Use normalized names to distinguish unique distributions for performance. Fixes #283.

Author: jaraco

importlib_metadata/__init__.py

@@ -20,6 +20,7 @@
     NullFinder,
     PyPy_repr,
     install,
+    singledispatch,
 )
 from ._functools import method_cache
 from ._itertools import unique_everseen
@@ -842,6 +843,18 @@ def version(distribution_name):
     return distribution(distribution_name).version
 
 
+@singledispatch
+def normalized_name(dist: Distribution):
+    return Prepared.normalize(dist.name)
+
+
+@normalized_name.register
+def _(dist: PathDistribution):
+    stem = os.path.basename(str(dist._path))
+    name, sep, rest = stem.partition('-')
+    return name
+
+
 def entry_points(**params) -> Union[EntryPoints, SelectableGroups]:
     """Return EntryPoint objects for all installed packages.
 
@@ -859,7 +872,7 @@ def entry_points(**params) -> Union[EntryPoints, SelectableGroups]:
 
     :return: EntryPoints or SelectableGroups for all installed packages.
     """
-    unique = functools.partial(unique_everseen, key=operator.attrgetter('name'))
+    unique = functools.partial(unique_everseen, key=normalized_name)
     eps = itertools.chain.from_iterable(
         dist.entry_points for dist in unique(distributions())
     )

importlib_metadata/_compat.py

@@ -15,6 +15,12 @@
     from typing_extensions import Protocol  # type: ignore
 
 
+if sys.version_info < (3, 7):
+    from singledispatch import singledispatch
+else:
+    from functools import singledispatch  # noqa: F401
+
+
 def install(cls):
     """
     Class decorator for installation on sys.meta_path.

setup.cfg

@@ -21,6 +21,7 @@ python_requires = >=3.6
 install_requires =
 	zipp>=0.5
 	typing-extensions>=3.6.4; python_version < "3.8"
+	singledispatch; python_version < "3.7"
 
 [options.packages.find]
 exclude =