diff --git a/.github/workflows/audit.yaml b/.github/workflows/audit.yaml
index ca9c02e62d4..3d8e1f10ae9 100644
--- a/.github/workflows/audit.yaml
+++ b/.github/workflows/audit.yaml
@@ -34,6 +34,7 @@ jobs:
       run: |
           . share/spack/setup-env.sh
           coverage run $(which spack) audit packages
+          coverage run $(which spack) audit externals        
           coverage combine
           coverage xml
     - name: Package audits (without coverage)
@@ -41,6 +42,7 @@ jobs:
       run: |
           . share/spack/setup-env.sh
           $(which spack) audit packages
+          $(which spack) audit externals
     - uses: codecov/codecov-action@eaaf4bedf32dbdc6b720b63067d99c4d77d6047d # @v2.1.0
       if: ${{ inputs.with_coverage == 'true' }}
       with:
diff --git a/lib/spack/docs/packaging_guide.rst b/lib/spack/docs/packaging_guide.rst
index f433996ec7d..d25009532ad 100644
--- a/lib/spack/docs/packaging_guide.rst
+++ b/lib/spack/docs/packaging_guide.rst
@@ -6196,7 +6196,100 @@ follows:
                "foo-package@{0}".format(version_str)
            )
 
-.. _package-lifecycle:
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+Add detection tests to packages
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+To ensure that software is detected correctly for multiple configurations
+and on different systems users can write a ``detection_test.yaml`` file and
+put it in the package directory alongside the ``package.py`` file.
+This YAML file contains enough information for Spack to mock an environment
+and try to check if the detection logic yields the results that are expected.
+
+As a general rule, attributes at the top-level of ``detection_test.yaml``
+represent search mechanisms and they each map to a list of tests that should confirm
+the validity of the package's detection logic.
+
+The detection tests can be run with the following command:
+
+.. code-block:: console
+
+   $ spack audit externals
+
+Errors that have been detected are reported to screen.
+
+""""""""""""""""""""""""""
+Tests for PATH inspections
+""""""""""""""""""""""""""
+
+Detection tests insisting on ``PATH`` inspections are listed under
+the ``paths`` attribute:
+
+.. code-block:: yaml
+
+   paths:
+   - layout:
+     - executables:
+       - "bin/clang-3.9"
+       - "bin/clang++-3.9"
+       script: |
+         echo "clang version 3.9.1-19ubuntu1 (tags/RELEASE_391/rc2)"
+         echo "Target: x86_64-pc-linux-gnu"
+         echo "Thread model: posix"
+         echo "InstalledDir: /usr/bin"
+     results:
+     - spec: 'llvm@3.9.1 +clang~lld~lldb'
+
+Each test is performed by first creating a temporary directory structure as
+specified in the corresponding ``layout`` and by then running
+package detection and checking that the outcome matches the expected
+``results``. The exact details on how to specify both the ``layout`` and the
+``results`` are reported in the table below:
+
+.. list-table:: Test based on PATH inspections
+   :header-rows: 1
+
+   * - Option Name
+     - Description
+     - Allowed Values
+     - Required Field
+   * - ``layout``
+     - Specifies the filesystem tree used for the test
+     - List of objects
+     - Yes
+   * - ``layout:[0]:executables``
+     - Relative paths for the mock executables to be created
+     - List of strings
+     - Yes
+   * - ``layout:[0]:script``
+     - Mock logic for the executable
+     - Any valid shell script
+     - Yes
+   * - ``results``
+     - List of expected results
+     - List of objects (empty if no result is expected)
+     - Yes
+   * - ``results:[0]:spec``
+     - A spec that is expected from detection
+     - Any valid spec
+     - Yes
+
+"""""""""""""""""""""""""""""""
+Reuse tests from other packages
+"""""""""""""""""""""""""""""""
+
+When using a custom repository, it is possible to customize a package that already exists in ``builtin``
+and reuse its external tests. To do so, just write a ``detection_tests.yaml`` alongside the customized
+``package.py`` with an ``includes`` attribute. For instance the ``detection_tests.yaml`` for
+``myrepo.llvm`` might look like:
+
+.. code-block:: yaml
+
+   includes:
+   - "builtin.llvm"
+
+This YAML file instructs Spack to run the detection tests defined in ``builtin.llvm`` in addition to
+those locally defined in the file.
 
 -----------------------------
 Style guidelines for packages
diff --git a/lib/spack/spack/audit.py b/lib/spack/spack/audit.py
index c3a028a72b1..176c45487f5 100644
--- a/lib/spack/spack/audit.py
+++ b/lib/spack/spack/audit.py
@@ -38,10 +38,13 @@ def _search_duplicate_compilers(error_cls):
 import ast
 import collections
 import collections.abc
+import glob
 import inspect
 import itertools
+import pathlib
 import pickle
 import re
+import warnings
 from urllib.request import urlopen
 
 import llnl.util.lang
@@ -798,3 +801,76 @@ def _analyze_variants_in_directive(pkg, constraint, directive, error_cls):
             errors.append(err)
 
     return errors
+
+
+#: Sanity checks on package directives
+external_detection = AuditClass(
+    group="externals",
+    tag="PKG-EXTERNALS",
+    description="Sanity checks for external software detection",
+    kwargs=("pkgs",),
+)
+
+
+def packages_with_detection_tests():
+    """Return the list of packages with a corresponding detection_test.yaml file."""
+    import spack.config
+    import spack.util.path
+
+    to_be_tested = []
+    for current_repo in spack.repo.PATH.repos:
+        namespace = current_repo.namespace
+        packages_dir = pathlib.PurePath(current_repo.packages_path)
+        pattern = packages_dir / "**" / "detection_test.yaml"
+        pkgs_with_tests = [
+            f"{namespace}.{str(pathlib.PurePath(x).parent.name)}" for x in glob.glob(str(pattern))
+        ]
+        to_be_tested.extend(pkgs_with_tests)
+
+    return to_be_tested
+
+
+@external_detection
+def _test_detection_by_executable(pkgs, error_cls):
+    """Test drive external detection for packages"""
+    import spack.detection
+
+    errors = []
+
+    # Filter the packages and retain only the ones with detection tests
+    pkgs_with_tests = packages_with_detection_tests()
+    selected_pkgs = []
+    for current_package in pkgs_with_tests:
+        _, unqualified_name = spack.repo.partition_package_name(current_package)
+        # Check for both unqualified name and qualified name
+        if unqualified_name in pkgs or current_package in pkgs:
+            selected_pkgs.append(current_package)
+    selected_pkgs.sort()
+
+    if not selected_pkgs:
+        summary = "No detection test to run"
+        details = [f'  "{p}" has no detection test' for p in pkgs]
+        warnings.warn("\n".join([summary] + details))
+        return errors
+
+    for pkg_name in selected_pkgs:
+        for idx, test_runner in enumerate(
+            spack.detection.detection_tests(pkg_name, spack.repo.PATH)
+        ):
+            specs = test_runner.execute()
+            expected_specs = test_runner.expected_specs
+
+            not_detected = set(expected_specs) - set(specs)
+            if not_detected:
+                summary = pkg_name + ": cannot detect some specs"
+                details = [f'"{s}" was not detected [test_id={idx}]' for s in sorted(not_detected)]
+                errors.append(error_cls(summary=summary, details=details))
+
+            not_expected = set(specs) - set(expected_specs)
+            if not_expected:
+                summary = pkg_name + ": detected unexpected specs"
+                msg = '"{0}" was detected, but was not expected [test_id={1}]'
+                details = [msg.format(s, idx) for s in sorted(not_expected)]
+                errors.append(error_cls(summary=summary, details=details))
+
+    return errors
diff --git a/lib/spack/spack/cmd/audit.py b/lib/spack/spack/cmd/audit.py
index cd56dfadd95..86eea9f7bc8 100644
--- a/lib/spack/spack/cmd/audit.py
+++ b/lib/spack/spack/cmd/audit.py
@@ -3,6 +3,7 @@
 #
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
 import llnl.util.tty as tty
+import llnl.util.tty.colify
 import llnl.util.tty.color as cl
 
 import spack.audit
@@ -20,6 +21,15 @@ def setup_parser(subparser):
     # Audit configuration files
     sp.add_parser("configs", help="audit configuration files")
 
+    # Audit package recipes
+    external_parser = sp.add_parser("externals", help="check external detection in packages")
+    external_parser.add_argument(
+        "--list",
+        action="store_true",
+        dest="list_externals",
+        help="if passed, list which packages have detection tests",
+    )
+
     # Https and other linting
     https_parser = sp.add_parser("packages-https", help="check https in packages")
     https_parser.add_argument(
@@ -29,7 +39,7 @@ def setup_parser(subparser):
     # Audit package recipes
     pkg_parser = sp.add_parser("packages", help="audit package recipes")
 
-    for group in [pkg_parser, https_parser]:
+    for group in [pkg_parser, https_parser, external_parser]:
         group.add_argument(
             "name",
             metavar="PKG",
@@ -62,6 +72,18 @@ def packages_https(parser, args):
     _process_reports(reports)
 
