Improve error message when invalid directory provided

test/test_plugins.py

@@ -21,6 +21,7 @@
     set_plugin_dirs,
     disable_plugins,
     add_plugin_dirs,
+    get_plugin_spec,
 )
 
 from yt_dlp._globals import (
@@ -50,23 +51,31 @@
 )
 
 
+def reset_plugins():
+    plugin_ies.value = {}
+    plugin_pps.value = {}
+    plugin_dirs.value = ['external']
+    plugin_specs.value = {}
+    all_plugins_loaded.value = False
+    plugins_enabled.value = True
+    # Clearing override plugins is probably difficult
+    for module_name in tuple(sys.modules):
+        for plugin_type in ('extractor', 'postprocessor'):
+            if module_name.startswith(f'{PACKAGE_NAME}.{plugin_type}.'):
+                del sys.modules[module_name]
+
+    importlib.invalidate_caches()
+
+
 class TestPlugins(unittest.TestCase):
 
     TEST_PLUGIN_DIR = TEST_DATA_DIR / PACKAGE_NAME
 
     def setUp(self):
-        plugin_ies.value = {}
-        plugin_pps.value = {}
-        plugin_dirs.value = ['external']
-        plugin_specs.value = {}
-        all_plugins_loaded.value = False
-        plugins_enabled.value = True
-        importlib.invalidate_caches()
-        # Clearing override plugins is probably difficult
-        for module_name in tuple(sys.modules):
-            for plugin_type in ('extractor', 'postprocessor'):
-                if module_name.startswith(f'{PACKAGE_NAME}.{plugin_type}.'):
-                    del sys.modules[module_name]
+        reset_plugins()
+
+    def tearDown(self):
+        reset_plugins()
 
     def test_directories_containing_plugins(self):
         self.assertIn(self.TEST_PLUGIN_DIR, map(Path, directories()))
@@ -207,6 +216,11 @@ def test_set_plugin_dirs(self):
         self.assertIn(f'{PACKAGE_NAME}.extractor.package', sys.modules.keys())
         self.assertIn('PackagePluginIE', plugin_ies.value)
 
+    def test_invalid_plugin_dir(self):
+        set_plugin_dirs('invalid_dir')
+        with self.assertRaises(ValueError):
+            load_plugins(EXTRACTOR_PLUGIN_SPEC)
+
     def test_add_plugin_dirs(self):
         custom_plugin_dir = str(TEST_DATA_DIR / 'plugin_packages')
 
@@ -244,6 +258,14 @@ def test_disable_plugins_already_loaded(self):
         ies = load_plugins(EXTRACTOR_PLUGIN_SPEC)
         self.assertIn('NormalPluginIE', ies)
 
+    def test_get_plugin_spec(self):
+        register_plugin_spec(EXTRACTOR_PLUGIN_SPEC)
+        register_plugin_spec(POSTPROCESSOR_PLUGIN_SPEC)
+
+        self.assertEqual(get_plugin_spec('extractor'), EXTRACTOR_PLUGIN_SPEC)
+        self.assertEqual(get_plugin_spec('postprocessor'), POSTPROCESSOR_PLUGIN_SPEC)
+        self.assertIsNone(get_plugin_spec('invalid'))
+
 
 if __name__ == '__main__':
     unittest.main()

yt_dlp/plugins.py

@@ -118,7 +118,10 @@ def internal_plugin_paths():
 
 
 def candidate_plugin_paths(candidate):
-    yield from Path(candidate).iterdir()
+    candidate_path = Path(candidate)
+    if not candidate_path.is_dir():
+        raise ValueError(f'Invalid plugin directory: {candidate_path}')
+    yield from candidate_path.iterdir()
     yield from internal_plugin_paths()