Inject dependencies in repo classes (#45053)

16 files changed, 317 insertions, 176 deletions

diff --git a/lib/spack/spack/caches.py b/lib/spack/spack/caches.py
index 19c736748e..14d03a14b3 100644
--- a/lib/spack/spack/caches.py
+++ b/lib/spack/spack/caches.py
@@ -34,6 +34,8 @@ def _misc_cache():
     return spack.util.file_cache.FileCache(path)
 
 
+FileCacheType = Union[spack.util.file_cache.FileCache, llnl.util.lang.Singleton]
+
 #: Spack's cache for small data
 MISC_CACHE: Union[spack.util.file_cache.FileCache, llnl.util.lang.Singleton] = (
     llnl.util.lang.Singleton(_misc_cache)
diff --git a/lib/spack/spack/cmd/create.py b/lib/spack/spack/cmd/create.py
index 49f4ae2177..0481b9d044 100644
--- a/lib/spack/spack/cmd/create.py
+++ b/lib/spack/spack/cmd/create.py
@@ -2,7 +2,6 @@
 # Spack Project Developers. See the top-level COPYRIGHT file for details.
 #
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
-
 import os
 import re
 import sys
@@ -934,7 +933,7 @@ def get_repository(args, name):
     # Figure out where the new package should live
     repo_path = args.repo
     if repo_path is not None:
-        repo = spack.repo.Repo(repo_path)
+        repo = spack.repo.from_path(repo_path)
         if spec.namespace and spec.namespace != repo.namespace:
             tty.die(
                 "Can't create package with namespace {0} in repo with "
diff --git a/lib/spack/spack/cmd/edit.py b/lib/spack/spack/cmd/edit.py
index e7d64c77ea..9951bb65a3 100644
--- a/lib/spack/spack/cmd/edit.py
+++ b/lib/spack/spack/cmd/edit.py
@@ -123,7 +123,7 @@ def edit(parser, args):
         spack.util.editor.editor(*paths)
     elif names:
         if args.repo:
-            repo = spack.repo.Repo(args.repo)
+            repo = spack.repo.from_path(args.repo)
         elif args.namespace:
             repo = spack.repo.PATH.get_repo(args.namespace)
         else:
diff --git a/lib/spack/spack/cmd/repo.py b/lib/spack/spack/cmd/repo.py
index 68af91cd91..e41e21f0a5 100644
--- a/lib/spack/spack/cmd/repo.py
+++ b/lib/spack/spack/cmd/repo.py
@@ -91,7 +91,7 @@ def repo_add(args):
         tty.die("Not a Spack repository: %s" % path)
 
     # Make sure it's actually a spack repository by constructing it.
-    repo = spack.repo.Repo(canon_path)
+    repo = spack.repo.from_path(canon_path)
 
     # If that succeeds, finally add it to the configuration.
     repos = spack.config.get("repos", scope=args.scope)
@@ -124,7 +124,7 @@ def repo_remove(args):
     # If it is a namespace, remove corresponding repo
     for path in repos:
         try:
-            repo = spack.repo.Repo(path)
+            repo = spack.repo.from_path(path)
             if repo.namespace == namespace_or_path:
                 repos.remove(path)
                 spack.config.set("repos", repos, args.scope)
@@ -142,7 +142,7 @@ def repo_list(args):
     repos = []
     for r in roots:
         try:
-            repos.append(spack.repo.Repo(r))
+            repos.append(spack.repo.from_path(r))
         except spack.repo.RepoError:
             continue
 
diff --git a/lib/spack/spack/environment/environment.py b/lib/spack/spack/environment/environment.py
index 32aff3e238..7643579f16 100644
--- a/lib/spack/spack/environment/environment.py
+++ b/lib/spack/spack/environment/environment.py
@@ -24,6 +24,7 @@ import llnl.util.tty.color as clr
 from llnl.util.link_tree import ConflictingSpecsError
 from llnl.util.symlink import readlink, symlink
 
+import spack.caches
 import spack.cmd
 import spack.compilers
 import spack.concretize
@@ -2542,7 +2543,7 @@ def _concretize_task(packed_arguments) -> Tuple[int, Spec, float]:
 
 def make_repo_path(root):
     """Make a RepoPath from the repo subdirectories in an environment."""
-    path = spack.repo.RepoPath()
+    path = spack.repo.RepoPath(cache=spack.caches.MISC_CACHE)
 
     if os.path.isdir(root):
         for repo_root in os.listdir(root):
@@ -2551,7 +2552,7 @@ def make_repo_path(root):
             if not os.path.isdir(repo_root):
                 continue
 
-            repo = spack.repo.Repo(repo_root)
+            repo = spack.repo.from_path(repo_root)
             path.put_last(repo)
 
     return path
diff --git a/lib/spack/spack/installer.py b/lib/spack/spack/installer.py
index 65c3e78553..dc94c95926 100644
--- a/lib/spack/spack/installer.py
+++ b/lib/spack/spack/installer.py
@@ -582,7 +582,7 @@ def dump_packages(spec: "spack.spec.Spec", path: str) -> None:
 
             # Create a source repo and get the pkg directory out of it.
             try:
-                source_repo = spack.repo.Repo(source_repo_root)
+                source_repo = spack.repo.from_path(source_repo_root)
                 source_pkg_dir = source_repo.dirname_for_package_name(node.name)
             except spack.repo.RepoError as err:
                 tty.debug(f"Failed to create source repo for {node.name}: {str(err)}")
@@ -593,7 +593,7 @@ def dump_packages(spec: "spack.spec.Spec", path: str) -> None:
         dest_repo_root = os.path.join(path, node.namespace)
         if not os.path.exists(dest_repo_root):
             spack.repo.create_repo(dest_repo_root)
-        repo = spack.repo.Repo(dest_repo_root)
+        repo = spack.repo.from_path(dest_repo_root)
 
