importlib: Read distribution name/version from metadata directory nam…

…e, if possible

importlib does not cache metadata in-memory, so querying even simple
attributes like distribution names and versions can quickly become
expensive (as each access requires reading METADATA). Fortunately,
`Distribution.canonical_name` is optimized to parse the metadata
directory name to query the name if possible. This commit extends this
optimization to the finder implementation and version attribute.

src/pip/_internal/metadata/importlib/_compat.py

@@ -1,4 +1,5 @@
 import importlib.metadata
+import os
 from typing import Any, Optional, Protocol, cast
 
 
@@ -49,6 +50,13 @@ def get_dist_name(dist: importlib.metadata.Distribution) -> str:
     The ``name`` attribute is only available in Python 3.10 or later. We are
     targeting exactly that, but Mypy does not know this.
     """
+    # Try to get the name from the metadata directory name.
+    # This is much faster than reading metadata.
+    if info_location := get_info_location(dist):
+        stem, suffix = os.path.splitext(info_location.name)
+        if suffix in (".dist-info", ".egg-info"):
+            return stem.split("-", 1)[0]
+
     name = cast(Any, dist).name
     if not isinstance(name, str):
         raise BadMetadata(dist, reason="invalid metadata entry 'name'")

src/pip/_internal/metadata/importlib/_dists.py

@@ -153,25 +153,20 @@ def installed_location(self) -> Optional[str]:
             return None
         return normalize_path(str(self._installed_location))
 
-    def _get_dist_name_from_location(self) -> Optional[str]:
-        """Try to get the name from the metadata directory name.
-
-        This is much faster than reading metadata.
-        """
-        if self._info_location is None:
-            return None
-        stem, suffix = os.path.splitext(self._info_location.name)
-        if suffix not in (".dist-info", ".egg-info"):
-            return None
-        return stem.split("-", 1)[0]
-
     @property
     def canonical_name(self) -> NormalizedName:
-        name = self._get_dist_name_from_location() or get_dist_name(self._dist)
-        return canonicalize_name(name)
+        return canonicalize_name(get_dist_name(self._dist))
 
     @property
     def version(self) -> DistributionVersion:
+        # Try to get the version from the metadata directory name.
+        # This is much faster than reading metadata.
+        if self._info_location is not None:
+            stem, suffix = os.path.splitext(self._info_location.name)
+            if suffix in (".dist-info", ".egg-info"):
+                version = stem.split("-", 1)[1]
+                return parse_version(version)
+
         return parse_version(self._dist.version)
 
     def is_file(self, path: InfoPath) -> bool: