_input_specs(specs, self.pkgs)
 
         if reuse:
             self.gen.h1("Reusable specs")
             self.gen.fact(fn.optimize_for_reuse())
             for reusable_spec in reuse:
-                self._facts_from_concrete_spec(reusable_spec, possible)
+                self._facts_from_concrete_spec(reusable_spec, self.pkgs)
+
+        self.gen.h1("Generic statements on possible packages")
+        node_counter.possible_packages_facts(self.gen, fn)
 
         self.gen.h1("Possible flags on nodes")
         for flag in spack.spec.FlagMap.valid_compiler_flags():
@@ -2255,7 +2410,7 @@ def setup(self, driver, specs, reuse=None):
         self.external_packages()
 
         # traverse all specs and packages to build dict of possible versions
-        self.build_version_dict(possible)
+        self.build_version_dict(self.pkgs)
         self.add_concrete_versions_from_specs(specs, Provenance.SPEC)
         self.add_concrete_versions_from_specs(dev_specs, Provenance.DEV_SPEC)
 
@@ -2270,9 +2425,12 @@ def setup(self, driver, specs, reuse=None):
             self.preferred_variants(pkg)
             self.target_preferences(pkg)
 
+        self.gen.h1("Develop specs")
         # Inject dev_path from environment
         for ds in dev_specs:
             self.condition(spack.spec.Spec(ds.name), ds, msg="%s is a develop spec" % ds.name)
+            self.trigger_rules()
+            self.effect_rules()
 
         self.gen.h1("Spec Constraints")
         self.literal_specs(specs)
@@ -2280,10 +2438,8 @@ def setup(self, driver, specs, reuse=None):
         self.gen.h1("Variant Values defined in specs")
         self.define_variant_values()
 
-        self.gen.h1("Virtual Constraints")
-        self.define_virtual_constraints()
-
         self.gen.h1("Version Constraints")
+        self.collect_virtual_constraints()
         self.define_version_constraints()
 
         self.gen.h1("Compiler Version Constraints")
@@ -2305,8 +2461,8 @@ def literal_specs(self, specs):
                         fn.literal(idx, "variant_default_value_from_cli", *clause.args[1:])
                     )
 
-        if self.concretize_everything:
-            self.gen.fact(fn.concretize_everything())
+            if self.concretize_everything:
+                self.gen.fact(fn.solve_literal(idx))
 
     def _get_versioned_specs_from_pkg_requirements(self):
         """If package requirements mention versions that are not mentioned
@@ -2366,7 +2522,7 @@ def _specs_from_requires(self, pkg_name, section):
             # Prefer spec's name if it exists, in case the spec is
             # requiring a specific implementation inside of a virtual section
             # e.g. packages:mpi:require:openmpi@4.0.1
-            pkg_class = spack.repo.path.get_pkg_class(spec.name or pkg_name)
+            pkg_class = spack.repo.PATH.get_pkg_class(spec.name or pkg_name)
             satisfying_versions = self._check_for_defined_matching_versions(
                 pkg_class, spec.versions
             )
@@ -2401,6 +2557,16 @@ class SpecBuilder:
         )
     )
 
+    @staticmethod
+    def make_node(*, pkg: str) -> NodeArgument:
+        """Given a package name, returns the string representation of the "min_dupe_id" node in
+        the ASP encoding.
+
+        Args:
+            pkg: name of a package
+        """
+        return NodeArgument(id="0", pkg=pkg)
+
     def __init__(self, specs, hash_lookup=None):
         self._specs = {}
         self._result = None
@@ -2413,101 +2579,105 @@ def __init__(self, specs, hash_lookup=None):
         # from this dictionary during reconstruction
         self._hash_lookup = hash_lookup or {}
 
-    def hash(self, pkg, h):
-        if pkg not in self._specs:
-            self._specs[pkg] = self._hash_lookup[h]
-        self._hash_specs.append(pkg)
+    def hash(self, node, h):
+        if node not in self._specs:
+            self._specs[node] = self._hash_lookup[h]
+        self._hash_specs.append(node)
 
-    def node(self, pkg):
-        if pkg not in self._specs:
-            self._specs[pkg] = spack.spec.Spec(pkg)
+    def node(self, node):
+        if node not in self._specs:
+            self._specs[node] = spack.spec.Spec(node.pkg)
 
-    def _arch(self, pkg):
-        arch = self._specs[pkg].architecture
+    def _arch(self, node):
+        arch = self._specs[node].architecture
         if not arch:
             arch = spack.spec.ArchSpec()
-            self._specs[pkg].architecture = arch
+            self._specs[node].architecture = arch
         return arch
 
-    def node_platform(self, pkg, platform):
-        self._arch(pkg).platform = platform
+    def node_platform(self, node, platform):
+        self._arch(node).platform = platform
 
-    def node_os(self, pkg, os):
-        self._arch(pkg).os = os
+    def node_os(self, node, os):
+        self._arch(node).os = os
 
-    def node_target(self, pkg, target):
-        self._arch(pkg).target = target
+    def node_target(self, node, target):
+        self._arch(node).target = target
 
-    def variant_value(self, pkg, name, value):
+    def variant_value(self, node, name, value):
         # FIXME: is there a way not to special case 'dev_path' everywhere?
         if name == "dev_path":
-            self._specs[pkg].variants.setdefault(
+            self._specs[node].variants.setdefault(
                 name, spack.variant.SingleValuedVariant(name, value)
             )
             return
 
         if name == "patches":
-            self._specs[pkg].variants.setdefault(
+            self._specs[node].variants.setdefault(
                 name, spack.variant.MultiValuedVariant(name, value)
             )
             return
 
-        self._specs[pkg].update_variant_validate(name, value)
+        self._specs[node].update_variant_validate(name, value)
 
-    def version(self, pkg, version):
-        self._specs[pkg].versions = vn.VersionList([vn.Version(version)])
+    def version(self, node, version):
+        self._specs[node].versions = vn.VersionList([vn.Version(version)])
 
-    def node_compiler_version(self, pkg, compiler, version):
-        self._specs[pkg].compiler = spack.spec.CompilerSpec(compiler)
-        self._specs[pkg].compiler.versions = vn.VersionList([vn.Version(version)])
+    def node_compiler_version(self, node, compiler, version):
+        self._specs[node].compiler = spack.spec.CompilerSpec(compiler)
+        self._specs[node].compiler.versions = vn.VersionList([vn.Version(version)])
 
-    def node_flag_compiler_default(self, pkg):
-        self._flag_compiler_defaults.add(pkg)
+    def node_flag_compiler_default(self, node):
+        self._flag_compiler_defaults.add(node)
 
-    def node_flag(self, pkg, flag_type, flag):
-        self._specs[pkg].compiler_flags.add_flag(flag_type, flag, False)
+    def node_flag(self, node, flag_type, flag):
+        self._specs[node].compiler_flags.add_flag(flag_type, flag, False)
 