         # Get the location of the package in the dest repo.
         dest_pkg_dir = repo.dirname_for_package_name(node.name)
diff --git a/lib/spack/spack/package_base.py b/lib/spack/spack/package_base.py
index 30aeb0bd7c..50ea97a9d4 100644
--- a/lib/spack/spack/package_base.py
+++ b/lib/spack/spack/package_base.py
@@ -748,11 +748,6 @@ class PackageBase(WindowsRPath, PackageViewMixin, RedistributionMixin, metaclass
         self._fetch_time = 0.0
 
         self.win_rpath = fsys.WindowsSimulatedRPath(self)
-
-        if self.is_extension:
-            pkg_cls = spack.repo.PATH.get_pkg_class(self.extendee_spec.name)
-            pkg_cls(self.extendee_spec)._check_extendable()
-
         super().__init__()
 
     @classmethod
@@ -2388,10 +2383,6 @@ class PackageBase(WindowsRPath, PackageViewMixin, RedistributionMixin, metaclass
         PackageBase.uninstall_by_spec(spec, force=True, deprecator=deprecator)
         link_fn(deprecator.prefix, spec.prefix)
 
-    def _check_extendable(self):
-        if not self.extendable:
-            raise ValueError("Package %s is not extendable!" % self.name)
-
     def view(self):
         """Create a view with the prefix of this package as the root.
         Extensions added to this view will modify the installation prefix of
diff --git a/lib/spack/spack/repo.py b/lib/spack/spack/repo.py
index 743f5a18e8..f3394a118c 100644
--- a/lib/spack/spack/repo.py
+++ b/lib/spack/spack/repo.py
@@ -25,7 +25,8 @@ import sys
 import traceback
 import types
 import uuid
-from typing import Any, Dict, List, Set, Tuple, Union
+import warnings
+from typing import Any, Dict, Generator, List, Optional, Set, Tuple, Type, Union
 
 import llnl.path
 import llnl.util.filesystem as fs
@@ -126,11 +127,35 @@ class SpackNamespaceLoader:
 
 
 class ReposFinder:
-    """MetaPathFinder class that loads a Python module corresponding to a Spack package
+    """MetaPathFinder class that loads a Python module corresponding to a Spack package.
 
-    Return a loader based on the inspection of the current global repository list.
+    Returns a loader based on the inspection of the current repository list.
     """
 
+    def __init__(self):
+        self._repo_init = _path
+        self._repo = None
+
+    @property
+    def current_repository(self):
+        if self._repo is None:
+            self._repo = self._repo_init()
+        return self._repo
+
+    @current_repository.setter
+    def current_repository(self, value):
+        self._repo = value
+
+    @contextlib.contextmanager
+    def switch_repo(self, substitute: "RepoType"):
+        """Switch the current repository list for the duration of the context manager."""
+        old = self.current_repository
+        try:
+            self.current_repository = substitute
+            yield
+        finally:
+            self.current_repository = old
+
     def find_spec(self, fullname, python_path, target=None):
         # "target" is not None only when calling importlib.reload()
         if target is not None:
@@ -149,9 +174,14 @@ class ReposFinder:
         # namespaces are added to repo, and package modules are leaves.
         namespace, dot, module_name = fullname.rpartition(".")
 
-        # If it's a module in some repo, or if it is the repo's
-        # namespace, let the repo handle it.
-        for repo in PATH.repos:
+        # If it's a module in some repo, or if it is the repo's namespace, let the repo handle it.
+        is_repo_path = isinstance(self.current_repository, RepoPath)
+        if is_repo_path:
+            repos = self.current_repository.repos
+        else:
+            repos = [self.current_repository]
+
+        for repo in 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
@@ -165,7 +195,7 @@ class ReposFinder:
 
         # No repo provides the namespace, but it is a valid prefix of
         # something in the RepoPath.
-        if PATH.by_namespace.is_prefix(fullname):
+        if is_repo_path and self.current_repository.by_namespace.is_prefix(fullname):
             return SpackNamespaceLoader()
 
         return None
@@ -560,7 +590,7 @@ class RepoIndex:
         self,
         package_checker: FastPackageChecker,
         namespace: str,
-        cache: spack.util.file_cache.FileCache,
+        cache: spack.caches.FileCacheType,
     ):
         self.checker = package_checker
         self.packages_path = self.checker.packages_path
@@ -648,11 +678,9 @@ class RepoPath:
         repos (list): list Repo objects or paths to put in this RepoPath
     """
 
-    def __init__(self, *repos, **kwargs):
-        cache = kwargs.get("cache", spack.caches.MISC_CACHE)
+    def __init__(self, *repos, cache, overrides=None):
         self.repos = []
         self.by_namespace = nm.NamespaceTrie()
-
         self._provider_index = None
         self._patch_index = None
         self._tag_index = None
@@ -661,7 +689,8 @@ class RepoPath:
         for repo in repos:
             try:
                 if isinstance(repo, str):
-                    repo = Repo(repo, cache=cache)
+                    repo = Repo(repo, cache=cache, overrides=overrides)
+                repo.finder(self)
                 self.put_last(repo)
             except RepoError as e:
                 tty.warn(
@@ -915,18 +944,28 @@ class Repo:
     Each package repository must have a top-level configuration file
     called `repo.yaml`.
 
-    Currently, `repo.yaml` this must define:
+    Currently, `repo.yaml` must define:
 
     `namespace`:
         A Python namespace where the repository's packages should live.
 
+    `subdirectory`:
+        An optional subdirectory name where packages are placed
     """
 
-    def __init__(self, root, cache=None):
+    def __init__(
+        self,
+        root: str,
+        *,
+        cache: spack.caches.FileCacheType,
+        overrides: Optional[Dict[str, Any]] = None,
+    ) -> None:
         """Instantiate a package repository from a filesystem path.
 
