Workaround missing distribution name

Author: abravalheri

importlib_metadata/__init__.py

@@ -29,7 +29,7 @@
 from importlib import import_module
 from importlib.abc import MetaPathFinder
 from itertools import starmap
-from typing import List, Mapping, Optional, Tuple, Union
+from typing import List, Mapping, Optional, Tuple, Union, cast
 
 
 __all__ = [
@@ -1031,12 +1031,19 @@ def version(distribution_name):
 
 def _compat_normalized_name(dist: Distribution) -> Optional[str]:
     """
-    Compatibility layer that honor name normalization for distributions
+    Compatibility shim to honor name normalization for distributions
     that don't provide ``_normalized_name``
     (as in ``importlib.metadata`` for Python 3.8/3.9).
     """
-    normalized = getattr(dist, '_normalized_name', None)
-    return normalized or Prepared.normalize(getattr(dist, "name", ""))
+    try:
+        return dist._normalized_name
+    except AttributeError:
+        if "PathDistribution" in dist.__class__.__name__:
+            dist_ = cast(PathDistribution, dist)  # old implementation
+            return PathDistribution(dist_._path)._normalized_name
+        elif hasattr(dist, "name"):
+            return Prepared.normalize(dist.name)
+        raise
 
 
 _unique = functools.partial(

tests/test_integration.py

@@ -56,11 +56,26 @@ def setUp(self):
         super().setUp()
 
     def _meta_path_finder(self):
-        from importlib.metadata import DistributionFinder, PathDistribution
+        from importlib.metadata import (
+            Distribution,
+            DistributionFinder,
+            PathDistribution,
+        )
         from importlib.util import spec_from_file_location
 
         path = pathlib.Path(self.site_dir)
 
+        class CustomDistribution(Distribution):
+            def __init__(self, name, path):
+                self.name = name
+                self._path_distribution = PathDistribution(path)
+
+            def read_text(self, filename):
+                return self._path_distribution.read_text(filename)
+
+            def locate_file(self, path):
+                return self._path_distribution.locate_file(path)
+
         class CustomFinder:
             @classmethod
             def find_spec(cls, fullname, _path=None, _target=None):
@@ -72,6 +87,8 @@ def find_spec(cls, fullname, _path=None, _target=None):
             def find_distributions(self, context=DistributionFinder.Context()):
                 for dist_info in path.glob("*.dist-info"):
                     yield PathDistribution(dist_info)
+                    name, _, _ = str(dist_info).partition("-")
+                    yield CustomDistribution(name + "_custom", dist_info)
 
         return CustomFinder
 
@@ -85,8 +102,11 @@ def test_compatibility_with_old_stdlib_path_distribution(self):
 
         assert list(distributions())
         assert distribution("distinfo_pkg")
+        assert distribution("distinfo_pkg_custom")
         assert version("distinfo_pkg") > "0"
+        assert version("distinfo_pkg_custom") > "0"
         assert list(metadata("distinfo_pkg"))
+        assert list(metadata("distinfo_pkg_custom"))
         assert list(entry_points(group="entries"))