-    def node_flag_source(self, pkg, flag_type, source):
-        self._flag_sources[(pkg, flag_type)].add(source)
+    def node_flag_source(self, node, flag_type, source):
+        self._flag_sources[(node, flag_type)].add(source)
 
-    def no_flags(self, pkg, flag_type):
-        self._specs[pkg].compiler_flags[flag_type] = []
+    def no_flags(self, node, flag_type):
+        self._specs[node].compiler_flags[flag_type] = []
 
-    def external_spec_selected(self, pkg, idx):
+    def external_spec_selected(self, node, idx):
         """This means that the external spec and index idx
         has been selected for this package.
         """
+
         packages_yaml = spack.config.get("packages")
         packages_yaml = _normalize_packages_yaml(packages_yaml)
-        spec_info = packages_yaml[pkg]["externals"][int(idx)]
-        self._specs[pkg].external_path = spec_info.get("prefix", None)
-        self._specs[pkg].external_modules = spack.spec.Spec._format_module_list(
+        spec_info = packages_yaml[node.pkg]["externals"][int(idx)]
+        self._specs[node].external_path = spec_info.get("prefix", None)
+        self._specs[node].external_modules = spack.spec.Spec._format_module_list(
             spec_info.get("modules", None)
         )
-        self._specs[pkg].extra_attributes = spec_info.get("extra_attributes", {})
+        self._specs[node].extra_attributes = spec_info.get("extra_attributes", {})
 
         # If this is an extension, update the dependencies to include the extendee
-        package = self._specs[pkg].package_class(self._specs[pkg])
+        package = self._specs[node].package_class(self._specs[node])
         extendee_spec = package.extendee_spec
+
         if extendee_spec:
-            package.update_external_dependencies(self._specs.get(extendee_spec.name, None))
+            extendee_node = SpecBuilder.make_node(pkg=extendee_spec.name)
+            package.update_external_dependencies(self._specs.get(extendee_node, None))
 
-    def depends_on(self, pkg, dep, type):
-        dependencies = self._specs[pkg].edges_to_dependencies(name=dep)
+    def depends_on(self, parent_node, dependency_node, type):
+        dependency_spec = self._specs[dependency_node]
+        edges = self._specs[parent_node].edges_to_dependencies(name=dependency_spec.name)
+        edges = [x for x in edges if id(x.spec) == id(dependency_spec)]
 
-        # TODO: assertion to be removed when cross-compilation is handled correctly
-        msg = "Current solver does not handle multiple dependency edges of the same name"
-        assert len(dependencies) < 2, msg
-
-        if not dependencies:
-            self._specs[pkg].add_dependency_edge(self._specs[dep], deptypes=(type,), virtuals=())
+        if not edges:
+            self._specs[parent_node].add_dependency_edge(
+                self._specs[dependency_node], deptypes=(type,), virtuals=()
+            )
         else:
-            # TODO: This assumes that each solve unifies dependencies
-            dependencies[0].update_deptypes(deptypes=(type,))
+            edges[0].update_deptypes(deptypes=(type,))
 
-    def virtual_on_edge(self, pkg, provider, virtual):
-        dependencies = self._specs[pkg].edges_to_dependencies(name=provider)
-        assert len(dependencies) == 1
+    def virtual_on_edge(self, parent_node, provider_node, virtual):
+        dependencies = self._specs[parent_node].edges_to_dependencies(name=(provider_node.pkg))
+        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,))
 
     def reorder_flags(self):
@@ -2537,19 +2707,23 @@ def reorder_flags(self):
 
                 # order is determined by the  DAG. A spec's flags come after any of its ancestors
                 # on the compile line
-                source_key = (spec.name, flag_type)
+                node = SpecBuilder.make_node(pkg=spec.name)
+                source_key = (node, flag_type)
                 if source_key in self._flag_sources:
-                    order = [s.name for s in spec.traverse(order="post", direction="parents")]
+                    order = [
+                        SpecBuilder.make_node(pkg=s.name)
+                        for s in spec.traverse(order="post", direction="parents")
+                    ]
                     sorted_sources = sorted(
                         self._flag_sources[source_key], key=lambda s: order.index(s)
                     )
 
                     # add flags from each source, lowest to highest precedence
-                    for name in sorted_sources:
+                    for node in sorted_sources:
                         all_src_flags = list()
-                        per_pkg_sources = [self._specs[name]]
-                        if name in cmd_specs:
-                            per_pkg_sources.append(cmd_specs[name])
+                        per_pkg_sources = [self._specs[node]]
+                        if node.pkg in cmd_specs:
+                            per_pkg_sources.append(cmd_specs[node.pkg])
                         for source in per_pkg_sources:
                             all_src_flags.extend(source.compiler_flags.get(flag_type, []))
                         extend_flag_list(from_sources, all_src_flags)
@@ -2620,14 +2794,15 @@ def build_specs(self, function_tuples):
             # solving but don't construct anything. Do not ignore error
             # predicates on virtual packages.
             if name != "error":
-                pkg = args[0]
-                if spack.repo.path.is_virtual(pkg):
+                node = args[0]
+                pkg = node.pkg
+                if spack.repo.PATH.is_virtual(pkg):
                     continue
 
                 # if we've already gotten a concrete spec for this pkg,
                 # do not bother calling actions on it except for node_flag_source,
                 # since node_flag_source is tracking information not in the spec itself
-                spec = self._specs.get(pkg)
+                spec = self._specs.get(args[0])
                 if spec and spec.concrete:
                     if name != "node_flag_source":
                         continue
@@ -2639,16 +2814,18 @@ def build_specs(self, function_tuples):
         for spec in self._specs.values():
             if spec.namespace:
                 continue
-            repo = spack.repo.path.repo_for_pkg(spec)
+            repo = spack.repo.PATH.repo_for_pkg(spec)
             spec.namespace = repo.namespace
 
         # fix flags after all specs are constructed
         self.reorder_flags()
 
+        # cycle detection
+        roots = [spec.root for spec in self._specs.values() if not spec.root.installed]
+
         # inject patches -- note that we' can't use set() to unique the
         # roots here, because the specs aren't complete, and the hash
         # function will loop forever.
-        roots = [spec.root for spec in self._specs.values() if not spec.root.installed]
         roots = dict((id(r), r) for r in roots)
         for root in roots.values():
             spack.spec.Spec.inject_patches_variant(root)
@@ -2768,7 +2945,7 @@ def solve(self, specs, out=None, timers=False, stats=False, tests=False, setup_o
         Arguments:
           specs (list): List of ``Spec`` objects to solve for.
           out: Optionally write the generate ASP program to a file-like object.
-          timers (bool): Print out coarse fimers for different solve phases.
+          timers (bool): Print out coarse timers for different solve phases.
           stats (bool): Print out detailed stats from clingo.
           tests (bool or tuple): If True, concretize test dependencies for all packages.
             If a tuple of package names, concretize test dependencies for named