         Args:
             root: the root directory of the repository
+            cache: file cache associated with this repository
+            overrides: dict mapping package name to class attribute overrides for that package
         """
         # Root directory, containing _repo.yaml and package dirs
         # Allow roots to by spack-relative by starting with '$spack'
@@ -939,20 +978,20 @@ class Repo:
 
         # Validate repository layout.
         self.config_file = os.path.join(self.root, repo_config_name)
-        check(os.path.isfile(self.config_file), "No %s found in '%s'" % (repo_config_name, root))
+        check(os.path.isfile(self.config_file), f"No {repo_config_name} found in '{root}'")
 
         # Read configuration and validate namespace
         config = self._read_config()
         check(
             "namespace" in config,
-            "%s must define a namespace." % os.path.join(root, repo_config_name),
+            f"{os.path.join(root, repo_config_name)} must define a namespace.",
         )
 
         self.namespace = config["namespace"]
         check(
             re.match(r"[a-zA-Z][a-zA-Z0-9_.]+", self.namespace),
-            ("Invalid namespace '%s' in repo '%s'. " % (self.namespace, self.root))
-            + "Namespaces must be valid python identifiers separated by '.'",
+            f"Invalid namespace '{self.namespace}' in repo '{self.root}'. "
+            "Namespaces must be valid python identifiers separated by '.'",
         )
 
         # Set up 'full_namespace' to include the super-namespace
@@ -964,23 +1003,26 @@ class Repo:
         packages_dir = config.get("subdirectory", packages_dir_name)
         self.packages_path = os.path.join(self.root, packages_dir)
         check(
-            os.path.isdir(self.packages_path),
-            "No directory '%s' found in '%s'" % (packages_dir, root),
+            os.path.isdir(self.packages_path), f"No directory '{packages_dir}' found in '{root}'"
         )
 
-        # These are internal cache variables.
-        self._modules = {}
-        self._classes = {}
-        self._instances = {}
+        # Class attribute overrides by package name
+        self.overrides = overrides or {}
+
+        # Optional reference to a RepoPath to influence module import from spack.pkg
+        self._finder: Optional[RepoPath] = None
 
         # Maps that goes from package name to corresponding file stat
-        self._fast_package_checker = None
+        self._fast_package_checker: Optional[FastPackageChecker] = None
 
         # Indexes for this repository, computed lazily
-        self._repo_index = None
-        self._cache = cache or spack.caches.MISC_CACHE
+        self._repo_index: Optional[RepoIndex] = None
+        self._cache = cache
+
+    def finder(self, value: RepoPath) -> None:
+        self._finder = value
 
-    def real_name(self, import_name):
+    def real_name(self, import_name: str) -> Optional[str]:
         """Allow users to import Spack packages using Python identifiers.
 
         A python identifier might map to many different Spack package
@@ -999,18 +1041,21 @@ class Repo:
             return import_name
 
         options = nm.possible_spack_module_names(import_name)
-        options.remove(import_name)
+        try:
+            options.remove(import_name)
+        except ValueError:
+            pass
         for name in options:
             if name in self:
                 return name
         return None
 
-    def is_prefix(self, fullname):
+    def is_prefix(self, fullname: str) -> bool:
         """True if fullname is a prefix of this Repo's namespace."""
         parts = fullname.split(".")
         return self._names[: len(parts)] == parts
 
-    def _read_config(self):
+    def _read_config(self) -> Dict[str, str]:
         """Check for a YAML config file in this db's root directory."""
         try:
             with open(self.config_file) as reponame_file:
@@ -1021,14 +1066,14 @@ class Repo:
                     or "repo" not in yaml_data
                     or not isinstance(yaml_data["repo"], dict)
                 ):
-                    tty.die("Invalid %s in repository %s" % (repo_config_name, self.root))
+                    tty.die(f"Invalid {repo_config_name} in repository {self.root}")
 
                 return yaml_data["repo"]
 
         except IOError:
-            tty.die("Error reading %s when opening %s" % (self.config_file, self.root))
+            tty.die(f"Error reading {self.config_file} when opening {self.root}")
 
-    def get(self, spec):
+    def get(self, spec: "spack.spec.Spec") -> "spack.package_base.PackageBase":
         """Returns the package associated with the supplied spec."""
         msg = "Repo.get can only be called on concrete specs"
         assert isinstance(spec, spack.spec.Spec) and spec.concrete, msg
@@ -1049,16 +1094,13 @@ class Repo:
             # pass these through as their error messages will be fine.
             raise
         except Exception as e:
-            tty.debug(e)
-
             # Make sure other errors in constructors hit the error
             # handler by wrapping them
-            if spack.config.get("config:debug"):
-                sys.excepthook(*sys.exc_info())
-            raise FailedConstructorError(spec.fullname, *sys.exc_info())
+            tty.debug(e)
+            raise FailedConstructorError(spec.fullname, *sys.exc_info()) from e
 
     @autospec
-    def dump_provenance(self, spec, path):
+    def dump_provenance(self, spec: "spack.spec.Spec", path: str) -> None:
         """Dump provenance information for a spec to a particular path.
 
         This dumps the package file and any associated patch files.
@@ -1066,7 +1108,7 @@ class Repo:
         """
         if spec.namespace and spec.namespace != self.namespace:
             raise UnknownPackageError(
-                "Repository %s does not contain package %s." % (self.namespace, spec.fullname)
+                f"Repository {self.namespace} does not contain package {spec.fullname}."
             )
 
         package_path = self.filename_for_package_name(spec.name)
@@ -1083,17 +1125,13 @@ class Repo:
                     if os.path.exists(patch.path):
                         fs.install(patch.path, path)
                     else:
-                        tty.warn("Patch file did not exist: %s" % patch.path)
+                        warnings.warn(f"Patch file did not exist: {patch.path}")
 
         # Install the package.py file itself.
         fs.install(self.filename_for_package_name(spec.name), path)
 
-    def purge(self):
-        """Clear entire package instance cache."""
-        self._instances.clear()
-
     @property
-    def index(self):
+    def index(self) -> RepoIndex:
         """Construct the index for this repo lazily."""
         if self._repo_index is None:
             self._repo_index = RepoIndex(self._pkg_checker, self.namespace, cache=self._cache)
@@ -1103,42 +1141,40 @@ class Repo:
         return self._repo_index
 
