fix: better error message for broken Distribution objects (#508)

importlib_metadata/__init__.py

@@ -563,7 +563,12 @@ def _ensure_metadata_present(self, text: str | None) -> str:
     @property
     def name(self) -> str:
         """Return the 'Name' metadata for the distribution package."""
-        return self.metadata['Name']
+        try:
+            return self.metadata['Name']
+        except KeyError:
+            raise KeyError(
+                f'No Name metadata found for {getattr(self, "_path", self)}'
+            ) from None
 
     @property
     def _normalized_name(self):

tests/test_main.py

@@ -169,6 +169,19 @@ def test_missing_metadata(self):
         with self.assertRaises(MetadataNotFound):
             metadata('foo')
 
+    def test_missing_name_metadata(self):
+        """
+        Dists with metadata but no Name should raise a KeyError
+        with a useful message identifying the distribution.
+
+        Ref python/importlib_metadata#508.
+        """
+        fixtures.build_files(self.make_pkg('foo-4.4'), self.site_dir)
+        dist = Distribution.at(self.site_dir / 'foo-4.4.dist-info')
+        with self.assertRaises(KeyError) as ctx:
+            dist.name
+        assert 'foo-4.4.dist-info' in str(ctx.exception)
+
 
 class NonASCIITests(fixtures.OnSysPath, fixtures.SiteDir, unittest.TestCase):
     @staticmethod