lib/spack/spack/solver/counter.py

@@ -0,0 +1,159 @@
+# Copyright 2013-2023 Lawrence Livermore National Security, LLC and other
+# Spack Project Developers. See the top-level COPYRIGHT file for details.
+#
+# SPDX-License-Identifier: (Apache-2.0 OR MIT)
+import collections
+from typing import List, Set, Tuple
+
+import spack.dependency
+import spack.package_base
+
+PossibleDependencies = Set[str]
+
+
+class Counter:
+    """Computes the possible packages and the maximum number of duplicates
+    allowed for each of them.
+
+    Args:
+        specs: abstract specs to concretize
+        tests: if True, add test dependencies to the list of possible packages
+    """
+
+    def __init__(self, specs: List["spack.spec.Spec"], tests: bool) -> None:
+        self.specs = specs
+
+        self.link_run_types: Tuple[str, ...] = ("link", "run", "test")
+        self.all_types: Tuple[str, ...] = spack.dependency.all_deptypes
+        if not tests:
+            self.link_run_types = ("link", "run")
+            self.all_types = ("link", "run", "build")
+
+        self._possible_dependencies: PossibleDependencies = set()
+        self._possible_virtuals: Set[str] = set(x.name for x in specs if x.virtual)
+
+    def possible_dependencies(self) -> PossibleDependencies:
+        """Returns the list of possible dependencies"""
+        self.ensure_cache_values()
+        return self._possible_dependencies
+
+    def possible_virtuals(self) -> Set[str]:
+        """Returns the list of possible virtuals"""
+        self.ensure_cache_values()
+        return self._possible_virtuals
+
+    def ensure_cache_values(self) -> None:
+        """Ensure the cache values have been computed"""
+        if self._possible_dependencies:
+            return
+        self._compute_cache_values()
+
+    def possible_packages_facts(self, gen: "spack.solver.asp.PyclingoDriver", fn) -> None:
+        """Emit facts associated with the possible packages"""
+        raise NotImplementedError("must be implemented by derived classes")
+
+    def _compute_cache_values(self):
+        raise NotImplementedError("must be implemented by derived classes")
+
+
+class NoDuplicatesCounter(Counter):
+    def _compute_cache_values(self):
+        result = spack.package_base.possible_dependencies(
+            *self.specs, virtuals=self._possible_virtuals, deptype=self.all_types
+        )
+        self._possible_dependencies = set(result)
+
+    def possible_packages_facts(self, gen, fn):
+        gen.h2("Maximum number of nodes (packages)")
+        for package_name in sorted(self.possible_dependencies()):
+            gen.fact(fn.max_dupes(package_name, 1))
+        gen.newline()
+        gen.h2("Maximum number of nodes (virtual packages)")
+        for package_name in sorted(self.possible_virtuals()):
+            gen.fact(fn.max_dupes(package_name, 1))
+        gen.newline()
+        gen.h2("Possible package in link-run subDAG")
+        for name in sorted(self.possible_dependencies()):
+            gen.fact(fn.possible_in_link_run(name))
+        gen.newline()
+
+
+class MinimalDuplicatesCounter(NoDuplicatesCounter):
+    def __init__(self, specs, tests):
+        super().__init__(specs, tests)
+        self._link_run: PossibleDependencies = set()
+        self._direct_build: PossibleDependencies = set()
+        self._total_build: PossibleDependencies = set()
+        self._link_run_virtuals: Set[str] = set()
+
+    def _compute_cache_values(self):
+        self._link_run = set(
+            spack.package_base.possible_dependencies(
+                *self.specs, virtuals=self._possible_virtuals, deptype=self.link_run_types
+            )
+        )
+        self._link_run_virtuals.update(self._possible_virtuals)
+        for x in self._link_run:
+            current = spack.repo.PATH.get_pkg_class(x).dependencies_of_type("build")
+            self._direct_build.update(current)
+
+        self._total_build = set(
+            spack.package_base.possible_dependencies(
+                *self._direct_build, virtuals=self._possible_virtuals, deptype=self.all_types
+            )
+        )
+        self._possible_dependencies = set(self._link_run) | set(self._total_build)
+
+    def possible_packages_facts(self, gen, fn):
+        build_tools = set(spack.repo.PATH.packages_with_tags("build-tools"))
+        gen.h2("Packages with at most a single node")
+        for package_name in sorted(self.possible_dependencies() - build_tools):
+            gen.fact(fn.max_dupes(package_name, 1))
+        gen.newline()
+
+        gen.h2("Packages with at multiple possible nodes (build-tools)")
+        for package_name in sorted(self.possible_dependencies() & build_tools):
+            gen.fact(fn.max_dupes(package_name, 2))
+            gen.fact(fn.multiple_unification_sets(package_name))
+        gen.newline()
+
+        gen.h2("Maximum number of nodes (virtual packages)")
+        for package_name in sorted(self.possible_virtuals()):
+            gen.fact(fn.max_dupes(package_name, 1))
+        gen.newline()
+
+        gen.h2("Possible package in link-run subDAG")
+        for name in sorted(self._link_run):
+            gen.fact(fn.possible_in_link_run(name))
+        gen.newline()
+
+
+class FullDuplicatesCounter(MinimalDuplicatesCounter):
+    def possible_packages_facts(self, gen, fn):
+        build_tools = set(spack.repo.PATH.packages_with_tags("build-tools"))
+        counter = collections.Counter(
+            list(self._link_run) + list(self._total_build) + list(self._direct_build)
+        )
+        gen.h2("Maximum number of nodes")
+        for pkg, count in sorted(counter.items(), key=lambda x: (x[1], x[0])):
+            count = min(count, 2)
+            gen.fact(fn.max_dupes(pkg, count))
+        gen.newline()
+
+        gen.h2("Build unification sets ")
+        for name in sorted(self.possible_dependencies() & build_tools):
+            gen.fact(fn.multiple_unification_sets(name))
+        gen.newline()
+
+        gen.h2("Possible package in link-run subDAG")
+        for name in sorted(self._link_run):
+            gen.fact(fn.possible_in_link_run(name))
+        gen.newline()
+
+        counter = collections.Counter(
+            list(self._link_run_virtuals) + list(self._possible_virtuals)
+        )
+        gen.h2("Maximum number of virtual nodes")
+        for pkg, count in sorted(counter.items(), key=lambda x: (x[1], x[0])):
+            gen.fact(fn.max_dupes(pkg, count))
+        gen.newline()

lib/spack/spack/solver/cycle_detection.lp

@@ -0,0 +1,21 @@
+% Copyright 2013-2023 Lawrence Livermore National Security, LLC and other
+% Spack Project Developers. See the top-level COPYRIGHT file for details.
+%
+% SPDX-License-Identifier: (Apache-2.0 OR MIT)
+
+%=============================================================================
+% Avoid cycles in the DAG
+%
+% Some combinations of conditional dependencies can result in cycles;
+% this ensures that we solve around them. Note that these rules are quite
+% demanding on both grounding and solving, since they need to compute and
+% consider all possible paths between pair of nodes.
+%=============================================================================
+
+
+#program no_cycle.
+path(Parent, Child) :- depends_on(Parent, Child).
+path(Parent, Descendant) :- path(Parent, A), depends_on(A, Descendant).
+:- path(A, A).
+
+#defined depends_on/2.

