Don't consider dist-info in a wheel as "installed"

This applies to the new importlib.metadata backend. The legacy
pkg_resources backend already does this (albeit accidentally).

A package inside a wheel is not guaranteed to "work" when directly
imported, so we should not treat it as an installed distribution.

news/11217.bugfix.rst

@@ -0,0 +1,4 @@
+Do not consider a ``.dist-info`` directory found inside a wheel-like zip file
+as metadata for an installed distribution. A package in a wheel is (by
+definition) not installed, and is not guaranteed to work due to how a wheel is
+structured.

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

@@ -10,12 +10,24 @@
 from pip._vendor.packaging.utils import NormalizedName, canonicalize_name
 
 from pip._internal.metadata.base import BaseDistribution, BaseEnvironment
+from pip._internal.models.wheel import Wheel
 from pip._internal.utils.deprecation import deprecated
+from pip._internal.utils.filetypes import WHEEL_EXTENSION
 
 from ._compat import BasePath, get_dist_name, get_info_location
 from ._dists import Distribution
 
 
+def _looks_like_wheel(location: str) -> bool:
+    if not location.endswith(WHEEL_EXTENSION):
+        return False
+    if not os.path.isfile(location):
+        return False
+    if not Wheel.wheel_file_re.match(os.path.basename(location)):
+        return False
+    return zipfile.is_zipfile(location)
+
+
 class _DistributionFinder:
     """Finder to locate distributions.
 
@@ -36,6 +48,11 @@ def __init__(self) -> None:
 
     def _find_impl(self, location: str) -> Iterator[FoundResult]:
         """Find distributions in a location."""
+        # Skip looking inside a wheel. Since a package inside a wheel is not
+        # always valid (due to .data directories etc.), its .dist-info entry
+        # should not be considered an installed distribution.
+        if _looks_like_wheel(location):
+            return
         # To know exactly where we find a distribution, we have to feed in the
         # paths one by one, instead of dumping the list to importlib.metadata.
         for dist in importlib.metadata.distributions(path=[location]):

tests/unit/metadata/test_metadata.py

@@ -1,4 +1,5 @@
 import logging
+import os
 from pathlib import Path
 from typing import cast
 from unittest import mock
@@ -9,6 +10,7 @@
 from pip._internal.metadata import (
     BaseDistribution,
     get_directory_distribution,
+    get_environment,
     get_wheel_distribution,
 )
 from pip._internal.metadata.base import FilesystemWheel
@@ -102,3 +104,28 @@ def test_metadata_dict(tmp_path: Path) -> None:
     metadata_dict = dist.metadata_dict
     assert metadata_dict["name"] == "pkga"
     assert metadata_dict["version"] == "1.0.1"
+
+
+def test_no_dist_found_in_wheel(tmp_path: Path) -> None:
+    location = os.fspath(tmp_path.joinpath("pkg-1-py3-none-any.whl"))
+    make_wheel(name="pkg", version="1").save_to(location)
+    assert get_environment([location]).get_distribution("pkg") is None
+
+
+def test_dist_found_in_directory_named_whl(tmp_path: Path) -> None:
+    dir_path = tmp_path.joinpath("pkg-1-py3-none-any.whl")
+    info_path = dir_path.joinpath("pkg-1.dist-info")
+    info_path.mkdir(parents=True)
+    info_path.joinpath("METADATA").write_text("Name: pkg")
+    location = os.fspath(dir_path)
+    dist = get_environment([location]).get_distribution("pkg")
+    assert dist is not None and dist.location is not None
+    assert Path(dist.location) == Path(location)
+
+
+def test_dist_found_in_zip(tmp_path: Path) -> None:
+    location = os.fspath(tmp_path.joinpath("pkg.zip"))
+    make_wheel(name="pkg", version="1").save_to(location)
+    dist = get_environment([location]).get_distribution("pkg")
+    assert dist is not None and dist.location is not None
+    assert Path(dist.location) == Path(location)