Draft: Fix warning message for missing METADATA file

news/12446.bugfix.rst

@@ -0,0 +1 @@
+Updated warning message for invalid dist-info directory due to missing METADATA file.

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

@@ -1,6 +1,6 @@
 import importlib.metadata
 import os
-from typing import Any, Optional, Protocol, Tuple, cast
+from typing import Any, Optional, Protocol, Tuple, Union, cast
 
 from pip._vendor.packaging.utils import NormalizedName, canonicalize_name
 
@@ -33,6 +33,12 @@ def name(self) -> str:
     def parent(self) -> "BasePath":
         raise NotImplementedError()
 
+    def joinpath(self, *args: Union[str, os.PathLike[str]]) -> "BasePath":
+        raise NotImplementedError()
+
+    def exists(self) -> bool:
+        raise NotImplementedError()
+
 
 def get_info_location(d: importlib.metadata.Distribution) -> Optional[BasePath]:
     """Find the path to the distribution's metadata directory.
@@ -81,5 +87,8 @@ def get_dist_canonical_name(dist: importlib.metadata.Distribution) -> Normalized
 
     name = cast(Any, dist).name
     if not isinstance(name, str):
+        info_location = get_info_location(dist)
+        if info_location and not info_location.joinpath("METADATA"):
+            raise BadMetadata(dist, reason="missing `METADATA` file")
         raise BadMetadata(dist, reason="invalid metadata entry 'name'")
     return canonicalize_name(name)

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

@@ -10,6 +10,7 @@
     Mapping,
     Optional,
     Sequence,
+    Union,
     cast,
 )
 
@@ -100,8 +101,8 @@ class Distribution(BaseDistribution):
     def __init__(
         self,
         dist: importlib.metadata.Distribution,
-        info_location: Optional[BasePath],
-        installed_location: Optional[BasePath],
+        info_location: Optional[Union[BasePath, pathlib.PurePosixPath]],
+        installed_location: Optional[Union[BasePath, pathlib.PurePosixPath]],
     ) -> None:
         self._dist = dist
         self._info_location = info_location

tests/functional/test_list.py

@@ -751,3 +751,22 @@ def test_list_pep610_editable(script: PipTestEnvironment) -> None:
             break
     else:
         pytest.fail("package 'testpkg' not found in pip list result")
+
+
+def test_list_missing_metadata_warning(script: PipTestEnvironment) -> None:
+    """
+    Test that a warning is shown when a dist-info directory is missing the
+    METADATA file.
+    """
+    # Create a test package and create .dist-info dir without METADATA file
+    pkg_path = create_test_package_with_setup(script, name="testpkg", version="1.0")
+    dist_info_path = pkg_path / "testpkg-1.0.dist-info"
+    dist_info_path.mkdir()
+    dist_info_path.joinpath("RECORD").write_text("")
+
+    # List should show a warning about the missing METADATA file
+    result = script.pip("list", expect_stderr=True)
+    assert "WARNING: Skipping" in result.stderr
+    assert (
+        "due to invalid dist-info directory: missing `METADATA` file" in result.stderr
+    )