     @property
-    def provider_index(self):
+    def provider_index(self) -> spack.provider_index.ProviderIndex:
         """A provider index with names *specific* to this repo."""
         return self.index["providers"]
 
     @property
-    def tag_index(self):
+    def tag_index(self) -> spack.tag.TagIndex:
         """Index of tags and which packages they're defined on."""
         return self.index["tags"]
 
     @property
-    def patch_index(self):
+    def patch_index(self) -> spack.patch.PatchCache:
         """Index of patches and packages they're defined on."""
         return self.index["patches"]
 
     @autospec
-    def providers_for(self, vpkg_spec):
+    def providers_for(self, vpkg_spec: "spack.spec.Spec") -> List["spack.spec.Spec"]:
         providers = self.provider_index.providers_for(vpkg_spec)
         if not providers:
             raise UnknownPackageError(vpkg_spec.fullname)
         return providers
 
     @autospec
-    def extensions_for(self, extendee_spec):
-        return [
-            pkg_cls(spack.spec.Spec(pkg_cls.name))
-            for pkg_cls in self.all_package_classes()
-            if pkg_cls(spack.spec.Spec(pkg_cls.name)).extends(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."""
+    def extensions_for(
+        self, extendee_spec: "spack.spec.Spec"
+    ) -> List["spack.package_base.PackageBase"]:
+        result = [pkg_cls(spack.spec.Spec(pkg_cls.name)) for pkg_cls in self.all_package_classes()]
+        return [x for x in result if x.extends(extendee_spec)]
+
+    def dirname_for_package_name(self, pkg_name: str) -> str:
+        """Given a package name, get the directory containing its package.py file."""
         _, unqualified_name = self.partition_package_name(pkg_name)
         return os.path.join(self.packages_path, unqualified_name)
 
-    def filename_for_package_name(self, pkg_name):
+    def filename_for_package_name(self, pkg_name: str) -> str:
         """Get the filename for the module we should load for a particular
         package.  Packages for a Repo live in
         ``$root/<package_name>/package.py``
@@ -1151,23 +1187,23 @@ class Repo:
         return os.path.join(pkg_dir, package_file_name)
 
     @property
-    def _pkg_checker(self):
+    def _pkg_checker(self) -> FastPackageChecker:
         if self._fast_package_checker is None:
             self._fast_package_checker = FastPackageChecker(self.packages_path)
         return self._fast_package_checker
 
-    def all_package_names(self, include_virtuals=False):
+    def all_package_names(self, include_virtuals: bool = False) -> List[str]:
         """Returns a sorted list of all package names in the Repo."""
         names = sorted(self._pkg_checker.keys())
         if include_virtuals:
             return names
         return [x for x in names if not self.is_virtual(x)]
 
-    def package_path(self, name):
+    def package_path(self, name: str) -> str:
         """Get path to package.py file for this repo."""
         return os.path.join(self.packages_path, name, package_file_name)
 
-    def all_package_paths(self):
+    def all_package_paths(self) -> Generator[str, None, None]:
         for name in self.all_package_names():
             yield self.package_path(name)
 
@@ -1176,7 +1212,7 @@ class Repo:
         v.intersection_update(*(self.tag_index[tag.lower()] for tag in tags))
         return v
 
-    def all_package_classes(self):
+    def all_package_classes(self) -> Generator[Type["spack.package_base.PackageBase"], None, None]:
         """Iterator over all package *classes* in the repository.
 
         Use this with care, because loading packages is slow.
@@ -1184,7 +1220,7 @@ class Repo:
         for name in self.all_package_names():
             yield self.get_pkg_class(name)
 
-    def exists(self, pkg_name):
+    def exists(self, pkg_name: str) -> bool:
         """Whether a package with the supplied name exists."""
         if pkg_name is None:
             return False
@@ -1201,28 +1237,22 @@ class Repo:
         """Time a package file in this repo was last updated."""
         return self._pkg_checker.last_mtime()
 
-    def is_virtual(self, pkg_name):
+    def is_virtual(self, pkg_name: str) -> bool:
         """Return True if the package with this name is virtual, False otherwise.
 
         This function use the provider index. If calling from a code block that
         is used to construct the provider index use the ``is_virtual_safe`` function.
-
-        Args:
-            pkg_name (str): name of the package we want to check
         """
         return pkg_name in self.provider_index
 
-    def is_virtual_safe(self, pkg_name):
+    def is_virtual_safe(self, pkg_name: str) -> bool:
         """Return True if the package with this name is virtual, False otherwise.
 
         This function doesn't use the provider index.
-
-        Args:
-            pkg_name (str): name of the package we want to check
         """
         return not self.exists(pkg_name) or self.get_pkg_class(pkg_name).virtual
 
-    def get_pkg_class(self, pkg_name):
+    def get_pkg_class(self, pkg_name: str) -> Type["spack.package_base.PackageBase"]:
         """Get the class for the package out of its module.
 
         First loads (or fetches from cache) a module for the
@@ -1234,7 +1264,8 @@ class Repo:
         fullname = f"{self.full_namespace}.{pkg_name}"
 
         try:
-            module = importlib.import_module(fullname)
+            with REPOS_FINDER.switch_repo(self._finder or self):
+                module = importlib.import_module(fullname)
         except ImportError:
             raise UnknownPackageError(fullname)
         except Exception as e:
@@ -1245,26 +1276,21 @@ class Repo:
         if not inspect.isclass(cls):
             tty.die(f"{pkg_name}.{class_name} is not a class")
 
-        new_cfg_settings = (
-            spack.config.get("packages").get(pkg_name, {}).get("package_attributes", {})
-        )
-
+        # Clear any prior changes to class attributes in case the class was loaded from the
+        # same repo, but with different overrides
         overridden_attrs = getattr(cls, "overridden_attrs", {})
         attrs_exclusively_from_config = getattr(cls, "attrs_exclusively_from_config", [])
-        # Clear any prior changes to class attributes in case the config has
-        # since changed
         for key, val in overridden_attrs.items():
             setattr(cls, key, val)
         for key in attrs_exclusively_from_config:
             delattr(cls, key)
 
