[Fix] Fix RecursionError when key is invalid (#220)

* [Fix] Fix RecursionError when key is invalid

* refine comments

mmengine/registry/registry.py

@@ -301,7 +301,7 @@ class Registry:
 
         Args:
             key (str): Name of the registered item, e.g., the class name in
-            string format.
+                string format.
 
         Returns:
             Type or None: Return the corresponding class if ``key`` exists,
@@ -355,7 +355,14 @@ class Registry:
                 scope_name = scope
             else:
                 root = self._get_root_registry()
-                obj_cls = root.get(key)
+
+                if scope != root._scope and scope not in root._children:
+                    # If not skip directly, `root.get(key)` will recursively
+                    # call itself until RecursionError is thrown.
+                    pass
+                else:
+                    obj_cls = root.get(key)
+
         if obj_cls is not None:
             logger: MMLogger = MMLogger.get_current_instance()
             logger.info(

tests/test_registry/test_registry.py

@@ -281,6 +281,16 @@ class TestRegistry:
         assert HOUNDS.get('samoyed.little_samoyed.LittlePedigreeSamoyed'
                           ) is LittlePedigreeSamoyed
 
+        # invalid keys
+        # GoldenRetrieverererer can not be found at LITTLE_HOUNDS modules
+        assert LITTLE_HOUNDS.get('GoldenRetrieverererer') is None
+        # samoyedddd is not a child of DOGS
+        assert DOGS.get('samoyedddd.PedigreeSamoyed') is None
+        # samoyed is a child of DOGS but LittlePedigreeSamoyed can not be found
+        # at SAMOYEDS modules
+        assert DOGS.get('samoyed.LittlePedigreeSamoyed') is None
+        assert LITTLE_HOUNDS.get('mid_hound.PedigreeSamoyedddddd') is None
+
     def test_search_child(self):
         #        Hierarchical Registry
         #                           DOGS