Merge pull request #382 from python/feature/unique-distributions-func…

…tion

Extract _unique function for testing and potential public exposure.

importlib_metadata/__init__.py

@@ -1015,6 +1015,15 @@ def version(distribution_name):
     return distribution(distribution_name).version
 
 
+_unique = functools.partial(
+    unique_everseen,
+    key=operator.attrgetter('_normalized_name'),
+)
+"""
+Wrapper for ``distributions`` to return unique distributions by name.
+"""
+
+
 def entry_points(**params) -> Union[EntryPoints, SelectableGroups]:
     """Return EntryPoint objects for all installed packages.
 
@@ -1032,10 +1041,8 @@ def entry_points(**params) -> Union[EntryPoints, SelectableGroups]:
 
     :return: EntryPoints or SelectableGroups for all installed packages.
     """
-    norm_name = operator.attrgetter('_normalized_name')
-    unique = functools.partial(unique_everseen, key=norm_name)
     eps = itertools.chain.from_iterable(
-        dist.entry_points for dist in unique(distributions())
+        dist.entry_points for dist in _unique(distributions())
     )
     return SelectableGroups.load(eps).select(**params)
 

tests/test_main.py

@@ -13,6 +13,7 @@
     EntryPoint,
     MetadataPathFinder,
     PackageNotFoundError,
+    _unique,
     distributions,
     entry_points,
     metadata,
@@ -105,6 +106,21 @@ def test_dist_name_found_as_any_case(self):
         assert version(pkg_name.lower()) == '1.0'
         assert version(pkg_name.upper()) == '1.0'
 
+    def test_unique_distributions(self):
+        """
+        Two distributions varying only by non-normalized name on
+        the file system should resolve as the same.
+        """
+        fixtures.build_files(self.make_pkg('abc'), self.site_dir)
+        before = list(_unique(distributions()))
+
+        alt_site_dir = self.fixtures.enter_context(fixtures.tempdir())
+        self.fixtures.enter_context(self.add_sys_path(alt_site_dir))
+        fixtures.build_files(self.make_pkg('ABC'), alt_site_dir)
+        after = list(_unique(distributions()))
+
+        assert len(after) == len(before)
+
 
 class NonASCIITests(fixtures.OnSysPath, fixtures.SiteDir, unittest.TestCase):
     @staticmethod