 
+def externals(parser, args):
+    if args.list_externals:
+        msg = "@*{The following packages have detection tests:}"
+        tty.msg(cl.colorize(msg))
+        llnl.util.tty.colify.colify(spack.audit.packages_with_detection_tests(), indent=2)
+        return
+
+    pkgs = args.name or spack.repo.PATH.all_package_names()
+    reports = spack.audit.run_group(args.subcommand, pkgs=pkgs)
+    _process_reports(reports)
+
+
 def list(parser, args):
     for subcommand, check_tags in spack.audit.GROUPS.items():
         print(cl.colorize("@*b{" + subcommand + "}:"))
@@ -78,6 +100,7 @@ def list(parser, args):
 def audit(parser, args):
     subcommands = {
         "configs": configs,
+        "externals": externals,
         "packages": packages,
         "packages-https": packages_https,
         "list": list,
diff --git a/lib/spack/spack/cmd/external.py b/lib/spack/spack/cmd/external.py
index bf29787db9b..081ec803943 100644
--- a/lib/spack/spack/cmd/external.py
+++ b/lib/spack/spack/cmd/external.py
@@ -5,6 +5,7 @@
 import argparse
 import errno
 import os
+import re
 import sys
 from typing import List, Optional
 
@@ -156,11 +157,20 @@ def packages_to_search_for(
 ):
     result = []
     for current_tag in tags:
-        result.extend(spack.repo.PATH.packages_with_tags(current_tag))
+        result.extend(spack.repo.PATH.packages_with_tags(current_tag, full=True))
+
     if names:
-        result = [x for x in result if x in names]
+        # Match both fully qualified and unqualified
+        parts = [rf"(^{x}$|[.]{x}$)" for x in names]
+        select_re = re.compile("|".join(parts))
+        result = [x for x in result if select_re.search(x)]
+
     if exclude:
-        result = [x for x in result if x not in exclude]
+        # Match both fully qualified and unqualified
+        parts = [rf"(^{x}$|[.]{x}$)" for x in exclude]
+        select_re = re.compile("|".join(parts))
+        result = [x for x in result if not select_re.search(x)]
+
     return result
 
 
diff --git a/lib/spack/spack/compilers/aocc.py b/lib/spack/spack/compilers/aocc.py
index 51f7b02e2bd..a642960b7df 100644
--- a/lib/spack/spack/compilers/aocc.py
+++ b/lib/spack/spack/compilers/aocc.py
@@ -112,6 +112,7 @@ def extract_version_from_output(cls, output):
         match = re.search(r"AOCC_(\d+)[._](\d+)[._](\d+)", output)
         if match:
             return ".".join(match.groups())
+        return "unknown"
 
     @classmethod
     def fc_version(cls, fortran_compiler):
diff --git a/lib/spack/spack/cray_manifest.py b/lib/spack/spack/cray_manifest.py
index ac40191d0f5..48ec52d782d 100644
--- a/lib/spack/spack/cray_manifest.py
+++ b/lib/spack/spack/cray_manifest.py
@@ -4,6 +4,9 @@
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
 
 import json
+import os
+import traceback
+import warnings
 
 import jsonschema
 import jsonschema.exceptions
@@ -46,9 +49,29 @@ def translated_compiler_name(manifest_compiler_name):
         )
 
 
-def compiler_from_entry(entry):
+def compiler_from_entry(entry: dict, manifest_path: str):
+    # Note that manifest_path is only passed here to compose a
+    # useful warning message when paths appear to be missing.
     compiler_name = translated_compiler_name(entry["name"])
-    paths = entry["executables"]
+
+    if "prefix" in entry:
+        prefix = entry["prefix"]
+        paths = dict(
+            (lang, os.path.join(prefix, relpath))
+            for (lang, relpath) in entry["executables"].items()
+        )
+    else:
+        paths = entry["executables"]
+
+    # Do a check for missing paths. Note that this isn't possible for
+    # all compiler entries, since their "paths" might actually be
+    # exe names like "cc" that depend on modules being loaded. Cray
+    # manifest entries are always paths though.
+    missing_paths = []
+    for path in paths.values():
+        if not os.path.exists(path):
+            missing_paths.append(path)
+
     # to instantiate a compiler class we may need a concrete version:
     version = "={}".format(entry["version"])
     arch = entry["arch"]
@@ -57,8 +80,18 @@ def compiler_from_entry(entry):
 
     compiler_cls = spack.compilers.class_for_compiler_name(compiler_name)
     spec = spack.spec.CompilerSpec(compiler_cls.name, version)
-    paths = [paths.get(x, None) for x in ("cc", "cxx", "f77", "fc")]
-    return compiler_cls(spec, operating_system, target, paths)
+    path_list = [paths.get(x, None) for x in ("cc", "cxx", "f77", "fc")]
+
+    if missing_paths:
+        warnings.warn(
+            "Manifest entry refers to nonexistent paths:\n\t"
+            + "\n\t".join(missing_paths)
+            + f"\nfor {str(spec)}"
+            + f"\nin {manifest_path}"
+            + "\nPlease report this issue"
+        )
+
+    return compiler_cls(spec, operating_system, target, path_list)
 
 
 def spec_from_entry(entry):
@@ -187,12 +220,21 @@ def read(path, apply_updates):
     tty.debug("{0}: {1} specs read from manifest".format(path, str(len(specs))))
     compilers = list()
     if "compilers" in json_data:
-        compilers.extend(compiler_from_entry(x) for x in json_data["compilers"])
+        compilers.extend(compiler_from_entry(x, path) for x in json_data["compilers"])
     tty.debug("{0}: {1} compilers read from manifest".format(path, str(len(compilers))))
     # Filter out the compilers that already appear in the configuration
     compilers = spack.compilers.select_new_compilers(compilers)
     if apply_updates and compilers:
-        spack.compilers.add_compilers_to_config(compilers, init_config=False)
+        for compiler in compilers:
+            try:
+                spack.compilers.add_compilers_to_config([compiler], init_config=False)
+            except Exception:
+                warnings.warn(
+                    f"Could not add compiler {str(compiler.spec)}: "
+                    f"\n\tfrom manifest: {path}"
+                    "\nPlease reexecute with 'spack -d' and include the stack trace"
+                )
+                tty.debug(f"Include this\n{traceback.format_exc()}")
     if apply_updates:
         for spec in specs.values():
             spack.store.STORE.db.add(spec, directory_layout=None)
diff --git a/lib/spack/spack/detection/__init__.py b/lib/spack/spack/detection/__init__.py
index 73ae34ce639..7c54fb9d49b 100644
--- a/lib/spack/spack/detection/__init__.py
+++ b/lib/spack/spack/detection/__init__.py
@@ -4,6 +4,7 @@
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
 from .common import DetectedPackage, executable_prefix, update_configuration
 from .path import by_path, executables_in_path
+from .test import detection_tests
 
 __all__ = [
     "DetectedPackage",
@@ -11,4 +12,5 @@
     "executables_in_path",
     "executable_prefix",
     "update_configuration",
+    "detection_tests",
 ]
diff --git a/lib/spack/spack/detection/common.py b/lib/spack/spack/detection/common.py
index 50a3a2695a8..0e873c3f555 100644
--- a/lib/spack/spack/detection/common.py
+++ b/lib/spack/spack/detection/common.py
@@ -299,36 +299,36 @@ def find_windows_compiler_bundled_packages() -> List[str]:
 
 
 class WindowsKitExternalPaths:
-    plat_major_ver = None
-    if sys.platform == "win32":
-        plat_major_ver = str(winOs.windows_version()[0])
-
     @staticmethod
-    def find_windows_kit_roots() -> Optional[str]:
+    def find_windows_kit_roots() -> List[str]:
         """Return Windows kit root, typically %programfiles%\\Windows Kits\\10|11\\"""
         if sys.platform != "win32":
-            return None
+            return []
         program_files = os.environ["PROGRAMFILES(x86)"]
-        kit_base = os.path.join(
-            program_files, "Windows Kits", WindowsKitExternalPaths.plat_major_ver
-        )
-        return kit_base
+        kit_base = os.path.join(program_files, "Windows Kits", "**")
+        return glob.glob(kit_base)
 
     @staticmethod
     def find_windows_kit_bin_paths(kit_base: Optional[str] = None) -> List[str]:
         """Returns Windows kit bin directory per version"""
         kit_base = WindowsKitExternalPaths.find_windows_kit_roots() if not kit_base else kit_base
-        assert kit_base is not None, "unexpected value for kit_base"
-        kit_bin = os.path.join(kit_base, "bin")
-        return glob.glob(os.path.join(kit_bin, "[0-9]*", "*\\"))
+        assert kit_base, "Unexpectedly empty value for Windows kit base path"
+        kit_paths = []
+        for kit in kit_base:
+            kit_bin = os.path.join(kit, "bin")
+            kit_paths.extend(glob.glob(os.path.join(kit_bin, "[0-9]*", "*\\")))
+        return kit_paths
 
     @staticmethod
     def find_windows_kit_lib_paths(kit_base: Optional[str] = None) -> List[str]:
         """Returns Windows kit lib directory per version"""
         kit_base = WindowsKitExternalPaths.find_windows_kit_roots() if not kit_base else kit_base
-        assert kit_base is not None, "unexpected value for kit_base"
-        kit_lib = os.path.join(kit_base, "Lib")
-        return glob.glob(os.path.join(kit_lib, "[0-9]*", "*", "*\\"))
+        assert kit_base, "Unexpectedly empty value for Windows kit base path"
+        kit_paths = []
+        for kit in kit_base:
+            kit_lib = os.path.join(kit, "Lib")
+            kit_paths.extend(glob.glob(os.path.join(kit_lib, "[0-9]*", "*", "*\\")))
+        return kit_paths
 
     @staticmethod
     def find_windows_driver_development_kit_paths() -> List[str]:
@@ -347,23 +347,30 @@ def find_windows_kit_reg_installed_roots_paths() -> List[str]:
         if not reg:
             # couldn't find key, return empty list
             return []
-        return WindowsKitExternalPaths.find_windows_kit_lib_paths(
-            reg.get_value("KitsRoot%s" % WindowsKitExternalPaths.plat_major_ver).value
-        )
+        kit_root_reg = re.compile(r"KitsRoot[0-9]+")
+        root_paths = []
+        for kit_root in filter(kit_root_reg.match, reg.get_values().keys()):
+            root_paths.extend(
+                WindowsKitExternalPaths.find_windows_kit_lib_paths(reg.get_value(kit_root).value)
+            )
+        return root_paths
 
     @staticmethod
     def find_windows_kit_reg_sdk_paths() -> List[str]:
-        reg = spack.util.windows_registry.WindowsRegistryView(
-            "SOFTWARE\\WOW6432Node\\Microsoft\\Microsoft SDKs\\Windows\\v%s.0"
-            % WindowsKitExternalPaths.plat_major_ver,
+        sdk_paths = []
+        sdk_regex = re.compile(r"v[0-9]+.[0-9]+")
+        windows_reg = spack.util.windows_registry.WindowsRegistryView(
+            "SOFTWARE\\WOW6432Node\\Microsoft\\Microsoft SDKs\\Windows",
             root_key=spack.util.windows_registry.HKEY.HKEY_LOCAL_MACHINE,
         )
-        if not reg:
-            # couldn't find key, return empty list
-            return []
-        return WindowsKitExternalPaths.find_windows_kit_lib_paths(
-            reg.get_value("InstallationFolder").value
-        )
+        for key in filter(sdk_regex.match, [x.name for x in windows_reg.get_subkeys()]):
+            reg = windows_reg.get_subkey(key)
+            sdk_paths.extend(
+                WindowsKitExternalPaths.find_windows_kit_lib_paths(
+                    reg.get_value("InstallationFolder").value
+                )
+            )
+        return sdk_paths
 
 
 def find_win32_additional_install_paths() -> List[str]:
diff --git a/lib/spack/spack/detection/path.py b/lib/spack/spack/detection/path.py
index 4a085aacd06..4de703ac97b 100644
--- a/lib/spack/spack/detection/path.py
+++ b/lib/spack/spack/detection/path.py
@@ -2,7 +2,7 @@
 # Spack Project Developers. See the top-level COPYRIGHT file for details.
 #
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
-"""Detection of software installed in the system based on paths inspections
+"""Detection of software installed in the system, based on paths inspections
 and running executables.
 """
 import collections
@@ -322,12 +322,14 @@ def by_path(
     path_hints: Optional[List[str]] = None,
     max_workers: Optional[int] = None,
 ) -> Dict[str, List[DetectedPackage]]:
-    """Return the list of packages that have been detected on the system,
-    searching by path.
+    """Return the list of packages that have been detected on the system, keyed by
+    unqualified package name.
 
     Args:
-        packages_to_search: list of package classes to be detected
+        packages_to_search: list of packages to be detected. Each package can be either unqualified
+            of fully qualified
         path_hints: initial list of paths to be searched
+        max_workers: maximum number of workers to search for packages in parallel
     """
     # TODO: Packages should be able to define both .libraries and .executables in the future
     # TODO: determine_spec_details should get all relevant libraries and executables in one call
@@ -355,7 +357,8 @@ def by_path(
                 try:
                     detected = future.result(timeout=DETECTION_TIMEOUT)
                     if detected:
-                        result[pkg_name].extend(detected)
+                        _, unqualified_name = spack.repo.partition_package_name(pkg_name)
+                        result[unqualified_name].extend(detected)
                 except Exception:
                     llnl.util.tty.debug(
                         f"[EXTERNAL DETECTION] Skipping {pkg_name}: timeout reached"
diff --git a/lib/spack/spack/detection/test.py b/lib/spack/spack/detection/test.py
new file mode 100644
index 00000000000..f33040f2929
--- /dev/null
+++ b/lib/spack/spack/detection/test.py
@@ -0,0 +1,187 @@
+# 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)
+"""Create and run mock e2e tests for package detection."""
+import collections
+import contextlib
+import pathlib
+import tempfile
+from typing import Any, Deque, Dict, Generator, List, NamedTuple, Tuple
+
+import jinja2
+
+from llnl.util import filesystem
+
+import spack.repo
+import spack.spec
+from spack.util import spack_yaml
+
+from .path import by_path
+
+
+class MockExecutables(NamedTuple):
+    """Mock executables to be used in detection tests"""
+
+    #: Relative paths for mock executables to be created
+    executables: List[str]
+    #: Shell script for the mock executable
+    script: str
+
+
+class ExpectedTestResult(NamedTuple):
+    """Data structure to model assertions on detection tests"""
+
+    #: Spec to be detected
+    spec: str
+
+
+class DetectionTest(NamedTuple):
+    """Data structure to construct detection tests by PATH inspection.
+
+    Packages may have a YAML file containing the description of one or more detection tests
+    to be performed. Each test creates a few mock executable scripts in a temporary folder,
+    and checks that detection by PATH gives the expected results.
+    """
+
+    pkg_name: str
+    layout: List[MockExecutables]
+    results: List[ExpectedTestResult]
+
+
+class Runner:
+    """Runs an external detection test"""
+
+    def __init__(self, *, test: DetectionTest, repository: spack.repo.RepoPath) -> None:
+        self.test = test
+        self.repository = repository
+        self.tmpdir = tempfile.TemporaryDirectory()
+
+    def execute(self) -> List[spack.spec.Spec]:
+        """Executes a test and returns the specs that have been detected.
+
+        This function sets-up a test in a temporary directory, according to the prescriptions
+        in the test layout, then performs a detection by executables and returns the specs that
+        have been detected.
+        """
+        with self._mock_layout() as path_hints:
+            entries = by_path([self.test.pkg_name], path_hints=path_hints)
+            _, unqualified_name = spack.repo.partition_package_name(self.test.pkg_name)
+            specs = set(x.spec for x in entries[unqualified_name])
+        return list(specs)
+
+    @contextlib.contextmanager
+    def _mock_layout(self) -> Generator[List[str], None, None]:
+        hints = set()
+        try:
+            for entry in self.test.layout:
+                exes = self._create_executable_scripts(entry)
+
+                for mock_executable in exes:
+                    hints.add(str(mock_executable.parent))
+
+            yield list(hints)
+        finally:
+            self.tmpdir.cleanup()
+
+    def _create_executable_scripts(self, mock_executables: MockExecutables) -> List[pathlib.Path]:
+        relative_paths = mock_executables.executables
+        script = mock_executables.script
+        script_template = jinja2.Template("#!/bin/bash\n{{ script }}\n")
+        result = []
+        for mock_exe_path in relative_paths:
+            rel_path = pathlib.Path(mock_exe_path)
+            abs_path = pathlib.Path(self.tmpdir.name) / rel_path
+            abs_path.parent.mkdir(parents=True, exist_ok=True)
+            abs_path.write_text(script_template.render(script=script))
+            filesystem.set_executable(abs_path)
+            result.append(abs_path)
+        return result
+
+    @property
+    def expected_specs(self) -> List[spack.spec.Spec]:
+        return [spack.spec.Spec(r.spec) for r in self.test.results]
+
+
+def detection_tests(pkg_name: str, repository: spack.repo.RepoPath) -> List[Runner]:
+    """Returns a list of test runners for a given package.
+
+    Currently, detection tests are specified in a YAML file, called ``detection_test.yaml``,
+    alongside the ``package.py`` file.
+
+    This function reads that file to create a bunch of ``Runner`` objects.
+
+    Args:
+        pkg_name: name of the package to test
+        repository: repository where the package lives
+    """
+    result = []
+    detection_tests_content = read_detection_tests(pkg_name, repository)
+
+    tests_by_path = detection_tests_content.get("paths", [])
+    for single_test_data in tests_by_path:
+        mock_executables = []
+        for layout in single_test_data["layout"]:
+            mock_executables.append(
+                MockExecutables(executables=layout["executables"], script=layout["script"])
+            )
+        expected_results = []
+        for assertion in single_test_data["results"]:
+            expected_results.append(ExpectedTestResult(spec=assertion["spec"]))
+
+        current_test = DetectionTest(
+            pkg_name=pkg_name, layout=mock_executables, results=expected_results
+        )
+        result.append(Runner(test=current_test, repository=repository))
+
+    return result
+
+
+def read_detection_tests(pkg_name: str, repository: spack.repo.RepoPath) -> Dict[str, Any]:
+    """Returns the normalized content of the detection_tests.yaml associated with the package
+    passed in input.
+
+    The content is merged with that of any package that is transitively included using the
+    "includes" attribute.
+
+    Args:
+        pkg_name: name of the package to test
+        repository: repository in which to search for packages
+    """
+    content_stack, seen = [], set()
+    included_packages: Deque[str] = collections.deque()
+
+    root_detection_yaml, result = _detection_tests_yaml(pkg_name, repository)
+    included_packages.extend(result.get("includes", []))
+    seen |= set(result.get("includes", []))
+
+    while included_packages:
+        current_package = included_packages.popleft()
+        try:
+            current_detection_yaml, content = _detection_tests_yaml(current_package, repository)
+        except FileNotFoundError as e:
+            msg = (
+                f"cannot read the detection tests from the '{current_package}' package, "
+                f"included by {root_detection_yaml}"
+            )
+            raise FileNotFoundError(msg + f"\n\n\t{e}\n")
+
+        content_stack.append((current_package, content))
+        included_packages.extend(x for x in content.get("includes", []) if x not in seen)
+        seen |= set(content.get("includes", []))
+
+    result.setdefault("paths", [])
+    for pkg_name, content in content_stack:
+        result["paths"].extend(content.get("paths", []))
+
+    return result
+
+
+def _detection_tests_yaml(
+    pkg_name: str, repository: spack.repo.RepoPath
+) -> Tuple[pathlib.Path, Dict[str, Any]]:
+    pkg_dir = pathlib.Path(repository.filename_for_package_name(pkg_name)).parent
+    detection_tests_yaml = pkg_dir / "detection_test.yaml"
+    with open(str(detection_tests_yaml)) as f:
+        content = spack_yaml.load(f)
+    return detection_tests_yaml, content
diff --git a/lib/spack/spack/fetch_strategy.py b/lib/spack/spack/fetch_strategy.py
index 8578b110fce..aa96bbbe510 100644
--- a/lib/spack/spack/fetch_strategy.py
+++ b/lib/spack/spack/fetch_strategy.py
@@ -734,7 +734,11 @@ def version_from_git(git_exe):
     @property
     def git(self):
         if not self._git:
-            self._git = spack.util.git.git()
+            try:
+                self._git = spack.util.git.git(required=True)
+            except CommandNotFoundError as exc:
+                tty.error(str(exc))
+                raise
 