-        # Keep track of every class attribute that is overridden by the config:
-        # if the config changes between calls to this method, we make sure to
-        # restore the original config values (in case the new config no longer
-        # sets attributes that it used to)
+        # Keep track of every class attribute that is overridden: if different overrides
+        # dictionaries are used on the same physical repo, we make sure to restore the original
+        # config values
         new_overridden_attrs = {}
         new_attrs_exclusively_from_config = set()
-        for key, val in new_cfg_settings.items():
+        for key, val in self.overrides.get(pkg_name, {}).items():
             if hasattr(cls, key):
                 new_overridden_attrs[key] = getattr(cls, key)
             else:
@@ -1291,13 +1317,13 @@ class Repo:
 
         return namespace, pkg_name
 
-    def __str__(self):
-        return "[Repo '%s' at '%s']" % (self.namespace, self.root)
+    def __str__(self) -> str:
+        return f"Repo '{self.namespace}' at {self.root}"
 
-    def __repr__(self):
+    def __repr__(self) -> str:
         return self.__str__()
 
-    def __contains__(self, pkg_name):
+    def __contains__(self, pkg_name: str) -> bool:
         return self.exists(pkg_name)
 
 
@@ -1373,12 +1399,17 @@ def create_repo(root, namespace=None, subdir=packages_dir_name):
     return full_path, namespace
 
 
+def from_path(path: str) -> "Repo":
+    """Returns a repository from the path passed as input. Injects the global misc cache."""
+    return Repo(path, cache=spack.caches.MISC_CACHE)
+
+
 def create_or_construct(path, namespace=None):
     """Create a repository, or just return a Repo if it already exists."""
     if not os.path.exists(path):
         fs.mkdirp(path)
         create_repo(path, namespace)
-    return Repo(path)
+    return from_path(path)
 
 
 def _path(configuration=None):
@@ -1396,7 +1427,17 @@ def create(configuration):
     repo_dirs = configuration.get("repos")
     if not repo_dirs:
         raise NoRepoConfiguredError("Spack configuration contains no package repositories.")
-    return RepoPath(*repo_dirs)
+
+    overrides = {}
+    for pkg_name, data in configuration.get("packages").items():
+        if pkg_name == "all":
+            continue
+        value = data.get("package_attributes", {})
+        if not value:
+            continue
+        overrides[pkg_name] = value
+
+    return RepoPath(*repo_dirs, cache=spack.caches.MISC_CACHE, overrides=overrides)
 
 
 #: Singleton repo path instance
diff --git a/lib/spack/spack/test/cmd/pkg.py b/lib/spack/spack/test/cmd/pkg.py
index f37d66363e..ecf30f0518 100644
--- a/lib/spack/spack/test/cmd/pkg.py
+++ b/lib/spack/spack/test/cmd/pkg.py
@@ -13,6 +13,7 @@ from llnl.util.filesystem import mkdirp, working_dir
 import spack.cmd.pkg
 import spack.main
 import spack.repo
+import spack.util.file_cache
 
 #: new fake package template
 pkg_template = """\
@@ -34,13 +35,14 @@ abd = set(("pkg-a", "pkg-b", "pkg-d"))
 
 # Force all tests to use a git repository *in* the mock packages repo.
 @pytest.fixture(scope="module")
-def mock_pkg_git_repo(git, tmpdir_factory):
+def mock_pkg_git_repo(git, tmp_path_factory):
     """Copy the builtin.mock repo and make a mutable git repo inside it."""
-    tmproot = tmpdir_factory.mktemp("mock_pkg_git_repo")
-    repo_path = tmproot.join("builtin.mock")
+    root_dir = tmp_path_factory.mktemp("mock_pkg_git_repo")
+    repo_dir = root_dir / "builtin.mock"
+    shutil.copytree(spack.paths.mock_packages_path, str(repo_dir))
 
-    shutil.copytree(spack.paths.mock_packages_path, str(repo_path))
-    mock_repo = spack.repo.RepoPath(str(repo_path))
+    repo_cache = spack.util.file_cache.FileCache(str(root_dir / "cache"))
+    mock_repo = spack.repo.RepoPath(str(repo_dir), cache=repo_cache)
     mock_repo_packages = mock_repo.repos[0].packages_path
 
     with working_dir(mock_repo_packages):
@@ -75,7 +77,7 @@ def mock_pkg_git_repo(git, tmpdir_factory):
         git("rm", "-rf", "pkg-c")
         git("-c", "commit.gpgsign=false", "commit", "-m", "change pkg-b, remove pkg-c, add pkg-d")
 
-    with spack.repo.use_repositories(str(repo_path)):
+    with spack.repo.use_repositories(str(repo_dir)):
         yield mock_repo_packages
 
 
diff --git a/lib/spack/spack/test/cmd/style.py b/lib/spack/spack/test/cmd/style.py
index afdb3dbb1f..5605181604 100644
--- a/lib/spack/spack/test/cmd/style.py
+++ b/lib/spack/spack/test/cmd/style.py
@@ -38,7 +38,7 @@ def flake8_package(tmpdir):
     change to the ``flake8`` mock package, yields the filename, then undoes the
     change on cleanup.
     """
-    repo = spack.repo.Repo(spack.paths.mock_packages_path)
+    repo = spack.repo.from_path(spack.paths.mock_packages_path)
     filename = repo.filename_for_package_name("flake8")
     rel_path = os.path.dirname(os.path.relpath(filename, spack.paths.prefix))
     tmp = tmpdir / rel_path / "flake8-ci-package.py"
@@ -54,7 +54,7 @@ def flake8_package(tmpdir):
 @pytest.fixture
 def flake8_package_with_errors(scope="function"):
     """A flake8 package with errors."""
-    repo = spack.repo.Repo(spack.paths.mock_packages_path)
+    repo = spack.repo.from_path(spack.paths.mock_packages_path)
     filename = repo.filename_for_package_name("flake8")
     tmp = filename + ".tmp"
 
