Allow migrations in namespace packages without __init__.py

Remove obsolete __file__ check to support Python 3 implicit namespace
packages as valid migration modules. This enables migrations to work in
directories lacking __init__.py files.

Refs #29091.

django/db/migrations/loader.py

@@ -84,11 +84,6 @@ class MigrationLoader:
                     continue
                 raise
             else:
-                # Empty directories are namespaces.
-                # getattr() needed on PY36 and older (replace w/attribute access).
-                if getattr(module, '__file__', None) is None:
-                    self.unmigrated_apps.add(app_config.label)
-                    continue
                 # Module is not a package (e.g. migrations.py).
                 if not hasattr(module, '__path__'):
                     self.unmigrated_apps.add(app_config.label)

tests/migrations/test_loader.py

@@ -190,11 +190,37 @@ class LoaderTests(TestCase):
             )
 
     def test_load_empty_dir(self):
+        """
+        A namespace package (directory without __init__.py) can be a valid
+        migrations module even when it has no migration files. It's treated
+        the same as a regular package with no migrations.
+        """
         with override_settings(MIGRATION_MODULES={"migrations": "migrations.faulty_migrations.namespace"}):
             loader = MigrationLoader(connection)
             self.assertIn(
-                "migrations", loader.unmigrated_apps,
+                "migrations", loader.migrated_apps,
-                "App missing __init__.py in migrations module not in unmigrated apps."
+                "Namespace package should be in migrated apps even without migrations."
+            )
+            # Ensure no migrations were actually loaded
+            migration_count = len([
+                key for key in loader.disk_migrations if key[0] == "migrations"
+            ])
+            self.assertEqual(migration_count, 0)
+
+    @override_settings(MIGRATION_MODULES={"migrations": "migrations.test_migrations_namespace_package"})
+    def test_namespace_package_with_migrations(self):
+        """
+        Namespace packages (directories without __init__.py) can contain
+        migration files and should be loaded correctly.
+        """
+        loader = MigrationLoader(connection)
+        self.assertIn(
+            "migrations", loader.migrated_apps,
+            "Namespace package with migrations should be in migrated apps."
+        )
+        self.assertIn(
+            ("migrations", "0001_initial"), loader.disk_migrations,
+            "Migration from namespace package should be loaded."
         )
 
     @override_settings(

tests/migrations/test_migrations_namespace_package/0001_initial.py

@@ -0,0 +1,16 @@
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    initial = True
+
+    operations = [
+        migrations.CreateModel(
+            "Author",
+            [
+                ("id", models.AutoField(primary_key=True)),
+                ("name", models.CharField(max_length=255)),
+            ],
+        ),
+    ]