             # Disable advice for a quieter fetch
             # https://github.com/git/git/blob/master/Documentation/RelNotes/1.7.2.txt
diff --git a/lib/spack/spack/installer.py b/lib/spack/spack/installer.py
index 95fbae5847d..99ab7d45bd4 100644
--- a/lib/spack/spack/installer.py
+++ b/lib/spack/spack/installer.py
@@ -847,10 +847,11 @@ def get_depflags(self, pkg: "spack.package_base.PackageBase") -> int:
         else:
             cache_only = self.install_args.get("dependencies_cache_only")
 
-        # Include build dependencies if pkg is not installed and cache_only
-        # is False, or if build depdencies are explicitly called for
-        # by include_build_deps.
-        if include_build_deps or not (cache_only or pkg.spec.installed):
+        # Include build dependencies if pkg is going to be built from sources, or
+        # if build deps are explicitly requested.
+        if include_build_deps or not (
+            cache_only or pkg.spec.installed and not pkg.spec.dag_hash() in self.overwrite
+        ):
             depflag |= dt.BUILD
         if self.run_tests(pkg):
             depflag |= dt.TEST
diff --git a/lib/spack/spack/repo.py b/lib/spack/spack/repo.py
index 4391d9a9a23..a89b5dd407d 100644
--- a/lib/spack/spack/repo.py
+++ b/lib/spack/spack/repo.py
@@ -24,7 +24,7 @@
 import traceback
 import types
 import uuid
-from typing import Any, Dict, List, Union
+from typing import Any, Dict, List, Tuple, Union
 
 import llnl.path
 import llnl.util.filesystem as fs
@@ -745,10 +745,18 @@ def all_package_paths(self):
         for name in self.all_package_names():
             yield self.package_path(name)
 
-    def packages_with_tags(self, *tags):
+    def packages_with_tags(self, *tags, full=False):
+        """Returns a list of packages matching any of the tags in input.
+
+        Args:
+            full: if True the package names in the output are fully-qualified
+        """
         r = set()
         for repo in self.repos:
-            r |= set(repo.packages_with_tags(*tags))
+            current = repo.packages_with_tags(*tags)
+            if full:
+                current = [f"{repo.namespace}.{x}" for x in current]
+            r |= set(current)
         return sorted(r)
 
     def all_package_classes(self):
@@ -1124,7 +1132,8 @@ def extensions_for(self, extendee_spec):
     def dirname_for_package_name(self, pkg_name):
         """Get the directory name for a particular package.  This is the
         directory that contains its package.py file."""
-        return os.path.join(self.packages_path, pkg_name)
+        _, unqualified_name = self.partition_package_name(pkg_name)
+        return os.path.join(self.packages_path, unqualified_name)
 
     def filename_for_package_name(self, pkg_name):
         """Get the filename for the module we should load for a particular
@@ -1222,15 +1231,10 @@ def get_pkg_class(self, pkg_name):
         package. Then extracts the package class from the module
         according to Spack's naming convention.
         """
-        namespace, _, pkg_name = pkg_name.rpartition(".")
-        if namespace and (namespace != self.namespace):
-            raise InvalidNamespaceError(
-                "Invalid namespace for %s repo: %s" % (self.namespace, namespace)
-            )
-
+        namespace, pkg_name = self.partition_package_name(pkg_name)
         class_name = nm.mod_to_class(pkg_name)
+        fullname = f"{self.full_namespace}.{pkg_name}"
 
-        fullname = "{0}.{1}".format(self.full_namespace, pkg_name)
         try:
             module = importlib.import_module(fullname)
         except ImportError:
@@ -1241,7 +1245,7 @@ def get_pkg_class(self, pkg_name):
 
         cls = getattr(module, class_name)
         if not inspect.isclass(cls):
-            tty.die("%s.%s is not a class" % (pkg_name, class_name))
+            tty.die(f"{pkg_name}.{class_name} is not a class")
 
         new_cfg_settings = (
             spack.config.get("packages").get(pkg_name, {}).get("package_attributes", {})
@@ -1280,6 +1284,15 @@ def get_pkg_class(self, pkg_name):
 
         return cls
 
+    def partition_package_name(self, pkg_name: str) -> Tuple[str, str]:
+        namespace, pkg_name = partition_package_name(pkg_name)
+        if namespace and (namespace != self.namespace):
+            raise InvalidNamespaceError(
+                f"Invalid namespace for the '{self.namespace}' repo: {namespace}"
+            )
+
+        return namespace, pkg_name
+
     def __str__(self):
         return "[Repo '%s' at '%s']" % (self.namespace, self.root)
 
@@ -1293,6 +1306,20 @@ def __contains__(self, pkg_name):
 RepoType = Union[Repo, RepoPath]
 
 
+def partition_package_name(pkg_name: str) -> Tuple[str, str]:
+    """Given a package name that might be fully-qualified, returns the namespace part,
+    if present and the unqualified package name.
+
+    If the package name is unqualified, the namespace is an empty string.
+
+    Args:
+        pkg_name: a package name, either unqualified like "llvl", or
+            fully-qualified, like "builtin.llvm"
+    """
+    namespace, _, pkg_name = pkg_name.rpartition(".")
+    return namespace, pkg_name
+
+
 def create_repo(root, namespace=None, subdir=packages_dir_name):
     """Create a new repository in root with the specified namespace.
 
diff --git a/lib/spack/spack/test/cmd/external.py b/lib/spack/spack/test/cmd/external.py
index 7d54057b46e..e94d6efe5c4 100644
--- a/lib/spack/spack/test/cmd/external.py
+++ b/lib/spack/spack/test/cmd/external.py
@@ -120,8 +120,9 @@ def test_find_external_cmd_not_buildable(mutable_config, working_env, mock_execu
     "names,tags,exclude,expected",
     [
         # find --all
-        (None, ["detectable"], [], ["find-externals1"]),
+        (None, ["detectable"], [], ["builtin.mock.find-externals1"]),
         # find --all --exclude find-externals1
+        (None, ["detectable"], ["builtin.mock.find-externals1"], []),
         (None, ["detectable"], ["find-externals1"], []),
         # find cmake (and cmake is not detectable)
         (["cmake"], ["detectable"], [], []),
@@ -202,19 +203,6 @@ def fail():
     assert "Skipping manifest and continuing" in output
 
 
-def test_find_external_nonempty_default_manifest_dir(
-    mutable_database, mutable_mock_repo, tmpdir, monkeypatch, directory_with_manifest
-):
-    """The user runs 'spack external find'; the default manifest directory
-    contains a manifest file. Ensure that the specs are read.
-    """
-    monkeypatch.setenv("PATH", "")
-    monkeypatch.setattr(spack.cray_manifest, "default_path", str(directory_with_manifest))
-    external("find")
-    specs = spack.store.STORE.db.query("hwloc")
-    assert any(x.dag_hash() == "hwlocfakehashaaa" for x in specs)
-
-
 def test_find_external_merge(mutable_config, mutable_mock_repo):
     """Check that 'spack find external' doesn't overwrite an existing spec
     entry in packages.yaml.
diff --git a/lib/spack/spack/test/conftest.py b/lib/spack/spack/test/conftest.py
index 25417de6f42..c4b3df92edf 100644
--- a/lib/spack/spack/test/conftest.py
+++ b/lib/spack/spack/test/conftest.py
@@ -1714,17 +1714,6 @@ def brand_new_binary_cache():
     )
 
