Prefer an OO approach for _normalized_name. Allows other providers to supply _normalized_name.

Author: jaraco

importlib_metadata/__init__.py

@@ -20,7 +20,6 @@
     NullFinder,
     PyPy_repr,
     install,
-    singledispatch,
 )
 from ._functools import method_cache
 from ._itertools import unique_everseen
@@ -499,6 +498,11 @@ def name(self):
         """Return the 'Name' metadata for the distribution package."""
         return self.metadata['Name']
 
+    @property
+    def _normalized_name(self):
+        """Return a normalized version of the name."""
+        return Prepared.normalize(self.name)
+
     @property
     def version(self):
         """Return the 'Version' metadata for the distribution package."""
@@ -806,6 +810,12 @@ def read_text(self, filename):
     def locate_file(self, path):
         return self._path.parent / path
 
+    @property
+    def _normalized_name(self):
+        stem = os.path.basename(str(self._path))
+        name, sep, rest = stem.partition('-')
+        return name
+
 
 def distribution(distribution_name):
     """Get the ``Distribution`` instance for the named package.
@@ -843,18 +853,6 @@ 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.
 
@@ -872,7 +870,8 @@ def entry_points(**params) -> Union[EntryPoints, SelectableGroups]:
 
     :return: EntryPoints or SelectableGroups for all installed packages.
     """
-    unique = functools.partial(unique_everseen, key=normalized_name)
+    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())
     )

importlib_metadata/_compat.py

@@ -15,12 +15,6 @@
     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

@@ -21,7 +21,6 @@ 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 =