Infer top-level names for a package

CHANGES.rst

@@ -1,3 +1,10 @@
+v4.7.0
+======
+
+* #330: In ``packages_distributions``, now infer top-level
+  names from ``.files()`` when a ``top-level.txt``
+  (Setuptools-specific metadata) is not present.
+
 v4.6.4
 ======
 

importlib_metadata/__init__.py

@@ -1013,6 +1013,18 @@ def packages_distributions() -> Mapping[str, List[str]]:
     """
     pkg_to_dist = collections.defaultdict(list)
     for dist in distributions():
-        for pkg in (dist.read_text('top_level.txt') or '').split():
+        for pkg in _top_level_declared(dist) or _top_level_inferred(dist):
             pkg_to_dist[pkg].append(dist.metadata['Name'])
     return dict(pkg_to_dist)
+
+
+def _top_level_declared(dist):
+    return (dist.read_text('top_level.txt') or '').split()
+
+
+def _top_level_inferred(dist):
+    return {
+        f.parts[0] if len(f.parts) > 1 else f.with_suffix('').name
+        for f in dist.files
+        if f.suffix == ".py"
+    }

prepare/example2/example2/__init__.py

@@ -0,0 +1,2 @@
+def main():
+    return "example"

prepare/example2/pyproject.toml

@@ -0,0 +1,10 @@
+[build-system]
+build-backend = 'trampolim'
+requires = ['trampolim']
+
+[project]
+name = 'example2'
+version = '1.0.0'
+
+[project.scripts]
+example = 'example2:main'

tests/fixtures.py

@@ -301,7 +301,7 @@ class ZipFixtures:
     def _fixture_on_path(self, filename):
         pkg_file = resources.files(self.root).joinpath(filename)
         file = self.resources.enter_context(resources.as_file(pkg_file))
-        assert file.name.startswith('example-'), file.name
+        assert file.name.startswith('example'), file.name
         sys.path.insert(0, str(file))
         self.resources.callback(sys.path.pop, 0)
 

tests/test_main.py

@@ -17,6 +17,7 @@
     distributions,
     entry_points,
     metadata,
+    packages_distributions,
     version,
 )
 
@@ -282,3 +283,17 @@ def test_unicode_dir_on_sys_path(self):
             prefix=self.site_dir,
         )
         list(distributions())
+
+
+class PackagesDistributionsTest(fixtures.ZipFixtures, unittest.TestCase):
+    def test_packages_distributions_example(self):
+        self._fixture_on_path('example-21.12-py3-none-any.whl')
+        assert packages_distributions()['example'] == ['example']
+
+    def test_packages_distributions_example2(self):
+        """
+        Test packages_distributions on a wheel built
+        by trampolim.
+        """
+        self._fixture_on_path('example2-1.0.0-py3-none-any.whl')
+        assert packages_distributions()['example2'] == ['example2']