 
-@pytest.fixture
-def directory_with_manifest(tmpdir):
-    """Create a manifest file in a directory. Used by 'spack external'."""
-    with tmpdir.as_cwd():
-        test_db_fname = "external-db.json"
-        with open(test_db_fname, "w") as db_file:
-            json.dump(spack.test.cray_manifest.create_manifest_content(), db_file)
-
-    yield str(tmpdir)
-
-
 @pytest.fixture()
 def noncyclical_dir_structure(tmpdir):
     """
diff --git a/lib/spack/spack/test/cray_manifest.py b/lib/spack/spack/test/cray_manifest.py
index f9e7ae8594b..123e2ac3f12 100644
--- a/lib/spack/spack/test/cray_manifest.py
+++ b/lib/spack/spack/test/cray_manifest.py
@@ -23,53 +23,6 @@
 import spack.store
 from spack.cray_manifest import compiler_from_entry, entries_to_specs
 
-example_x_json_str = """\
-{
-  "name": "packagex",
-  "hash": "hash-of-x",
-  "prefix": "/path/to/packagex-install/",
-  "version": "1.0",
-  "arch": {
-    "platform": "linux",
-    "platform_os": "centos8",
-    "target": {
-      "name": "haswell"
-    }
-  },
-  "compiler": {
-    "name": "gcc",
-    "version": "10.2.0.cray"
-  },
-  "dependencies": {
-    "packagey": {
-      "hash": "hash-of-y",
-      "type": ["link"]
-    }
-  },
-  "parameters": {
-    "precision": ["double", "float"]
-  }
-}
-"""
-
-
-example_compiler_entry = """\
-{
-  "name": "gcc",
-  "prefix": "/path/to/compiler/",
-  "version": "7.5.0",
-  "arch": {
-    "os": "centos8",
-    "target": "x86_64"
-  },
-  "executables": {
-    "cc": "/path/to/compiler/cc",
-    "cxx": "/path/to/compiler/cxx",
-    "fc": "/path/to/compiler/fc"
-  }
-}
-"""
-
 
 class JsonSpecEntry:
     def __init__(self, name, hash, prefix, version, arch, compiler, dependencies, parameters):
@@ -104,16 +57,19 @@ def __init__(self, platform, os, target):
         self.os = os
         self.target = target
 
-    def to_dict(self):
+    def spec_json(self):
         return {"platform": self.platform, "platform_os": self.os, "target": {"name": self.target}}
 
+    def compiler_json(self):
+        return {"os": self.os, "target": self.target}
+
 
 class JsonCompilerEntry:
     def __init__(self, name, version, arch=None, executables=None):
         self.name = name
         self.version = version
         if not arch:
-            arch = {"os": "centos8", "target": "x86_64"}
+            arch = JsonArchEntry("anyplatform", "anyos", "anytarget")
         if not executables:
             executables = {
                 "cc": "/path/to/compiler/cc",
@@ -127,7 +83,7 @@ def compiler_json(self):
         return {
             "name": self.name,
             "version": self.version,
-            "arch": self.arch,
+            "arch": self.arch.compiler_json(),
             "executables": self.executables,
         }
 
@@ -138,22 +94,58 @@ def spec_json(self):
         return {"name": self.name, "version": self.version}
 
 
-_common_arch = JsonArchEntry(platform="linux", os="centos8", target="haswell").to_dict()
-
-# Intended to match example_compiler_entry above
-_common_compiler = JsonCompilerEntry(
-    name="gcc",
-    version="10.2.0.cray",
-    arch={"os": "centos8", "target": "x86_64"},
-    executables={
-        "cc": "/path/to/compiler/cc",
-        "cxx": "/path/to/compiler/cxx",
-        "fc": "/path/to/compiler/fc",
-    },
-)
+@pytest.fixture
+def _common_arch(test_platform):
+    return JsonArchEntry(
+        platform=test_platform.name,
+        os=test_platform.front_os,
+        target=test_platform.target("fe").name,
+    )
 
 
-def test_compatibility():
+@pytest.fixture
+def _common_compiler(_common_arch):
+    return JsonCompilerEntry(
+        name="gcc",
+        version="10.2.0.2112",
+        arch=_common_arch,
+        executables={
+            "cc": "/path/to/compiler/cc",
+            "cxx": "/path/to/compiler/cxx",
+            "fc": "/path/to/compiler/fc",
+        },
+    )
+
+
+@pytest.fixture
+def _other_compiler(_common_arch):
+    return JsonCompilerEntry(
+        name="clang",
+        version="3.0.0",
+        arch=_common_arch,
+        executables={
+            "cc": "/path/to/compiler/clang",
+            "cxx": "/path/to/compiler/clang++",
+            "fc": "/path/to/compiler/flang",
+        },
+    )
+
+
+@pytest.fixture
+def _raw_json_x(_common_arch):
+    return {
+        "name": "packagex",
+        "hash": "hash-of-x",
+        "prefix": "/path/to/packagex-install/",
+        "version": "1.0",
+        "arch": _common_arch.spec_json(),
+        "compiler": {"name": "gcc", "version": "10.2.0.2112"},
+        "dependencies": {"packagey": {"hash": "hash-of-y", "type": ["link"]}},
+        "parameters": {"precision": ["double", "float"]},
+    }
+
+
+def test_manifest_compatibility(_common_arch, _common_compiler, _raw_json_x):
     """Make sure that JsonSpecEntry outputs the expected JSON structure
     by comparing it with JSON parsed from an example string. This
     ensures that the testing objects like JsonSpecEntry produce the
@@ -164,7 +156,7 @@ def test_compatibility():
         hash="hash-of-y",
         prefix="/path/to/packagey-install/",
         version="1.0",
-        arch=_common_arch,
+        arch=_common_arch.spec_json(),
         compiler=_common_compiler.spec_json(),
         dependencies={},
         parameters={},
@@ -175,23 +167,44 @@ def test_compatibility():
         hash="hash-of-x",
         prefix="/path/to/packagex-install/",
         version="1.0",
-        arch=_common_arch,
+        arch=_common_arch.spec_json(),
         compiler=_common_compiler.spec_json(),
         dependencies=dict([y.as_dependency(deptypes=["link"])]),
         parameters={"precision": ["double", "float"]},
     )
 
     x_from_entry = x.to_dict()
-    x_from_str = json.loads(example_x_json_str)
-    assert x_from_entry == x_from_str
+    assert x_from_entry == _raw_json_x
 
 
 def test_compiler_from_entry():
-    compiler_data = json.loads(example_compiler_entry)
-    compiler_from_entry(compiler_data)
+    compiler_data = json.loads(
+        """\
+{
+  "name": "gcc",
+  "prefix": "/path/to/compiler/",
+  "version": "7.5.0",
+  "arch": {
+    "os": "centos8",
+    "target": "x86_64"
+  },
+  "executables": {
+    "cc": "/path/to/compiler/cc",
+    "cxx": "/path/to/compiler/cxx",
+    "fc": "/path/to/compiler/fc"
+  }
+}
+"""
+    )
+    compiler = compiler_from_entry(compiler_data, "/example/file")
+    assert compiler.cc == "/path/to/compiler/cc"
+    assert compiler.cxx == "/path/to/compiler/cxx"
+    assert compiler.fc == "/path/to/compiler/fc"
+    assert compiler.operating_system == "centos8"
 
 
-def generate_openmpi_entries():
+@pytest.fixture
+def generate_openmpi_entries(_common_arch, _common_compiler):
     """Generate two example JSON entries that refer to an OpenMPI
     installation and a hwloc dependency.
     """
@@ -202,7 +215,7 @@ def generate_openmpi_entries():
         hash="hwlocfakehashaaa",
         prefix="/path/to/hwloc-install/",
         version="2.0.3",
-        arch=_common_arch,
+        arch=_common_arch.spec_json(),
         compiler=_common_compiler.spec_json(),
         dependencies={},
         parameters={},
@@ -216,26 +229,25 @@ def generate_openmpi_entries():
         hash="openmpifakehasha",
         prefix="/path/to/openmpi-install/",
         version="4.1.0",
-        arch=_common_arch,
+        arch=_common_arch.spec_json(),
         compiler=_common_compiler.spec_json(),
         dependencies=dict([hwloc.as_dependency(deptypes=["link"])]),
         parameters={"internal-hwloc": False, "fabrics": ["psm"], "missing_variant": True},
     )
 
-    return [openmpi, hwloc]
+    return list(x.to_dict() for x in [openmpi, hwloc])
 
 
-def test_generate_specs_from_manifest():
+def test_generate_specs_from_manifest(generate_openmpi_entries):
     """Given JSON entries, check that we can form a set of Specs
     including dependency references.
     """
-    entries = list(x.to_dict() for x in generate_openmpi_entries())
-    specs = entries_to_specs(entries)
+    specs = entries_to_specs(generate_openmpi_entries)
     (openmpi_spec,) = list(x for x in specs.values() if x.name == "openmpi")
     assert openmpi_spec["hwloc"]
 
 
-def test_translate_cray_platform_to_linux(monkeypatch):
+def test_translate_cray_platform_to_linux(monkeypatch, _common_compiler):
     """Manifests might list specs on newer Cray platforms as being "cray",
     but Spack identifies such platforms as "linux". Make sure we
     automaticaly transform these entries.
@@ -247,13 +259,13 @@ def the_host_is_linux():
 
     monkeypatch.setattr(spack.platforms, "host", the_host_is_linux)
 
