Parse pkg_resources Dist versions with packaging.version

Due to a mix of bundled and unbundled dependencies, pkg_resources
Version class may not be the same as packaging's Version class.

See: pypa/setuptools#2052

src/pip/_internal/metadata/pkg_resources.py

@@ -3,7 +3,7 @@
 
 from pip._vendor import pkg_resources
 from pip._vendor.packaging.utils import canonicalize_name
-from pip._vendor.packaging.version import _BaseVersion
+from pip._vendor.packaging.version import _BaseVersion, parse as parse_version
 
 from pip._internal.utils import misc  # TODO: Move definition here.
 from pip._internal.utils.packaging import get_installer
@@ -16,6 +16,7 @@ class Distribution(BaseDistribution):
     def __init__(self, dist):
         # type: (pkg_resources.Distribution) -> None
         self._dist = dist
+        self._version = None
 
     @classmethod
     def from_wheel(cls, path, name):
@@ -45,7 +46,9 @@ def canonical_name(self):
     @property
     def version(self):
         # type: () -> _BaseVersion
-        return self._dist.parsed_version
+        if self._version is None:
+            self._version = parse_version(self._dist.version)
+        return self._version
 
     @property
     def installer(self):

src/pip/_internal/resolution/resolvelib/candidates.py

@@ -5,6 +5,7 @@
 from pip._vendor.packaging.specifiers import InvalidSpecifier, SpecifierSet
 from pip._vendor.packaging.utils import canonicalize_name
 from pip._vendor.packaging.version import Version, _BaseVersion
+from pip._vendor.packaging.version import parse as parse_version
 from pip._vendor.pkg_resources import Distribution
 
 from pip._internal.exceptions import HashError, MetadataInconsistent
@@ -180,7 +181,7 @@ def name(self):
     def version(self):
         # type: () -> _BaseVersion
         if self._version is None:
-            self._version = self.dist.parsed_version
+            self._version = parse_version(self.dist.version)
         return self._version
 
     def format_for_error(self):
@@ -206,7 +207,8 @@ def _check_metadata_consistency(self, dist):
                 self._name,
                 dist.project_name,
             )
-        if self._version is not None and self._version != dist.parsed_version:
+        parsed_version = parse_version(dist.version)
+        if self._version is not None and self._version != parsed_version:
             raise MetadataInconsistent(
                 self._ireq,
                 "version",
@@ -345,6 +347,7 @@ def __init__(
         self.dist = dist
         self._ireq = make_install_req_from_dist(dist, template)
         self._factory = factory
+        self._version = None
 
         # This is just logging some messages, so we can do it eagerly.
         # The returned dist would be exactly the same as self.dist because we
@@ -387,7 +390,9 @@ def name(self):
     @property
     def version(self):
         # type: () -> _BaseVersion
-        return self.dist.parsed_version
+        if self._version is None:
+            self._version = parse_version(self.dist.version)
+        return self._version
 
     @property
     def is_editable(self):

src/pip/_internal/resolution/resolvelib/resolver.py

@@ -4,6 +4,7 @@
 from typing import TYPE_CHECKING, Dict, List, Optional, Set, Tuple
 
 from pip._vendor.packaging.utils import canonicalize_name
+from pip._vendor.packaging.version import parse as parse_version
 from pip._vendor.resolvelib import ResolutionImpossible
 from pip._vendor.resolvelib import Resolver as RLResolver
 from pip._vendor.resolvelib.resolvers import Result
@@ -139,7 +140,7 @@ def resolve(self, root_reqs, check_supported_wheels):
             elif self.factory.force_reinstall:
                 # The --force-reinstall flag is set -- reinstall.
                 ireq.should_reinstall = True
-            elif installed_dist.parsed_version != candidate.version:
+            elif parse_version(installed_dist.version) != candidate.version:
                 # The installation is different in version -- reinstall.
                 ireq.should_reinstall = True
             elif candidate.is_editable or dist_is_editable(installed_dist):