lib/spack/spack/solver/heuristic.lp

@@ -0,0 +1,44 @@
+% Copyright 2013-2023 Lawrence Livermore National Security, LLC and other
+% Spack Project Developers. See the top-level COPYRIGHT file for details.
+%
+% SPDX-License-Identifier: (Apache-2.0 OR MIT)
+
+%=============================================================================
+% Heuristic to speed-up solves
+%=============================================================================
+
+
+%-----------------
+% Domain heuristic
+%-----------------
+#heuristic attr("hash", node(0, Package), Hash) : literal(_, "root", Package). [45, init]
+#heuristic attr("root", node(0, Package)) : literal(_, "root", Package). [45, true]
+#heuristic attr("node", node(0, Package)) : literal(_, "root", Package). [45, true]
+#heuristic attr("node", node(0, Package)) : literal(_, "node", Package). [45, true]
+
+% Root node
+#heuristic attr("version", node(0, Package), Version) : pkg_fact(Package, version_declared(Version, 0)), attr("root", node(0, Package)). [35, true]
+#heuristic version_weight(node(0, Package), 0) : pkg_fact(Package, version_declared(Version, 0)), attr("root", node(0, Package)). [35, true]
+#heuristic attr("variant_value", node(0, Package), Variant, Value) : variant_default_value(Package, Variant, Value), attr("root", node(0, Package)). [35, true]
+#heuristic attr("node_target", node(0, Package), Target) : pkg_fact(Package, target_weight(Target, 0)), attr("root", node(0, Package)). [35, true]
+#heuristic node_target_weight(node(0, Package), 0) : attr("root", node(0, Package)). [35, true]
+#heuristic node_compiler(node(0, Package), CompilerID) : default_compiler_preference(ID, 0), compiler_id(ID), attr("root", node(0, Package)). [35, true]
+
+% Providers
+#heuristic attr("node", node(0, Package)) : default_provider_preference(Virtual, Package, 0), possible_in_link_run(Package). [30, true]
+
+% node(ID, _)
+#heuristic attr("version", node(ID, Package), Version) : pkg_fact(Package, version_declared(Version, ID)), attr("node", node(ID, Package)). [25-5*ID, true]
+#heuristic version_weight(node(ID, Package), ID) : pkg_fact(Package, version_declared(Version, ID)), attr("node", node(ID, Package)). [25-5*ID, true]
+#heuristic attr("variant_value", node(ID, Package), Variant, Value) : variant_default_value(Package, Variant, Value), attr("node", node(ID, Package)). [25-5*ID, true]
+#heuristic attr("node_target", node(ID, Package), Target) : pkg_fact(Package, target_weight(Target, ID)), attr("node", node(ID, Package)). [25-5*ID, true]
+#heuristic node_target_weight(node(ID, Package), ID) : attr("node", node(ID, Package)). [25-5*ID, true]
+#heuristic node_compiler(node(ID, Package), CompilerID) : default_compiler_preference(ID, ID), compiler_id(ID), attr("node", node(ID, Package)). [25-5*ID, true]
+
+% node(ID, _), split build dependencies
+#heuristic attr("version", node(ID, Package), Version) : pkg_fact(Package, version_declared(Version, ID)), attr("node", node(ID, Package)), multiple_unification_sets(Package). [25, true]
+#heuristic version_weight(node(ID, Package), ID) : pkg_fact(Package, version_declared(Version, ID)), attr("node", node(ID, Package)), multiple_unification_sets(Package). [25, true]
+#heuristic attr("variant_value", node(ID, Package), Variant, Value) : variant_default_value(Package, Variant, Value), attr("node", node(ID, Package)), multiple_unification_sets(Package). [25, true]
+#heuristic attr("node_target", node(ID, Package), Target) : pkg_fact(Package, target_weight(Target, ID)), attr("node", node(ID, Package)), multiple_unification_sets(Package). [25, true]
+#heuristic node_target_weight(node(ID, Package), ID) : attr("node", node(ID, Package)), multiple_unification_sets(Package). [25, true]
+#heuristic node_compiler(node(ID, Package), CompilerID) : default_compiler_preference(ID, ID), compiler_id(ID), attr("node", node(ID, Package)), multiple_unification_sets(Package). [25, true]

lib/spack/spack/solver/os_compatibility.lp

@@ -3,9 +3,11 @@
 %
 % SPDX-License-Identifier: (Apache-2.0 OR MIT)
 
+%=============================================================================
 % OS compatibility rules for reusing solves.
 % os_compatible(RecentOS, OlderOS)
 % OlderOS binaries can be used on RecentOS
+%=============================================================================
 
 % macOS
 os_compatible("monterey", "bigsur").

lib/spack/spack/solver/when_possible.lp

@@ -0,0 +1,27 @@
+% Copyright 2013-2023 Lawrence Livermore National Security, LLC and other
+% Spack Project Developers. See the top-level COPYRIGHT file for details.
+%
+% SPDX-License-Identifier: (Apache-2.0 OR MIT)
+
+%=============================================================================
+% Minimize the number of literals that are not solved
+%
+% This minimization is used for the "when_possible" concretization mode,
+% otherwise we assume that all literals must be solved.
+%=============================================================================
+
+% Give clingo the choice to solve an input spec or not
+{ solve_literal(ID) } :- literal(ID).
+literal_not_solved(ID) :- not solve_literal(ID), literal(ID).
+
+% Make a problem with "zero literals solved" unsat. This is to trigger
+% looking for solutions to the ASP problem with "errors", which results
+% in better reporting for users. See #30669 for details.
+1 { solve_literal(ID) : literal(ID) }.
+
+opt_criterion(300, "number of input specs not concretized").
+#minimize{ 0@300: #true }.
+#minimize { 1@300,ID : literal_not_solved(ID) }.
+
+#heuristic literal_solved(ID) : literal(ID). [1, sign]
+#heuristic literal_solved(ID) : literal(ID). [50, init]

lib/spack/spack/spec.py

@@ -1299,7 +1299,7 @@ def __init__(self, spec, name, query_parameters):
         original_spec = getattr(spec, "wrapped_obj", spec)
         self.wrapped_obj = original_spec
         self.token = original_spec, name, query_parameters
-        is_virtual = spack.repo.path.is_virtual(name)
+        is_virtual = spack.repo.PATH.is_virtual(name)
         self.last_query = QueryState(
             name=name, extra_parameters=query_parameters, isvirtual=is_virtual
         )
@@ -1733,7 +1733,7 @@ def package(self):
             self.name
         )
         if not self._package:
-            self._package = spack.repo.path.get(self)
+            self._package = spack.repo.PATH.get(self)
         return self._package
 
