gh-59022: Added tests for pkgutil.extend_path (#59022)

This adds tests for the documented behaviour of `pkgutil.extend_path`
regarding different argument types as well as for `*.pkg` files.

Author: beachmachine

Lib/test/test_pkgutil.py

@@ -522,7 +522,42 @@ def test_mixed_namespace(self):
         del sys.modules['foo.bar']
         del sys.modules['foo.baz']
 
-    # XXX: test .pkg files
+
+    def test_extend_path_argument_types(self):
+        pkgname = 'foo'
+        dirname_0 = self.create_init(pkgname)
+
+        # If the input path is not a list it is returned unchanged
+        self.assertEqual('notalist', pkgutil.extend_path('notalist', 'foo'))
+        self.assertEqual(('not', 'a', 'list'), pkgutil.extend_path(('not', 'a', 'list'), 'foo'))
+        self.assertEqual(123, pkgutil.extend_path(123, 'foo'))
+        self.assertEqual(None, pkgutil.extend_path(None, 'foo'))
+
+        # Cleanup
+        shutil.rmtree(dirname_0)
+
+
+    def test_extend_path_pkg_files(self):
+        pkgname = 'foo'
+        dirname_0 = self.create_init(pkgname)
+
+        with open(os.path.join(dirname_0, 'bar.pkg'), 'w') as pkg_file:
+            pkg_file.write('\n'.join([
+                'baz',
+                '/foo/bar/baz',
+                '',
+                '#comment'
+            ]))
+
+        # A *.pkg file is trusted at face value. Apart from checking for duplicates, all entries found in a *.pkg
+        # file are added as-is to the resulting paths, regardless of whether they exist on the filesystem.
+        extended_paths = pkgutil.extend_path(sys.path, 'bar')
+
+        self.assertEqual(extended_paths[-2], 'baz')
+        self.assertEqual(extended_paths[-1], '/foo/bar/baz')
+
+        # Cleanup
+        shutil.rmtree(dirname_0)
 
 
 class NestedNamespacePackageTest(unittest.TestCase):

Misc/NEWS.d/next/Tests/2024-07-13-11-48-20.gh-issue-59022.fYNbQ8.rst

@@ -0,0 +1 @@
+Add tests for :class:`pkgutil.extend_path`. Patch by Andreas Stocker.