Fix cog_app_command_error for group edge case

discord/app_commands/commands.py

@@ -613,7 +613,7 @@ class Command(Generic[GroupT, P, T]):
             if parent.parent is not None:
                 await parent.parent.on_error(interaction, error)
 
-        binding_error_handler = getattr(self.binding, '__app_commands_error_handler__', None)
+        binding_error_handler = getattr(self.binding, '__discord_app_commands_error_handler__', None)
         if binding_error_handler is not None:
             await binding_error_handler(interaction, error)
 
@@ -1143,6 +1143,9 @@ class Group:
     __discord_app_commands_guild_only__: bool = MISSING
     __discord_app_commands_default_permissions__: Optional[Permissions] = MISSING
     __discord_app_commands_has_module__: bool = False
+    __discord_app_commands_error_handler__: Optional[
+        Callable[[Interaction, AppCommandError], Coroutine[Any, Any, None]]
+    ] = None
 
     def __init_subclass__(
         cls,
@@ -1269,10 +1272,6 @@ class Group:
                 raise ValueError('groups can only be nested at most one level')
             parent.add_command(self)
 
-        self.__app_commands_error_handler__: Optional[
-            Callable[[Interaction, AppCommandError], Coroutine[Any, Any, None]]
-        ] = None
-
     def __set_name__(self, owner: Type[Any], name: str) -> None:
         self._attr = name
         self.module = owner.__module__

discord/ext/commands/cog.py

@@ -268,7 +268,7 @@ class Cog(metaclass=CogMeta):
     __cog_listeners__: List[Tuple[str, str]]
     __cog_is_app_commands_group__: ClassVar[bool] = False
     __cog_app_commands_group__: Optional[app_commands.Group]
-    __app_commands_error_handler__: Optional[
+    __discord_app_commands_error_handler__: Optional[
         Callable[[discord.Interaction, app_commands.AppCommandError], Coroutine[Any, Any, None]]
     ]
 
@@ -333,7 +333,7 @@ class Cog(metaclass=CogMeta):
         else:
             error_handler = None
 
-        self.__app_commands_error_handler__ = error_handler
+        self.__discord_app_commands_error_handler__ = error_handler
 
         for command in cls.__cog_app_commands__:
             copy = command._copy_with(parent=self.__cog_app_commands_group__, binding=self)
@@ -343,7 +343,10 @@ class Cog(metaclass=CogMeta):
                 setattr(self, copy._attr, copy)
 
             if isinstance(copy, app_commands.Group):
-                copy.__app_commands_error_handler__ = error_handler
+                copy.__discord_app_commands_error_handler__ = error_handler
+                for command in copy._children.values():
+                    if isinstance(command, app_commands.Group):
+                        command.__discord_app_commands_error_handler__ = error_handler
 
             children.append(copy)