     @property
@@ -1741,11 +1741,11 @@ def package_class(self):
         """Internal package call gets only the class object for a package.
         Use this to just get package metadata.
         """
-        return spack.repo.path.get_pkg_class(self.fullname)
+        return spack.repo.PATH.get_pkg_class(self.fullname)
 
     @property
     def virtual(self):
-        return spack.repo.path.is_virtual(self.name)
+        return spack.repo.PATH.is_virtual(self.name)
 
     @property
     def concrete(self):
@@ -2272,7 +2272,7 @@ def override(init_spec, change_spec):
         # TODO: this doesn't account for the case where the changed spec
         # (and the user spec) have dependencies
         new_spec = init_spec.copy()
-        package_cls = spack.repo.path.get_pkg_class(new_spec.name)
+        package_cls = spack.repo.PATH.get_pkg_class(new_spec.name)
         if change_spec.versions and not change_spec.versions == vn.any_version:
             new_spec.versions = change_spec.versions
         for variant, value in change_spec.variants.items():
@@ -2546,7 +2546,7 @@ def validate_detection(self):
         assert isinstance(self.extra_attributes, collections.abc.Mapping), msg
 
         # Validate the spec calling a package specific method
-        pkg_cls = spack.repo.path.get_pkg_class(self.name)
+        pkg_cls = spack.repo.PATH.get_pkg_class(self.name)
         validate_fn = getattr(pkg_cls, "validate_detected_spec", lambda x, y: None)
         validate_fn(self, self.extra_attributes)
 
@@ -2645,7 +2645,7 @@ def _expand_virtual_packages(self, concretizer):
         """
         # Make an index of stuff this spec already provides
         self_index = spack.provider_index.ProviderIndex(
-            repository=spack.repo.path, specs=self.traverse(), restrict=True
+            repository=spack.repo.PATH, specs=self.traverse(), restrict=True
         )
         changed = False
         done = False
@@ -2785,7 +2785,7 @@ def _old_concretize(self, tests=False, deprecation_warning=True):
         visited_user_specs = set()
         for dep in self.traverse():
             visited_user_specs.add(dep.name)
-            pkg_cls = spack.repo.path.get_pkg_class(dep.name)
+            pkg_cls = spack.repo.PATH.get_pkg_class(dep.name)
             visited_user_specs.update(x.name for x in pkg_cls(dep).provided)
 
         extra = set(user_spec_deps.keys()).difference(visited_user_specs)
@@ -2868,7 +2868,7 @@ def inject_patches_variant(root):
             # we can do it as late as possible to allow as much
             # compatibility across repositories as possible.
             if s.namespace is None:
-                s.namespace = spack.repo.path.repo_for_pkg(s.name).namespace
+                s.namespace = spack.repo.PATH.repo_for_pkg(s.name).namespace
 
             if s.concrete:
                 continue
@@ -2926,7 +2926,7 @@ def ensure_external_path_if_external(external_spec):
 
             # Get the path from the module the package can override the default
             # (this is mostly needed for Cray)
-            pkg_cls = spack.repo.path.get_pkg_class(external_spec.name)
+            pkg_cls = spack.repo.PATH.get_pkg_class(external_spec.name)
             package = pkg_cls(external_spec)
             external_spec.external_path = getattr(
                 package, "external_prefix", md.path_from_modules(external_spec.external_modules)
@@ -2983,9 +2983,12 @@ def _new_concretize(self, tests=False):
             providers = [spec.name for spec in answer.values() if spec.package.provides(name)]
             name = providers[0]
 
-        assert name in answer
+        node = spack.solver.asp.SpecBuilder.make_node(pkg=name)
+        assert (
+            node in answer
+        ), f"cannot find {name} in the list of specs {','.join([n.pkg for n in answer.keys()])}"
 
-        concretized = answer[name]
+        concretized = answer[node]
         self._dup(concretized)
 
     def concretize(self, tests=False):
@@ -3200,7 +3203,7 @@ def _find_provider(self, vdep, provider_index):
         Raise an exception if there is a conflicting virtual
         dependency already in this spec.
         """
-        assert spack.repo.path.is_virtual_safe(vdep.name), vdep
+        assert spack.repo.PATH.is_virtual_safe(vdep.name), vdep
 
         # note that this defensively copies.
         providers = provider_index.providers_for(vdep)
@@ -3266,7 +3269,7 @@ def _merge_dependency(self, dependency, visited, spec_deps, provider_index, test
         # If it's a virtual dependency, try to find an existing
         # provider in the spec, and merge that.
         virtuals = ()
-        if spack.repo.path.is_virtual_safe(dep.name):
+        if spack.repo.PATH.is_virtual_safe(dep.name):
             virtuals = (dep.name,)
             visited.add(dep.name)
             provider = self._find_provider(dep, provider_index)
@@ -3274,11 +3277,11 @@ def _merge_dependency(self, dependency, visited, spec_deps, provider_index, test
                 dep = provider
         else:
             index = spack.provider_index.ProviderIndex(
-                repository=spack.repo.path, specs=[dep], restrict=True
+                repository=spack.repo.PATH, specs=[dep], restrict=True
             )
             items = list(spec_deps.items())
             for name, vspec in items:
-                if not spack.repo.path.is_virtual_safe(vspec.name):
+                if not spack.repo.PATH.is_virtual_safe(vspec.name):
                     continue
 
                 if index.providers_for(vspec):
@@ -3428,7 +3431,7 @@ def normalize(self, force=False, tests=False, user_spec_deps=None):
         # Initialize index of virtual dependency providers if
         # concretize didn't pass us one already
         provider_index = spack.provider_index.ProviderIndex(
-            repository=spack.repo.path, specs=[s for s in all_spec_deps.values()], restrict=True
+            repository=spack.repo.PATH, specs=[s for s in all_spec_deps.values()], restrict=True
         )
 
         # traverse the package DAG and fill out dependencies according
@@ -3459,7 +3462,7 @@ def validate_or_raise(self):
         for spec in self.traverse():
             # raise an UnknownPackageError if the spec's package isn't real.
             if (not spec.virtual) and spec.name:
-                spack.repo.path.get_pkg_class(spec.fullname)
+                spack.repo.PATH.get_pkg_class(spec.fullname)
 
             # validate compiler in addition to the package name.
             if spec.compiler:
@@ -3519,7 +3522,8 @@ def update_variant_validate(self, variant_name, values):
         for value in values:
             if self.variants.get(variant_name):
                 msg = (
-                    "Cannot append a value to a single-valued " "variant with an already set value"
+                    f"cannot append the new value '{value}' to the single-valued "
+                    f"variant '{self.variants[variant_name]}'"
                 )
                 assert pkg_variant.multi, msg
                 self.variants[variant_name].append(value)
@@ -3527,7 +3531,7 @@ def update_variant_validate(self, variant_name, values):
                 variant = pkg_variant.make_variant(value)
                 self.variants[variant_name] = variant
 