-    cray_arch = JsonArchEntry(platform="cray", os="rhel8", target="x86_64").to_dict()
+    cray_arch = JsonArchEntry(platform="cray", os="rhel8", target="x86_64")
     spec_json = JsonSpecEntry(
         name="cray-mpich",
         hash="craympichfakehashaaa",
         prefix="/path/to/cray-mpich/",
         version="1.0.0",
-        arch=cray_arch,
+        arch=cray_arch.spec_json(),
         compiler=_common_compiler.spec_json(),
         dependencies={},
         parameters={},
@@ -263,14 +275,15 @@ def the_host_is_linux():
     assert spec.architecture.platform == "linux"
 
 
-def test_translate_compiler_name():
+def test_translate_compiler_name(_common_arch):
     nvidia_compiler = JsonCompilerEntry(
         name="nvidia",
         version="19.1",
+        arch=_common_arch,
         executables={"cc": "/path/to/compiler/nvc", "cxx": "/path/to/compiler/nvc++"},
     )
 
-    compiler = compiler_from_entry(nvidia_compiler.compiler_json())
+    compiler = compiler_from_entry(nvidia_compiler.compiler_json(), "/example/file")
     assert compiler.name == "nvhpc"
 
     spec_json = JsonSpecEntry(
@@ -278,7 +291,7 @@ def test_translate_compiler_name():
         hash="hwlocfakehashaaa",
         prefix="/path/to/hwloc-install/",
         version="2.0.3",
-        arch=_common_arch,
+        arch=_common_arch.spec_json(),
         compiler=nvidia_compiler.spec_json(),
         dependencies={},
         parameters={},
@@ -288,18 +301,18 @@ def test_translate_compiler_name():
     assert spec.compiler.name == "nvhpc"
 
 
-def test_failed_translate_compiler_name():
+def test_failed_translate_compiler_name(_common_arch):
     unknown_compiler = JsonCompilerEntry(name="unknown", version="1.0")
 
     with pytest.raises(spack.compilers.UnknownCompilerError):
-        compiler_from_entry(unknown_compiler.compiler_json())
+        compiler_from_entry(unknown_compiler.compiler_json(), "/example/file")
 
     spec_json = JsonSpecEntry(
         name="packagey",
         hash="hash-of-y",
         prefix="/path/to/packagey-install/",
         version="1.0",
-        arch=_common_arch,
+        arch=_common_arch.spec_json(),
         compiler=unknown_compiler.spec_json(),
         dependencies={},
         parameters={},
@@ -309,7 +322,8 @@ def test_failed_translate_compiler_name():
         entries_to_specs([spec_json])
 
 
-def create_manifest_content():
+@pytest.fixture
+def manifest_content(generate_openmpi_entries, _common_compiler, _other_compiler):
     return {
         # Note: the cray_manifest module doesn't use the _meta section right
         # now, but it is anticipated to be useful
@@ -319,43 +333,70 @@ def create_manifest_content():
             "schema-version": "1.3",
             "cpe-version": "22.06",
         },
-        "specs": list(x.to_dict() for x in generate_openmpi_entries()),
-        "compilers": [_common_compiler.compiler_json()],
+        "specs": generate_openmpi_entries,
+        "compilers": [_common_compiler.compiler_json(), _other_compiler.compiler_json()],
     }
 
 
-@pytest.mark.only_original(
-    "The ASP-based concretizer is currently picky about OS matching and will fail."
-)
-def test_read_cray_manifest(tmpdir, mutable_config, mock_packages, mutable_database):
+def test_read_cray_manifest(
+    tmpdir, mutable_config, mock_packages, mutable_database, manifest_content
+):
     """Check that (a) we can read the cray manifest and add it to the Spack
     Database and (b) we can concretize specs based on that.
     """
     with tmpdir.as_cwd():
         test_db_fname = "external-db.json"
         with open(test_db_fname, "w") as db_file:
-            json.dump(create_manifest_content(), db_file)
+            json.dump(manifest_content, db_file)
         cray_manifest.read(test_db_fname, True)
         query_specs = spack.store.STORE.db.query("openmpi")
         assert any(x.dag_hash() == "openmpifakehasha" for x in query_specs)
 
         concretized_specs = spack.cmd.parse_specs(
-            "depends-on-openmpi %gcc@4.5.0 arch=test-redhat6-x86_64" " ^/openmpifakehasha".split(),
-            concretize=True,
+            "depends-on-openmpi ^/openmpifakehasha".split(), concretize=True
         )
         assert concretized_specs[0]["hwloc"].dag_hash() == "hwlocfakehashaaa"
 
 
-@pytest.mark.only_original(
-    "The ASP-based concretizer is currently picky about OS matching and will fail."
-)
+def test_read_cray_manifest_add_compiler_failure(
+    tmpdir, mutable_config, mock_packages, mutable_database, manifest_content, monkeypatch
+):
+    """Check that cray manifest can be read even if some compilers cannot
+    be added.
+    """
+    orig_add_compilers_to_config = spack.compilers.add_compilers_to_config
+
+    class fail_for_clang:
+        def __init__(self):
+            self.called_with_clang = False
+
+        def __call__(self, compilers, **kwargs):
+            if any(x.name == "clang" for x in compilers):
+                self.called_with_clang = True
+                raise Exception()
+            return orig_add_compilers_to_config(compilers, **kwargs)
+
+    checker = fail_for_clang()
+    monkeypatch.setattr(spack.compilers, "add_compilers_to_config", checker)
+
+    with tmpdir.as_cwd():
+        test_db_fname = "external-db.json"
+        with open(test_db_fname, "w") as db_file:
+            json.dump(manifest_content, db_file)
+        cray_manifest.read(test_db_fname, True)
+        query_specs = spack.store.STORE.db.query("openmpi")
+        assert any(x.dag_hash() == "openmpifakehasha" for x in query_specs)
+
+    assert checker.called_with_clang
+
+
 def test_read_cray_manifest_twice_no_compiler_duplicates(
-    tmpdir, mutable_config, mock_packages, mutable_database
+    tmpdir, mutable_config, mock_packages, mutable_database, manifest_content
 ):
     with tmpdir.as_cwd():
         test_db_fname = "external-db.json"
         with open(test_db_fname, "w") as db_file:
-            json.dump(create_manifest_content(), db_file)
+            json.dump(manifest_content, db_file)
 
         # Read the manifest twice
         cray_manifest.read(test_db_fname, True)
@@ -363,7 +404,7 @@ def test_read_cray_manifest_twice_no_compiler_duplicates(
 
         compilers = spack.compilers.all_compilers()
         filtered = list(
-            c for c in compilers if c.spec == spack.spec.CompilerSpec("gcc@=10.2.0.cray")
+            c for c in compilers if c.spec == spack.spec.CompilerSpec("gcc@=10.2.0.2112")
         )
         assert len(filtered) == 1
 
@@ -423,3 +464,27 @@ def test_convert_validation_error(tmpdir, mutable_config, mock_packages, mutable
     with pytest.raises(cray_manifest.ManifestValidationError) as e:
         cray_manifest.read(invalid_schema_path, True)
     str(e)
+
+
+@pytest.fixture
+def directory_with_manifest(tmpdir, manifest_content):
+    """Create a manifest file in a directory. Used by 'spack external'."""
+    with tmpdir.as_cwd():
+        test_db_fname = "external-db.json"
+        with open(test_db_fname, "w") as db_file:
+            json.dump(manifest_content, db_file)
+
+    yield str(tmpdir)
+
+
+def test_find_external_nonempty_default_manifest_dir(
+    mutable_database, mutable_mock_repo, tmpdir, monkeypatch, directory_with_manifest
+):
+    """The user runs 'spack external find'; the default manifest directory
+    contains a manifest file. Ensure that the specs are read.
+    """
+    monkeypatch.setenv("PATH", "")
+    monkeypatch.setattr(spack.cray_manifest, "default_path", str(directory_with_manifest))
+    spack.cmd.external._collect_and_consume_cray_manifest_files(ignore_default_dir=False)
+    specs = spack.store.STORE.db.query("hwloc")
+    assert any(x.dag_hash() == "hwlocfakehashaaa" for x in specs)
diff --git a/lib/spack/spack/test/installer.py b/lib/spack/spack/test/installer.py
index 91f695dd70a..6b42e591eb9 100644
--- a/lib/spack/spack/test/installer.py
+++ b/lib/spack/spack/test/installer.py
@@ -20,6 +20,7 @@
 import spack.concretize
 import spack.config
 import spack.database
+import spack.deptypes as dt
 import spack.installer as inst
 import spack.package_base
 import spack.package_prefs as prefs
@@ -1388,6 +1389,26 @@ def test_single_external_implicit_install(install_mockery, explicit_args, is_exp
     assert spack.store.STORE.db.get_record(pkg).explicit == is_explicit
 