@@ -130,7 +130,7 @@ def test_changed_files_all_files():
     assert os.path.join(spack.paths.module_path, "spec.py") in files
 
     # a mock package
-    repo = spack.repo.Repo(spack.paths.mock_packages_path)
+    repo = spack.repo.from_path(spack.paths.mock_packages_path)
     filename = repo.filename_for_package_name("flake8")
     assert filename in files
 
diff --git a/lib/spack/spack/test/concretize.py b/lib/spack/spack/test/concretize.py
index 9a80f361a1..c69f680dd1 100644
--- a/lib/spack/spack/test/concretize.py
+++ b/lib/spack/spack/test/concretize.py
@@ -24,6 +24,7 @@ import spack.hash_types as ht
 import spack.platforms
 import spack.repo
 import spack.solver.asp
+import spack.util.file_cache
 import spack.util.libc
 import spack.variant as vt
 from spack.concretize import find_spec
@@ -168,19 +169,18 @@ def fuzz_dep_order(request, monkeypatch):
 
 
 @pytest.fixture()
-def repo_with_changing_recipe(tmpdir_factory, mutable_mock_repo):
+def repo_with_changing_recipe(tmp_path_factory, mutable_mock_repo):
     repo_namespace = "changing"
-    repo_dir = tmpdir_factory.mktemp(repo_namespace)
+    repo_dir = tmp_path_factory.mktemp(repo_namespace)
 
-    repo_dir.join("repo.yaml").write(
+    (repo_dir / "repo.yaml").write_text(
         """
 repo:
   namespace: changing
-""",
-        ensure=True,
+"""
     )
 
-    packages_dir = repo_dir.ensure("packages", dir=True)
+    packages_dir = repo_dir / "packages"
     root_pkg_str = """
 class Root(Package):
     homepage = "http://www.example.com"
@@ -191,7 +191,9 @@ class Root(Package):
 
     conflicts("^changing~foo")
 """
-    packages_dir.join("root", "package.py").write(root_pkg_str, ensure=True)
+    package_py = packages_dir / "root" / "package.py"
+    package_py.parent.mkdir(parents=True)
+    package_py.write_text(root_pkg_str)
 
     changing_template = """
 class Changing(Package):
@@ -225,7 +227,9 @@ class Changing(Package):
 
             def __init__(self, repo_directory):
                 self.repo_dir = repo_directory
-                self.repo = spack.repo.Repo(str(repo_directory))
+                cache_dir = tmp_path_factory.mktemp("cache")
+                self.repo_cache = spack.util.file_cache.FileCache(str(cache_dir))
+                self.repo = spack.repo.Repo(str(repo_directory), cache=self.repo_cache)
 
             def change(self, changes=None):
                 changes = changes or {}
@@ -246,10 +250,12 @@ class Changing(Package):
                 # Change the recipe
                 t = jinja2.Template(changing_template)
                 changing_pkg_str = t.render(**context)
-                packages_dir.join("changing", "package.py").write(changing_pkg_str, ensure=True)
+                package_py = packages_dir / "changing" / "package.py"
+                package_py.parent.mkdir(parents=True, exist_ok=True)
+                package_py.write_text(changing_pkg_str)
 
                 # Re-add the repository
-                self.repo = spack.repo.Repo(str(self.repo_dir))
+                self.repo = spack.repo.Repo(str(self.repo_dir), cache=self.repo_cache)
                 repository.put_first(self.repo)
 
         _changing_pkg = _ChangingPackage(repo_dir)
diff --git a/lib/spack/spack/test/concretize_preferences.py b/lib/spack/spack/test/concretize_preferences.py
index a7683bf65f..6748b845aa 100644
--- a/lib/spack/spack/test/concretize_preferences.py
+++ b/lib/spack/spack/test/concretize_preferences.py
@@ -161,21 +161,24 @@ class TestConcretizePreferences:
         spec = concretize("mpileaks")
         assert "zmpi" in spec
 
-    def test_config_set_pkg_property_url(self, mutable_mock_repo):
+    @pytest.mark.parametrize(
+        "update,expected",
+        [
+            (
+                {"url": "http://www.somewhereelse.com/mpileaks-1.0.tar.gz"},
+                "http://www.somewhereelse.com/mpileaks-2.3.tar.gz",
+            ),
+            ({}, "http://www.llnl.gov/mpileaks-2.3.tar.gz"),
+        ],
+    )
+    def test_config_set_pkg_property_url(self, update, expected, mock_repo_path):
         """Test setting an existing attribute in the package class"""
-        update_packages(
-            "mpileaks",
-            "package_attributes",
-            {"url": "http://www.somewhereelse.com/mpileaks-1.0.tar.gz"},
-        )
-        spec = concretize("mpileaks")
-        assert spec.package.fetcher.url == "http://www.somewhereelse.com/mpileaks-2.3.tar.gz"
-
-        update_packages("mpileaks", "package_attributes", {})
-        spec = concretize("mpileaks")
-        assert spec.package.fetcher.url == "http://www.llnl.gov/mpileaks-2.3.tar.gz"
+        update_packages("mpileaks", "package_attributes", update)
+        with spack.repo.use_repositories(mock_repo_path):
+            spec = concretize("mpileaks")
+            assert spec.package.fetcher.url == expected
 