-        pkg_cls = spack.repo.path.get_pkg_class(self.name)
+        pkg_cls = spack.repo.PATH.get_pkg_class(self.name)
         pkg_variant.validate_or_raise(self.variants[variant_name], pkg_cls)
 
     def constrain(self, other, deps=True):
@@ -3732,8 +3736,8 @@ def _intersects(self, other: "Spec", deps: bool = True) -> bool:
         if self.name != other.name and self.name and other.name:
             if self.virtual and other.virtual:
                 # Two virtual specs intersect only if there are providers for both
-                lhs = spack.repo.path.providers_for(str(self))
-                rhs = spack.repo.path.providers_for(str(other))
+                lhs = spack.repo.PATH.providers_for(str(self))
+                rhs = spack.repo.PATH.providers_for(str(other))
                 intersection = [s for s in lhs if any(s.intersects(z) for z in rhs)]
                 return bool(intersection)
 
@@ -3742,7 +3746,7 @@ def _intersects(self, other: "Spec", deps: bool = True) -> bool:
                 virtual_spec, non_virtual_spec = (self, other) if self.virtual else (other, self)
                 try:
                     # Here we might get an abstract spec
-                    pkg_cls = spack.repo.path.get_pkg_class(non_virtual_spec.fullname)
+                    pkg_cls = spack.repo.PATH.get_pkg_class(non_virtual_spec.fullname)
                     pkg = pkg_cls(non_virtual_spec)
                 except spack.repo.UnknownEntityError:
                     # If we can't get package info on this spec, don't treat
@@ -3813,10 +3817,10 @@ def _intersects_dependencies(self, other):
 
         # For virtual dependencies, we need to dig a little deeper.
         self_index = spack.provider_index.ProviderIndex(
-            repository=spack.repo.path, specs=self.traverse(), restrict=True
+            repository=spack.repo.PATH, specs=self.traverse(), restrict=True
         )
         other_index = spack.provider_index.ProviderIndex(
-            repository=spack.repo.path, specs=other.traverse(), restrict=True
+            repository=spack.repo.PATH, specs=other.traverse(), restrict=True
         )
 
         # This handles cases where there are already providers for both vpkgs
@@ -3857,7 +3861,7 @@ def _satisfies(self, other: "Spec", deps: bool = True) -> bool:
             if not self.virtual and other.virtual:
                 try:
                     # Here we might get an abstract spec
-                    pkg_cls = spack.repo.path.get_pkg_class(self.fullname)
+                    pkg_cls = spack.repo.PATH.get_pkg_class(self.fullname)
                     pkg = pkg_cls(self)
                 except spack.repo.UnknownEntityError:
                     # If we can't get package info on this spec, don't treat
@@ -3939,8 +3943,8 @@ def patches(self):
             # translate patch sha256sums to patch objects by consulting the index
             if self._patches_assigned():
                 for sha256 in self.variants["patches"]._patches_in_order_of_appearance:
-                    index = spack.repo.path.patch_index
-                    pkg_cls = spack.repo.path.get_pkg_class(self.name)
+                    index = spack.repo.PATH.patch_index
+                    pkg_cls = spack.repo.PATH.get_pkg_class(self.name)
                     patch = index.patch_for_package(sha256, pkg_cls)
                     self._patches.append(patch)
 

lib/spack/spack/stage.py

@@ -326,7 +326,7 @@ def __init__(
         self.keep = keep
 
         # File lock for the stage directory.  We use one file for all
-        # stage locks. See spack.database.Database.prefix_lock for
+        # stage locks. See spack.database.Database.prefix_locker.lock for
         # details on this approach.
         self._lock = None
         if lock:
@@ -484,7 +484,7 @@ def fetch(self, mirror_only=False, err_msg=None):
 
             if self.default_fetcher.cachable:
                 for rel_path in reversed(list(self.mirror_paths)):
-                    cache_fetcher = spack.caches.fetch_cache.fetcher(
+                    cache_fetcher = spack.caches.FETCH_CACHE.fetcher(
                         rel_path, digest, expand=expand, extension=extension
                     )
                     fetchers.insert(0, cache_fetcher)
@@ -577,7 +577,7 @@ def check(self):
             self.fetcher.check()
 
     def cache_local(self):
-        spack.caches.fetch_cache.store(self.fetcher, self.mirror_paths.storage_path)
+        spack.caches.FETCH_CACHE.store(self.fetcher, self.mirror_paths.storage_path)
 
     def cache_mirror(self, mirror, stats):
         """Perform a fetch if the resource is not already cached

lib/spack/spack/store.py

@@ -25,13 +25,14 @@
 from typing import Any, Callable, Dict, Generator, List, Optional, Union
 
 import llnl.util.lang
-import llnl.util.tty as tty
+from llnl.util import tty
 
 import spack.config
 import spack.database
 import spack.directory_layout
 import spack.error
 import spack.paths
+import spack.spec
 import spack.util.path
 
 #: default installation root, relative to the Spack install path
@@ -134,18 +135,21 @@ def parse_install_tree(config_dict):
 class Store:
     """A store is a path full of installed Spack packages.
 
-    Stores consist of packages installed according to a
-    ``DirectoryLayout``, along with an index, or _database_ of their
-    contents.  The directory layout controls what paths look like and how
-    Spack ensures that each unique spec gets its own unique directory (or
-    not, though we don't recommend that). The database is a single file
-    that caches metadata for the entire Spack installation.  It prevents
-    us from having to spider the install tree to figure out what's there.
+    Stores consist of packages installed according to a ``DirectoryLayout``, along with a database
+    of their contents.
+
+    The directory layout controls what paths look like and how Spack ensures that each unique spec
+    gets its own unique directory (or not, though we don't recommend that).
+
+    The database is a single file that caches metadata for the entire Spack installation. It
+    prevents us from having to spider the install tree to figure out what's there.
+
+    The store is also able to lock installation prefixes, and to mark installation failures.
 
