importlib: Read distribution name/version from metadata directory name, 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.

.egg-info directory names tend to not include the version so they are
not considered for optimizing version lookup.

simplewheel-2.0-1-py2.py3-none-any.whl had to be modified to rename the
.dist-info directory which mistakenly included the wheel build tag (in
violation of the wheel specification).

    simplewheel/__init__.py
    simplewheel-2.0-1.dist-info/DESCRIPTION.rst
    simplewheel-2.0-1.dist-info/metadata.json
    simplewheel-2.0-1.dist-info/top_level.txt
    simplewheel-2.0-1.dist-info/WHEEL
    simplewheel-2.0-1.dist-info/METADATA
    simplewheel-2.0-1.dist-info/RECORD

Otherwise, it was mistaken for part of the version and led pip to think
the wheel was a post-release, breaking tests...

Author: ichard26

news/aa82171b-1578-4128-8db3-9aa72b3a6a84.trivial.rst

@@ -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/_compat.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 == ".dist-info":
+                version = stem.split("-", 1)[1]
+                return parse_version(version)
+
         return parse_version(self._dist.version)
 
     def is_file(self, path: InfoPath) -> bool:

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

@@ -1172,7 +1172,7 @@ def test_install_nonlocal_compatible_wheel(
     )
     assert result.returncode == SUCCESS
 
-    distinfo = Path("scratch") / "target" / "simplewheel-2.0-1.dist-info"
+    distinfo = Path("scratch") / "target" / "simplewheel-2.0.dist-info"
     result.did_create(distinfo)
 
     # Test install without --target

tests/data/packages/simplewheel-2.0-1-py2.py3-none-any.whl

@@ -39,7 +39,7 @@ def test_install_report_basic(
     assert url.endswith("/packages/simplewheel-2.0-1-py2.py3-none-any.whl")
     assert (
         simplewheel_report["download_info"]["archive_info"]["hash"]
-        == "sha256=191d6520d0570b13580bf7642c97ddfbb46dd04da5dd2cf7bef9f32391dfe716"
+        == "sha256=71e1ca6b16ae3382a698c284013f66504f2581099b2ce4801f60e9536236ceee"
     )