-    def test_config_set_pkg_property_new(self, mutable_mock_repo):
+    def test_config_set_pkg_property_new(self, mock_repo_path):
         """Test that you can set arbitrary attributes on the Package class"""
         conf = syaml.load_config(
             """\
@@ -194,19 +197,20 @@ mpileaks:
 """
         )
         spack.config.set("packages", conf, scope="concretize")
-
-        spec = concretize("mpileaks")
-        assert spec.package.v1 == 1
-        assert spec.package.v2 is True
-        assert spec.package.v3 == "yesterday"
-        assert spec.package.v4 == "true"
-        assert dict(spec.package.v5) == {"x": 1, "y": 2}
-        assert list(spec.package.v6) == [1, 2]
+        with spack.repo.use_repositories(mock_repo_path):
+            spec = concretize("mpileaks")
+            assert spec.package.v1 == 1
+            assert spec.package.v2 is True
+            assert spec.package.v3 == "yesterday"
+            assert spec.package.v4 == "true"
+            assert dict(spec.package.v5) == {"x": 1, "y": 2}
+            assert list(spec.package.v6) == [1, 2]
 
         update_packages("mpileaks", "package_attributes", {})
-        spec = concretize("mpileaks")
-        with pytest.raises(AttributeError):
-            spec.package.v1
+        with spack.repo.use_repositories(mock_repo_path):
+            spec = concretize("mpileaks")
+            with pytest.raises(AttributeError):
+                spec.package.v1
 
     def test_preferred(self):
         """ "Test packages with some version marked as preferred=True"""
diff --git a/lib/spack/spack/test/conftest.py b/lib/spack/spack/test/conftest.py
index 7a6bd0622f..94d0969d0c 100644
--- a/lib/spack/spack/test/conftest.py
+++ b/lib/spack/spack/test/conftest.py
@@ -561,7 +561,7 @@ def _use_test_platform(test_platform):
 #
 @pytest.fixture(scope="session")
 def mock_repo_path():
-    yield spack.repo.Repo(spack.paths.mock_packages_path)
+    yield spack.repo.from_path(spack.paths.mock_packages_path)
 
 
 def _pkg_install_fn(pkg, spec, prefix):
@@ -588,7 +588,7 @@ def mock_packages(mock_repo_path, mock_pkg_install, request):
 def mutable_mock_repo(mock_repo_path, request):
     """Function-scoped mock packages, for tests that need to modify them."""
     ensure_configuration_fixture_run_before(request)
-    mock_repo = spack.repo.Repo(spack.paths.mock_packages_path)
+    mock_repo = spack.repo.from_path(spack.paths.mock_packages_path)
     with spack.repo.use_repositories(mock_repo) as mock_repo_path:
         yield mock_repo_path
 
@@ -2019,7 +2019,8 @@ repo:
         with open(str(pkg_file), "w") as f:
             f.write(pkg_str)
 
-    return spack.repo.Repo(repo_path)
+    repo_cache = spack.util.file_cache.FileCache(str(tmpdir.join("cache")))
+    return spack.repo.Repo(repo_path, cache=repo_cache)
 
 
 @pytest.fixture()
@@ -2061,3 +2062,9 @@ def _c_compiler_always_exists():
     spack.solver.asp.c_compiler_runs = _true
     yield
     spack.solver.asp.c_compiler_runs = fn
+
+
+@pytest.fixture(scope="session")
+def mock_test_cache(tmp_path_factory):
+    cache_dir = tmp_path_factory.mktemp("cache")
+    return spack.util.file_cache.FileCache(str(cache_dir))
diff --git a/lib/spack/spack/test/directory_layout.py b/lib/spack/spack/test/directory_layout.py
index 6f42281827..da51de415e 100644
--- a/lib/spack/spack/test/directory_layout.py
+++ b/lib/spack/spack/test/directory_layout.py
@@ -146,7 +146,7 @@ def test_read_and_write_spec(temporary_store, config, mock_packages):
         assert not os.path.exists(install_dir)
 
 
-def test_handle_unknown_package(temporary_store, config, mock_packages):
+def test_handle_unknown_package(temporary_store, config, mock_packages, tmp_path):
     """This test ensures that spack can at least do *some*
     operations with packages that are installed but that it
     does not know about.  This is actually not such an uncommon
@@ -158,7 +158,9 @@ def test_handle_unknown_package(temporary_store, config, mock_packages):
     or query them again if the package goes away.
     """
     layout = temporary_store.layout
-    mock_db = spack.repo.RepoPath(spack.paths.mock_packages_path)
+
+    repo_cache = spack.util.file_cache.FileCache(str(tmp_path / "cache"))
+    mock_db = spack.repo.RepoPath(spack.paths.mock_packages_path, cache=repo_cache)
 
     not_in_mock = set.difference(
         set(spack.repo.all_package_names()), set(mock_db.all_package_names())
diff --git a/lib/spack/spack/test/packages.py b/lib/spack/spack/test/packages.py
index f2507ee57e..d00db3ed0c 100644
--- a/lib/spack/spack/test/packages.py
+++ b/lib/spack/spack/test/packages.py
@@ -32,12 +32,12 @@ class TestPackage:
         assert pkg_cls.name == "mpich"
 
     def test_package_filename(self):
-        repo = spack.repo.Repo(mock_packages_path)
+        repo = spack.repo.from_path(mock_packages_path)
         filename = repo.filename_for_package_name("mpich")
         assert filename == os.path.join(mock_packages_path, "packages", "mpich", "package.py")
 
     def test_nonexisting_package_filename(self):
-        repo = spack.repo.Repo(mock_packages_path)
+        repo = spack.repo.from_path(mock_packages_path)
         filename = repo.filename_for_package_name("some-nonexisting-package")
         assert filename == os.path.join(
             mock_packages_path, "packages", "some-nonexisting-package", "package.py"
diff --git a/lib/spack/spack/test/repo.py b/lib/spack/spack/test/repo.py
index 877b4af243..3aa9f00698 100644
--- a/lib/spack/spack/test/repo.py
+++ b/lib/spack/spack/test/repo.py
@@ -12,21 +12,28 @@ import spack.repo
 
 
 @pytest.fixture(params=["packages", "", "foo"])
-def extra_repo(tmpdir_factory, request):
+def extra_repo(tmp_path_factory, request):
     repo_namespace = "extra_test_repo"
-    repo_dir = tmpdir_factory.mktemp(repo_namespace)
-    repo_dir.ensure(request.param, dir=True)
-
-    with open(str(repo_dir.join("repo.yaml")), "w") as f:
-        f.write(
+    repo_dir = tmp_path_factory.mktemp(repo_namespace)
+    cache_dir = tmp_path_factory.mktemp("cache")
+    (repo_dir / request.param).mkdir(parents=True, exist_ok=True)
+    if request.param == "packages":
+        (repo_dir / "repo.yaml").write_text(
             """
 repo:
   namespace: extra_test_repo
 """
         )
-        if request.param != "packages":
-            f.write(f"  subdirectory: '{request.param}'")
-    return (spack.repo.Repo(str(repo_dir)), request.param)
+    else:
+        (repo_dir / "repo.yaml").write_text(
+            f"""
+repo:
+  namespace: extra_test_repo
+  subdirectory: '{request.param}'
+"""
+        )
+    repo_cache = spack.util.file_cache.FileCache(str(cache_dir))
+    return spack.repo.Repo(str(repo_dir), cache=repo_cache), request.param
 
 
 def test_repo_getpkg(mutable_mock_repo):
@@ -177,8 +184,11 @@ def test_repo_dump_virtuals(tmpdir, mutable_mock_repo, mock_packages, ensure_deb
         ([spack.paths.mock_packages_path, spack.paths.packages_path], ["builtin.mock", "builtin"]),
     ],
 )
-def test_repository_construction_doesnt_use_globals(nullify_globals, repo_paths, namespaces):
-    repo_path = spack.repo.RepoPath(*repo_paths)
+def test_repository_construction_doesnt_use_globals(
+    nullify_globals, tmp_path, repo_paths, namespaces
+):
+    repo_cache = spack.util.file_cache.FileCache(str(tmp_path / "cache"))
+    repo_path = spack.repo.RepoPath(*repo_paths, cache=repo_cache)
     assert len(repo_path.repos) == len(namespaces)
     assert [x.namespace for x in repo_path.repos] == namespaces
 
@@ -188,8 +198,84 @@ 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)
+    repo_path = spack.repo.RepoPath(mock_repo_path, cache=None)
     method = getattr(repo_path, method_name)
     unqualified = method("mpileaks")
     qualified = method("builtin.mock.mpileaks")
     assert qualified == unqualified
+
+
+@pytest.mark.usefixtures("nullify_globals")
+class TestRepo:
+    """Test that the Repo class work correctly, and does not depend on globals,
+    except the REPOS_FINDER.
+    """
+
+    def test_creation(self, mock_test_cache):
+        repo = spack.repo.Repo(spack.paths.mock_packages_path, cache=mock_test_cache)
+        assert repo.config_file.endswith("repo.yaml")
+        assert repo.namespace == "builtin.mock"
+
+    @pytest.mark.parametrize(
+        "name,expected", [("mpi", True), ("mpich", False), ("mpileaks", False)]
+    )
+    def test_is_virtual(self, name, expected, mock_test_cache):
+        repo = spack.repo.Repo(spack.paths.mock_packages_path, cache=mock_test_cache)
+        assert repo.is_virtual(name) is expected
+        assert repo.is_virtual_safe(name) is expected
+
+    @pytest.mark.parametrize(
+        "module_name,expected",
+        [
+            ("dla_future", "dla-future"),
+            ("num7zip", "7zip"),
+            # If no package is there, None is returned
+            ("unknown", None),
+        ],
+    )
+    def test_real_name(self, module_name, expected, mock_test_cache):
+        """Test that we can correctly compute the 'real' name of a package, from the one
+        used to import the Python module.
+        """
+        repo = spack.repo.Repo(spack.paths.mock_packages_path, cache=mock_test_cache)
+        assert repo.real_name(module_name) == expected
+
+    @pytest.mark.parametrize("name", ["mpileaks", "7zip", "dla-future"])
+    def test_get(self, name, mock_test_cache):
+        repo = spack.repo.Repo(spack.paths.mock_packages_path, cache=mock_test_cache)
+        mock_spec = spack.spec.Spec(name)
+        mock_spec._mark_concrete()
+        pkg = repo.get(mock_spec)
+        assert pkg.__class__ == repo.get_pkg_class(name)
+
+    @pytest.mark.parametrize("virtual_name,expected", [("mpi", ["mpich", "zmpi"])])
+    def test_providers(self, virtual_name, expected, mock_test_cache):
+        repo = spack.repo.Repo(spack.paths.mock_packages_path, cache=mock_test_cache)
+        provider_names = {x.name for x in repo.providers_for(virtual_name)}
+        assert provider_names.issuperset(expected)
+
+    @pytest.mark.parametrize(
+        "extended,expected",
+        [("python", ["py-extension1", "python-venv"]), ("perl", ["perl-extension"])],
+    )
+    def test_extensions(self, extended, expected, mock_test_cache):
+        repo = spack.repo.Repo(spack.paths.mock_packages_path, cache=mock_test_cache)
+        provider_names = {x.name for x in repo.extensions_for(extended)}
+        assert provider_names.issuperset(expected)
+
+    def test_all_package_names(self, mock_test_cache):
+        repo = spack.repo.Repo(spack.paths.mock_packages_path, cache=mock_test_cache)
+        all_names = repo.all_package_names(include_virtuals=True)
+        real_names = repo.all_package_names(include_virtuals=False)
+        assert set(all_names).issuperset(real_names)
+        for name in set(all_names) - set(real_names):
+            assert repo.is_virtual(name)
+            assert repo.is_virtual_safe(name)
+
+    def test_packages_with_tags(self, mock_test_cache):
+        repo = spack.repo.Repo(spack.paths.mock_packages_path, cache=mock_test_cache)
+        r1 = repo.packages_with_tags("tag1")
+        r2 = repo.packages_with_tags("tag1", "tag2")
+        assert "mpich" in r1 and "mpich" in r2
+        assert "mpich2" in r1 and "mpich2" not in r2
+        assert set(r2).issubset(r1)