     Args:
         root: path to the root of the install tree
-        unpadded_root: path to the root of the install tree without padding.
-            The sbang script has to be installed here to work with padded roots
+        unpadded_root: path to the root of the install tree without padding. The sbang script has
+            to be installed here to work with padded roots
         projections: expression according to guidelines that describes how to construct a path to
             a package prefix in this store
         hash_length: length of the hashes used in the directory layout. Spec hash suffixes will be
@@ -170,6 +174,19 @@ def __init__(
         self.upstreams = upstreams
         self.lock_cfg = lock_cfg
         self.db = spack.database.Database(root, upstream_dbs=upstreams, lock_cfg=lock_cfg)
+
+        timeout_format_str = (
+            f"{str(lock_cfg.package_timeout)}s" if lock_cfg.package_timeout else "No timeout"
+        )
+        tty.debug("PACKAGE LOCK TIMEOUT: {0}".format(str(timeout_format_str)))
+
+        self.prefix_locker = spack.database.SpecLocker(
+            spack.database.prefix_lock_path(root), default_timeout=lock_cfg.package_timeout
+        )
+        self.failure_tracker = spack.database.FailureTracker(
+            self.root, default_timeout=lock_cfg.package_timeout
+        )
+
         self.layout = spack.directory_layout.DirectoryLayout(
             root, projections=projections, hash_length=hash_length
         )
@@ -195,7 +212,7 @@ def create(configuration: ConfigurationType) -> Store:
     Args:
         configuration: configuration to create a store.
     """
-    configuration = configuration or spack.config.config
+    configuration = configuration or spack.config.CONFIG
     config_dict = configuration.get("config")
     root, unpadded_root, projections = parse_install_tree(config_dict)
     hash_length = configuration.get("config:install_hash_length")
@@ -217,7 +234,7 @@ def create(configuration: ConfigurationType) -> Store:
 
 
 def _create_global() -> Store:
-    result = create(configuration=spack.config.config)
+    result = create(configuration=spack.config.CONFIG)
     return result
 
 
@@ -355,10 +372,10 @@ def use_store(
 
     # Swap the store with the one just constructed and return it
     ensure_singleton_created()
-    spack.config.config.push_scope(
+    spack.config.CONFIG.push_scope(
         spack.config.InternalConfigScope(name=scope_name, data={"config": {"install_tree": data}})
     )
-    temporary_store = create(configuration=spack.config.config)
+    temporary_store = create(configuration=spack.config.CONFIG)
     original_store, STORE = STORE, temporary_store
 
     try:
@@ -366,7 +383,7 @@ def use_store(
     finally:
         # Restore the original store
         STORE = original_store
-        spack.config.config.remove_scope(scope_name=scope_name)
+        spack.config.CONFIG.remove_scope(scope_name=scope_name)
 
 
 class MatchError(spack.error.SpackError):

lib/spack/spack/subprocess_context.py

@@ -94,15 +94,15 @@ class TestState:
 
     def __init__(self):
         if _SERIALIZE:
-            self.config = spack.config.config
+            self.config = spack.config.CONFIG
             self.platform = spack.platforms.host
             self.test_patches = store_patches()
             self.store = spack.store.STORE
 
     def restore(self):
         if _SERIALIZE:
-            spack.config.config = self.config
-            spack.repo.path = spack.repo.create(self.config)
+            spack.config.CONFIG = self.config
+            spack.repo.PATH = spack.repo.create(self.config)
             spack.platforms.host = self.platform
             spack.store.STORE = self.store
             self.test_patches.restore()

lib/spack/spack/tag.py

@@ -32,10 +32,10 @@ def packages_with_tags(tags, installed, skip_empty):
     """
     tag_pkgs = collections.defaultdict(lambda: list)
     spec_names = _get_installed_package_names() if installed else []
-    keys = spack.repo.path.tag_index if tags is None else tags
+    keys = spack.repo.PATH.tag_index if tags is None else tags
     for tag in keys:
         packages = [
-            name for name in spack.repo.path.tag_index[tag] if not installed or name in spec_names
+            name for name in spack.repo.PATH.tag_index[tag] if not installed or name in spec_names
         ]
         if packages or not skip_empty:
             tag_pkgs[tag] = packages

lib/spack/spack/test/architecture.py

@@ -199,15 +199,11 @@ def test_satisfy_strict_constraint_when_not_concrete(architecture_tuple, constra
     ],
 )
 @pytest.mark.usefixtures("mock_packages", "config")
+@pytest.mark.only_clingo("Fixing the parser broke this test for the original concretizer.")
 def test_concretize_target_ranges(root_target_range, dep_target_range, result, monkeypatch):
     # Monkeypatch so that all concretization is done as if the machine is core2
     monkeypatch.setattr(spack.platforms.test.Test, "default", "core2")
 
-    # use foobar=bar to make the problem simpler for the old concretizer
-    # the new concretizer should not need that help
-    if spack.config.get("config:concretizer") == "original":
-        pytest.skip("Fixing the parser broke this test for the original concretizer.")
-
     spec_str = "a %%gcc@10 foobar=bar target=%s ^b target=%s" % (
         root_target_range,
         dep_target_range,

lib/spack/spack/test/bindist.py

@@ -37,7 +37,7 @@
 from spack.paths import test_path
 from spack.spec import Spec
 
-pytestmark = pytest.mark.skipif(sys.platform == "win32", reason="does not run on windows")
+pytestmark = pytest.mark.not_on_windows("does not run on windows")
 
 mirror_cmd = spack.main.SpackCommand("mirror")
 install_cmd = spack.main.SpackCommand("install")
@@ -51,7 +51,7 @@
 def cache_directory(tmpdir):
     fetch_cache_dir = tmpdir.ensure("fetch_cache", dir=True)
     fsc = spack.fetch_strategy.FsCache(str(fetch_cache_dir))
-    spack.config.caches, old_cache_path = fsc, spack.caches.fetch_cache
+    spack.config.caches, old_cache_path = fsc, spack.caches.FETCH_CACHE
 
     yield spack.config.caches
 
@@ -115,8 +115,8 @@ def default_config(tmpdir, config_directory, monkeypatch, install_mockery_mutabl
         ]
     )
 
-    spack.config.config, old_config = cfg, spack.config.config
-    spack.config.config.set("repos", [spack.paths.mock_packages_path])
+    spack.config.CONFIG, old_config = cfg, spack.config.CONFIG
+    spack.config.CONFIG.set("repos", [spack.paths.mock_packages_path])
     njobs = spack.config.get("config:build_jobs")
     if not njobs:
         spack.config.set("config:build_jobs", 4, scope="user")
@@ -138,9 +138,9 @@ def default_config(tmpdir, config_directory, monkeypatch, install_mockery_mutabl
     if not timeout:
         spack.config.set("config:connect_timeout", 10, scope="user")
 
-    yield spack.config.config
+    yield spack.config.CONFIG
 
-    spack.config.config = old_config
+    spack.config.CONFIG = old_config
     mutable_dir.remove()
 
 

lib/spack/spack/test/bootstrap.py

@@ -26,11 +26,11 @@ def test_store_is_restored_correctly_after_bootstrap(mutable_config, tmpdir):
     user_path = str(tmpdir.join("store"))
     with spack.store.use_store(user_path):
         assert spack.store.STORE.root == user_path
-        assert spack.config.config.get("config:install_tree:root") == user_path
+        assert spack.config.CONFIG.get("config:install_tree:root") == user_path
         with spack.bootstrap.ensure_bootstrap_configuration():
             assert spack.store.STORE.root == spack.bootstrap.config.store_path()
         assert spack.store.STORE.root == user_path
-        assert spack.config.config.get("config:install_tree:root") == user_path
+        assert spack.config.CONFIG.get("config:install_tree:root") == user_path
 