 
+def test_overwrite_install_does_install_build_deps(install_mockery, mock_fetch):
+    """When overwrite installing something from sources, build deps should be installed."""
+    s = spack.spec.Spec("dtrun3").concretized()
+    create_installer([(s, {})]).install()
+
+    # Verify there is a pure build dep
+    edge = s.edges_to_dependencies(name="dtbuild3").pop()
+    assert edge.depflag == dt.BUILD
+    build_dep = edge.spec
+
+    # Uninstall the build dep
+    build_dep.package.do_uninstall()
+
+    # Overwrite install the root dtrun3
+    create_installer([(s, {"overwrite": [s.dag_hash()]})]).install()
+
+    # Verify that the build dep was also installed.
+    assert build_dep.installed
+
+
 @pytest.mark.parametrize("run_tests", [True, False])
 def test_print_install_test_log_skipped(install_mockery, mock_packages, capfd, run_tests):
     """Confirm printing of install log skipped if not run/no failures."""
diff --git a/lib/spack/spack/test/repo.py b/lib/spack/spack/test/repo.py
index 7314beebb5c..eb6b1239162 100644
--- a/lib/spack/spack/test/repo.py
+++ b/lib/spack/spack/test/repo.py
@@ -181,3 +181,15 @@ def test_repository_construction_doesnt_use_globals(nullify_globals, repo_paths,
     repo_path = spack.repo.RepoPath(*repo_paths)
     assert len(repo_path.repos) == len(namespaces)
     assert [x.namespace for x in repo_path.repos] == namespaces
+
+
+@pytest.mark.parametrize("method_name", ["dirname_for_package_name", "filename_for_package_name"])
+def test_path_computation_with_names(method_name, mock_repo_path):
+    """Tests that repositories can compute the correct paths when using both fully qualified
+    names and unqualified names.
+    """
+    repo_path = spack.repo.RepoPath(mock_repo_path)
+    method = getattr(repo_path, method_name)
+    unqualified = method("mpileaks")
+    qualified = method("builtin.mock.mpileaks")
+    assert qualified == unqualified
diff --git a/share/spack/gitlab/cloud_pipelines/.gitlab-ci.yml b/share/spack/gitlab/cloud_pipelines/.gitlab-ci.yml
index d7f8a38ef63..a9a9fee13c0 100644
--- a/share/spack/gitlab/cloud_pipelines/.gitlab-ci.yml
+++ b/share/spack/gitlab/cloud_pipelines/.gitlab-ci.yml
@@ -827,16 +827,16 @@ e4s-cray-rhel-build:
   variables:
     SPACK_CI_STACK_NAME: e4s-cray-sles
 
-# e4s-cray-sles-generate:
-#   extends: [ ".generate-cray-sles", ".e4s-cray-sles" ]
+e4s-cray-sles-generate:
+  extends: [ ".generate-cray-sles", ".e4s-cray-sles" ]
 
-# e4s-cray-sles-build:
-#   extends: [ ".build", ".e4s-cray-sles" ]
-#   trigger:
-#     include:
-#       - artifact: jobs_scratch_dir/cloud-ci-pipeline.yml
-#         job: e4s-cray-sles-generate
-#     strategy: depend
-#   needs:
-#     - artifacts: True
-#       job: e4s-cray-sles-generate
+e4s-cray-sles-build:
+  extends: [ ".build", ".e4s-cray-sles" ]
+  trigger:
+    include:
+      - artifact: jobs_scratch_dir/cloud-ci-pipeline.yml
+        job: e4s-cray-sles-generate
+    strategy: depend
+  needs:
+    - artifacts: True
+      job: e4s-cray-sles-generate
diff --git a/share/spack/spack-completion.bash b/share/spack/spack-completion.bash
index 1983b960d54..b9521b8f0cf 100755
--- a/share/spack/spack-completion.bash
+++ b/share/spack/spack-completion.bash
@@ -423,7 +423,7 @@ _spack_audit() {
     then
         SPACK_COMPREPLY="-h --help"
     else
-        SPACK_COMPREPLY="configs packages-https packages list"
+        SPACK_COMPREPLY="configs externals packages-https packages list"
     fi
 }
 
@@ -431,6 +431,15 @@ _spack_audit_configs() {
     SPACK_COMPREPLY="-h --help"
 }
 
+_spack_audit_externals() {
+    if $list_options
+    then
+        SPACK_COMPREPLY="-h --help --list"
+    else
+        SPACK_COMPREPLY=""
+    fi
+}
+
 _spack_audit_packages_https() {
     if $list_options
     then
diff --git a/share/spack/spack-completion.fish b/share/spack/spack-completion.fish
index c5da416817c..f4ac310adac 100755
--- a/share/spack/spack-completion.fish
+++ b/share/spack/spack-completion.fish
@@ -508,6 +508,7 @@ complete -c spack -n '__fish_spack_using_command arch' -s b -l backend -d 'print
 # spack audit
 set -g __fish_spack_optspecs_spack_audit h/help
 complete -c spack -n '__fish_spack_using_command_pos 0 audit' -f -a configs -d 'audit configuration files'
+complete -c spack -n '__fish_spack_using_command_pos 0 audit' -f -a externals -d 'check external detection in packages'
 complete -c spack -n '__fish_spack_using_command_pos 0 audit' -f -a packages-https -d 'check https in packages'
 complete -c spack -n '__fish_spack_using_command_pos 0 audit' -f -a packages -d 'audit package recipes'
 complete -c spack -n '__fish_spack_using_command_pos 0 audit' -f -a list -d 'list available checks and exits'
@@ -519,6 +520,14 @@ set -g __fish_spack_optspecs_spack_audit_configs h/help
 complete -c spack -n '__fish_spack_using_command audit configs' -s h -l help -f -a help
 complete -c spack -n '__fish_spack_using_command audit configs' -s h -l help -d 'show this help message and exit'
 
+# spack audit externals
+set -g __fish_spack_optspecs_spack_audit_externals h/help list
+complete -c spack -n '__fish_spack_using_command_pos_remainder 0 audit externals' -f -a '(__fish_spack_packages)'
+complete -c spack -n '__fish_spack_using_command audit externals' -s h -l help -f -a help
+complete -c spack -n '__fish_spack_using_command audit externals' -s h -l help -d 'show this help message and exit'
+complete -c spack -n '__fish_spack_using_command audit externals' -l list -f -a list_externals
+complete -c spack -n '__fish_spack_using_command audit externals' -l list -d 'if passed, list which packages have detection tests'
+
 # spack audit packages-https
 set -g __fish_spack_optspecs_spack_audit_packages_https h/help all
 complete -c spack -n '__fish_spack_using_command_pos_remainder 0 audit packages-https' -f -a '(__fish_spack_packages)'
diff --git a/var/spack/repos/builtin/packages/gcc/detection_test.yaml b/var/spack/repos/builtin/packages/gcc/detection_test.yaml
new file mode 100644
index 00000000000..0930f82d936
--- /dev/null
+++ b/var/spack/repos/builtin/packages/gcc/detection_test.yaml
@@ -0,0 +1,38 @@
+paths:
+  # Ubuntu 18.04, system compilers without Fortran
+  - layout:
+      - executables:
+        - "bin/gcc"
+        - "bin/g++"
+        script: "echo 7.5.0"
+    results:
+      - spec: "gcc@7.5.0 languages=c,c++"
+  # Mock a version < 7 of GCC that requires -dumpversion and
+  # errors with -dumpfullversion
+  - layout:
+      - executables:
+        - "bin/gcc-5"
+        - "bin/g++-5"
+        - "bin/gfortran-5"
+        script: |
+          if [[ "$1" == "-dumpversion" ]] ; then
+            echo "5.5.0"
+          else
+            echo "gcc-5: fatal error: no input files"
+            echo "compilation terminated."
+            exit 1
+          fi
+    results:
+      - spec: "gcc@5.5.0 languages=c,c++,fortran"
+  # Multiple compilers present at the same time
+  - layout:
+      - executables:
+        - "bin/x86_64-linux-gnu-gcc-6"
+        script: 'echo 6.5.0'
+      - executables:
+        - "bin/x86_64-linux-gnu-gcc-10"
+        - "bin/x86_64-linux-gnu-g++-10"
+        script: "echo 10.1.0"
+    results:
+      - spec: "gcc@6.5.0 languages=c"
+      - spec: "gcc@10.1.0 languages=c,c++"
diff --git a/var/spack/repos/builtin/packages/hpctoolkit/package.py b/var/spack/repos/builtin/packages/hpctoolkit/package.py
index a6ae716bb73..8d58956508a 100644
--- a/var/spack/repos/builtin/packages/hpctoolkit/package.py
+++ b/var/spack/repos/builtin/packages/hpctoolkit/package.py
@@ -27,6 +27,8 @@ class Hpctoolkit(AutotoolsPackage):
     test_requires_compiler = True
 
     version("develop", branch="develop")
+    version("2023.08.stable", branch="release/2023.08")
+    version("2023.08.1", tag="2023.08.1", commit="753a72affd584a5e72fe153d1e8c47a394a3886e")
     version("2023.03.stable", branch="release/2023.03")
     version("2023.03.01", commit="9e0daf2ad169f6c7f6c60408475b3c2f71baebbf")
     version("2022.10.01", commit="e8a5cc87e8f5ddfd14338459a4106f8e0d162c83")
diff --git a/var/spack/repos/builtin/packages/intel/detection_test.yaml b/var/spack/repos/builtin/packages/intel/detection_test.yaml
new file mode 100644
index 00000000000..076bfeaabac
--- /dev/null
+++ b/var/spack/repos/builtin/packages/intel/detection_test.yaml
@@ -0,0 +1,19 @@
+paths:
+  - layout:
+      - executables:
+        - "bin/intel64/icc"
+        script: |
+          echo "icc (ICC) 18.0.5 20180823"
+          echo "Copyright (C) 1985-2018 Intel Corporation.  All rights reserved."
+      - executables:
+        - "bin/intel64/icpc"
+        script: |
+          echo "icpc (ICC) 18.0.5 20180823"
+          echo "Copyright (C) 1985-2018 Intel Corporation.  All rights reserved."
+      - executables:
+        - "bin/intel64/ifort"
+        script: |
+          echo "ifort (IFORT) 18.0.5 20180823"
+          echo "Copyright (C) 1985-2018 Intel Corporation.  All rights reserved."
+    results:
+      - spec: 'intel@18.0.5'
diff --git a/var/spack/repos/builtin/packages/kokkos-nvcc-wrapper/package.py b/var/spack/repos/builtin/packages/kokkos-nvcc-wrapper/package.py
index 463f3132f41..1ecc52340c5 100644
--- a/var/spack/repos/builtin/packages/kokkos-nvcc-wrapper/package.py
+++ b/var/spack/repos/builtin/packages/kokkos-nvcc-wrapper/package.py
@@ -19,6 +19,7 @@ class KokkosNvccWrapper(Package):
 
     maintainers("Rombur")
 