 
 @pytest.mark.regression("38963")
@@ -40,11 +40,11 @@ def test_store_padding_length_is_zero_during_bootstrapping(mutable_config, tmpdi
     """
     user_path = str(tmpdir.join("store"))
     with spack.store.use_store(user_path, extra_data={"padded_length": 512}):
-        assert spack.config.config.get("config:install_tree:padded_length") == 512
+        assert spack.config.CONFIG.get("config:install_tree:padded_length") == 512
         with spack.bootstrap.ensure_bootstrap_configuration():
             assert spack.store.STORE.root == spack.bootstrap.config.store_path()
-            assert spack.config.config.get("config:install_tree:padded_length") == 0
-        assert spack.config.config.get("config:install_tree:padded_length") == 512
+            assert spack.config.CONFIG.get("config:install_tree:padded_length") == 0
+        assert spack.config.CONFIG.get("config:install_tree:padded_length") == 512
 
 
 @pytest.mark.regression("38963")
@@ -54,15 +54,15 @@ def test_install_tree_customization_is_respected(mutable_config, tmp_path):
     """
     spack.store.reinitialize()
     store_dir = tmp_path / "store"
-    spack.config.config.set("config:install_tree:root", str(store_dir))
+    spack.config.CONFIG.set("config:install_tree:root", str(store_dir))
     with spack.bootstrap.ensure_bootstrap_configuration():
         assert spack.store.STORE.root == spack.bootstrap.config.store_path()
         assert (
-            spack.config.config.get("config:install_tree:root")
+            spack.config.CONFIG.get("config:install_tree:root")
             == spack.bootstrap.config.store_path()
         )
-        assert spack.config.config.get("config:install_tree:padded_length") == 0
-    assert spack.config.config.get("config:install_tree:root") == str(store_dir)
+        assert spack.config.CONFIG.get("config:install_tree:padded_length") == 0
+    assert spack.config.CONFIG.get("config:install_tree:root") == str(store_dir)
     assert spack.store.STORE.root == str(store_dir)
 
 
@@ -185,12 +185,12 @@ def test_bootstrap_custom_store_in_environment(mutable_config, tmpdir):
 
 def test_nested_use_of_context_manager(mutable_config):
     """Test nested use of the context manager"""
-    user_config = spack.config.config
+    user_config = spack.config.CONFIG
     with spack.bootstrap.ensure_bootstrap_configuration():
-        assert spack.config.config != user_config
+        assert spack.config.CONFIG != user_config
         with spack.bootstrap.ensure_bootstrap_configuration():
-            assert spack.config.config != user_config
-    assert spack.config.config == user_config
+            assert spack.config.CONFIG != user_config
+    assert spack.config.CONFIG == user_config
 
 
 @pytest.mark.parametrize("expected_missing", [False, True])

lib/spack/spack/test/build_distribution.py

@@ -5,7 +5,6 @@
 
 import os
 import os.path
-import sys
 
 import pytest
 
@@ -16,7 +15,7 @@
 
 install = spack.main.SpackCommand("install")
 
-pytestmark = pytest.mark.skipif(sys.platform == "win32", reason="does not run on windows")
+pytestmark = pytest.mark.not_on_windows("does not run on windows")
 
 
 def test_build_tarball_overwrite(install_mockery, mock_fetch, monkeypatch, tmpdir):

lib/spack/spack/test/build_environment.py

@@ -6,7 +6,6 @@
 import os
 import platform
 import posixpath
-import sys
 
 import pytest
 
@@ -119,7 +118,7 @@ def __call__(self, *args, **kwargs):
     return mock_module_cmd
 
 
-@pytest.mark.skipif(sys.platform == "win32", reason="Static to Shared not supported on Win (yet)")
+@pytest.mark.not_on_windows("Static to Shared not supported on Win (yet)")
 def test_static_to_shared_library(build_environment):
     os.environ["SPACK_TEST_COMMAND"] = "dump-args"
 

lib/spack/spack/test/build_systems.py

@@ -5,7 +5,6 @@
 
 import glob
 import os
-import sys
 
 import py.path
 import pytest
@@ -23,8 +22,6 @@
 
 DATA_PATH = os.path.join(spack.paths.test_path, "data")
 
-pytestmark = pytest.mark.skipif(sys.platform == "win32", reason="does not run on windows")
-
 
 @pytest.fixture()
 def concretize_and_setup(default_mock_concretization):
@@ -45,6 +42,7 @@ def _func(dir_str):
     return _func
 
 
+@pytest.mark.not_on_windows("make not available on Windows")
 @pytest.mark.usefixtures("config", "mock_packages", "working_env")
 class TestTargets:
     @pytest.mark.parametrize(
@@ -93,6 +91,7 @@ def test_negative_ninja_check(self, input_dir, test_dir, concretize_and_setup):
             s.package._if_ninja_target_execute("check")
 
 
+@pytest.mark.not_on_windows("autotools not available on windows")
 @pytest.mark.usefixtures("config", "mock_packages")
 class TestAutotoolsPackage:
     def test_with_or_without(self, default_mock_concretization):

lib/spack/spack/test/builder.py

@@ -3,7 +3,6 @@
 #
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
 import os.path
-import sys
 
 import pytest
 
@@ -106,10 +105,7 @@ def test_old_style_compatibility_with_super(spec_str, method_name, expected):
     assert value == expected
 
 
-@pytest.mark.skipif(
-    sys.platform == "win32",
-    reason="log_ouput cannot currently be used outside of subprocess on Windows",
-)
+@pytest.mark.not_on_windows("log_ouput cannot currently be used outside of subprocess on Windows")
 @pytest.mark.regression("33928")
 @pytest.mark.usefixtures("builder_test_repository", "config", "working_env")
 @pytest.mark.disable_clean_stage_check
@@ -153,7 +149,7 @@ def test_monkey_patching_test_log_file():
 
 # Windows context manager's __exit__ fails with ValueError ("I/O operation
 # on closed file").
-@pytest.mark.skipif(sys.platform == "win32", reason="Does not run on windows")
+@pytest.mark.not_on_windows("Does not run on windows")
 def test_install_time_test_callback(tmpdir, config, mock_packages, mock_stage):
     """Confirm able to run stand-alone test as a post-install callback."""
     s = spack.spec.Spec("py-test-callback").concretized()

lib/spack/spack/test/buildrequest.py

@@ -15,7 +15,7 @@ def test_build_request_errors(install_mockery):
         inst.BuildRequest("abc", {})
 
     spec = spack.spec.Spec("trivial-install-test-package")
-    pkg_cls = spack.repo.path.get_pkg_class(spec.name)
+    pkg_cls = spack.repo.PATH.get_pkg_class(spec.name)
     with pytest.raises(ValueError, match="must have a concrete spec"):
         inst.BuildRequest(pkg_cls(spec), {})