+    version("4.1.00", sha256="cf725ea34ba766fdaf29c884cfe2daacfdc6dc2d6af84042d1c78d0f16866275")
     version("4.0.01", sha256="bb942de8afdd519fd6d5d3974706bfc22b6585a62dd565c12e53bdb82cd154f0")
     version("4.0.00", sha256="1829a423883d4b44223c7c3a53d3c51671145aad57d7d23e6a1a4bebf710dcf6")
     version("3.7.02", sha256="5024979f06bc8da2fb696252a66297f3e0e67098595a0cc7345312b3b4aa0f54")
diff --git a/var/spack/repos/builtin/packages/libcatalyst/package.py b/var/spack/repos/builtin/packages/libcatalyst/package.py
index ed7aa445783..9000ca137fc 100644
--- a/var/spack/repos/builtin/packages/libcatalyst/package.py
+++ b/var/spack/repos/builtin/packages/libcatalyst/package.py
@@ -3,6 +3,10 @@
 #
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
 
+import subprocess
+
+import llnl.util.tty as tty
+
 from spack.package import *
 
 
@@ -14,25 +18,47 @@ class Libcatalyst(CMakePackage):
     git = "https://gitlab.kitware.com/paraview/catalyst.git"
     url = "https://gitlab.kitware.com/api/v4/projects/paraview%2Fcatalyst/packages/generic/catalyst/v2.0.0/catalyst-v2.0.0.tar.gz"
 
-    maintainers("mathstuf")
-
-    version("2.0.0-rc3", sha256="8862bd0a4d0be2176b4272f9affda1ea4e5092087acbb99a2fe2621c33834e05")
-
-    # master as of 2021-05-12
-    version("0.20210512", commit="8456ccd6015142b5a7705f79471361d4f5644fa7")
+    maintainers("mathstuf", "ayenpure")
+    version("master", branch="master")
+    version("2.0.0-rc4", sha256="cb491e4ccd344156cc2494f65b9f38885598c16d12e1016c36e2ee0bc3640863")
 
     variant("mpi", default=False, description="Enable MPI support")
+    variant("conduit", default=False, description="Use external Conduit for Catalyst")
 
     depends_on("mpi", when="+mpi")
-
-    # TODO: catalyst doesn't support an external conduit
-    # depends_on('conduit')
+    depends_on("conduit", when="+conduit")
 
     def cmake_args(self):
         """Populate cmake arguments for libcatalyst."""
         args = [
             "-DCATALYST_BUILD_TESTING=OFF",
             self.define_from_variant("CATALYST_USE_MPI", "mpi"),
+            self.define_from_variant("CATALYST_WITH_EXTERNAL_CONDUIT", "conduit"),
         ]
 
         return args
+
+    def setup_run_environment(self, env):
+        spec = self.spec
+        if spec.satisfies("+conduit"):
+            env.prepend_path("CMAKE_PREFIX_PATH", spec["conduit"].prefix)
+
+    @on_package_attributes(run_tests=True)
+    @run_after("install")
+    def build_test(self):
+        testdir = "smoke_test_build"
+        cmakeExampleDir = join_path(self.stage.source_path, "examples")
+        cmake_args = [
+            cmakeExampleDir,
+            "-DBUILD_SHARED_LIBS=ON",
+            self.define("CMAKE_PREFIX_PATH", self.prefix),
+        ]
+        cmake = which(self.spec["cmake"].prefix.bin.cmake)
+
+        with working_dir(testdir, create=True):
+            cmake(*cmake_args)
+            cmake(*(["--build", "."]))
+            tty.info("Running Catalyst test")
+
+            res = subprocess.run(["adaptor0/adaptor0_test", "catalyst"])
+            assert res.returncode == 0
diff --git a/var/spack/repos/builtin/packages/llvm/detection_test.yaml b/var/spack/repos/builtin/packages/llvm/detection_test.yaml
new file mode 100644
index 00000000000..48e9d6751af
--- /dev/null
+++ b/var/spack/repos/builtin/packages/llvm/detection_test.yaml
@@ -0,0 +1,56 @@
+paths:
+  - layout:
+      - executables:
+        - "bin/clang-3.9"
+        script: |
+          echo "clang version 3.9.1-19ubuntu1 (tags/RELEASE_391/rc2)"
+          echo "Target: x86_64-pc-linux-gnu"
+          echo "Thread model: posix"
+          echo "InstalledDir: /usr/bin"
+      - executables:
+        - "bin/clang++-3.9"
+        script: |
+          echo "clang version 3.9.1-19ubuntu1 (tags/RELEASE_391/rc2)"
+          echo "Target: x86_64-pc-linux-gnu"
+          echo "Thread model: posix"
+          echo "InstalledDir: /usr/bin"
+    results:
+      - spec: 'llvm@3.9.1 +clang~lld~lldb'
+  # Multiple LLVM packages in the same prefix
+  - layout:
+      - executables:
+        - "bin/clang-8"
+        - "bin/clang++-8"
+        script: |
+          echo "clang version 8.0.0-3~ubuntu18.04.2 (tags/RELEASE_800/final)"
+          echo "Target: x86_64-pc-linux-gnu"
+          echo "Thread model: posix"
+          echo "InstalledDir: /usr/bin"
+      - executables:
+        - "bin/ld.lld-8"
+        script: 'echo "LLD 8.0.0 (compatible with GNU linkers)"'
+      - executables:
+        - "bin/lldb"
+        script: 'echo "lldb version 8.0.0"'
+      - executables:
+        - "bin/clang-3.9"
+        - "bin/clang++-3.9"
+        script: |
+          echo "clang version 3.9.1-19ubuntu1 (tags/RELEASE_391/rc2)"
+          echo "Target: x86_64-pc-linux-gnu"
+          echo "Thread model: posix"
+          echo "InstalledDir: /usr/bin"
+    results:
+      - spec: 'llvm@8.0.0+clang+lld+lldb'
+      - spec: 'llvm@3.9.1+clang~lld~lldb'
+  # Apple Clang should not be detected
+  - layout:
+    - executables:
+      - "bin/clang"
+      - "bin/clang++"
+      script: |
+        echo "Apple clang version 11.0.0 (clang-1100.0.33.8)"
+        echo "Target: x86_64-apple-darwin19.5.0"
+        echo "Thread model: posix"
+        echo "InstalledDir: /Library/Developer/CommandLineTools/usr/bin"
+    results: []
diff --git a/var/spack/repos/builtin/packages/modeltest-ng/package.py b/var/spack/repos/builtin/packages/modeltest-ng/package.py
index 55d1bd1ff60..7a2b4dcc2c2 100644
--- a/var/spack/repos/builtin/packages/modeltest-ng/package.py
+++ b/var/spack/repos/builtin/packages/modeltest-ng/package.py
@@ -13,8 +13,9 @@ class ModeltestNg(CMakePackage):
     url = "https://github.com/ddarriba/modeltest/archive/refs/tags/v0.1.7.tar.gz"
     git = "https://github.com/ddarriba/modeltest.git"
 
-    maintainers("dorton21")
+    maintainers("snehring")
 
+    version("20220721", commit="1066356b984100897b8bd38ac771c5c950984c01", submodules=True)
     version("0.1.7", commit="cc028888f1d4222aaa53b99c6b02cd934a279001", submodules=True)
 
     variant("mpi", default=False, description="Enable MPI")
@@ -24,5 +25,12 @@ class ModeltestNg(CMakePackage):
     depends_on("flex", type="build")
     depends_on("openmpi", when="+mpi")
 
+    # 40217: ICE by gcc-toolset-12-gcc-12.2.1-7.4.el8.aarch64 of Rocky Linux 8.8:
+    conflicts("%gcc@12.2.0:12.2", when="target=aarch64:", msg="ICE with gcc@12.2 on aarch64")
+
+    requires(
+        "@20220721:", when="target=aarch64:", msg="Support for aarch64 was added after 20220721."
+    )
+
     def cmake_args(self):
         return [self.define_from_variant("ENABLE_MPI", "mpi")]
diff --git a/var/spack/repos/builtin/packages/openblas/package.py b/var/spack/repos/builtin/packages/openblas/package.py
index e194a366e47..43c3dafdade 100644
--- a/var/spack/repos/builtin/packages/openblas/package.py
+++ b/var/spack/repos/builtin/packages/openblas/package.py
@@ -274,7 +274,7 @@ def libs(self):
         search_shared = bool(spec.variants["shared"].value)
         suffix = spec.variants["symbol_suffix"].value
         if suffix != "none":
-            name += suffix
+            name = [x + suffix for x in name]
 
         return find_libraries(name, spec.prefix, shared=search_shared, recursive=True)