Ensure explicitly set parents on nested groups are respected

This had a multiple layer bug that needed to be squashed. The first
issue was that setting `parent=...` inside a `Group` wouldn't actually
add the `Group` into the `parent` children mapping. This meant that
it didn't actually end up copying the children when it came time to
within e.g. a Cog.

The second issue was that even if it was added into the children
listing, it wouldn't properly set the attribute.

This commit fixes both of these issues.

Fix #7818

discord/app_commands/commands.py

@@ -971,6 +971,7 @@ class Group:
         self.name: str = validate_name(name) if name is not MISSING else cls.__discord_app_commands_group_name__
         self.description: str = description or cls.__discord_app_commands_group_description__
         self._attr: Optional[str] = None
+        self._owner_cls: Optional[Type[Any]] = None
         self._guild_ids: Optional[List[int]] = guild_ids
 
         if not self.description:
@@ -1004,12 +1005,15 @@ class Group:
             if copy._attr and not cls.__discord_app_commands_skip_init_binding__:
                 setattr(self, copy._attr, copy)
 
-        if parent is not None and parent.parent is not None:
-            raise ValueError('groups can only be nested at most one level')
+        if parent is not None:
+            if parent.parent is not None:
+                raise ValueError('groups can only be nested at most one level')
+            parent.add_command(self)
 
     def __set_name__(self, owner: Type[Any], name: str) -> None:
         self._attr = name
         self.module = owner.__module__
+        self._owner_cls = owner
 
     def _copy_with(
         self,
@@ -1029,6 +1033,7 @@ class Group:
         copy.parent = parent
         copy.module = self.module
         copy._attr = self._attr
+        copy._owner_cls = self._owner_cls
         copy._children = {}
 
         bindings[self] = copy
@@ -1038,6 +1043,12 @@ class Group:
             child_copy.parent = copy
             copy._children[child_copy.name] = child_copy
 
+            if isinstance(child_copy, Group) and child_copy._attr and set_on_binding:
+                if binding.__class__ is child_copy._owner_cls:
+                    setattr(binding, child_copy._attr, child_copy)
+                elif child_copy._owner_cls is copy.__class__:
+                    setattr(copy, child_copy._attr, child_copy)
+
         if copy._attr and set_on_binding:
             setattr(parent or binding, copy._attr, copy)
 

tests/test_app_commands_group.py

@@ -95,8 +95,7 @@ def test_group_subclass_with_group_subclass():
     assert my_group.my_group_command.parent is my_group
     assert my_group.my_group_command.binding is my_group
     assert my_group.sub_group.my_sub_group_command.parent is my_group.sub_group
-    print(my_group.sub_group.my_sub_group_command.binding)
-    print(MyGroup.sub_group)
+    assert not hasattr(my_group, 'my_sub_group_command')
     assert my_group.sub_group.my_sub_group_command.binding is my_group.sub_group
 
 
@@ -127,6 +126,32 @@ def test_cog_with_group_with_commands():
     assert cog.my_command.binding is cog
 
 
+def test_cog_with_nested_group_with_commands():
+    class MyCog(commands.Cog):
+        first = app_commands.Group(name='test', description='Test 1')
+        second = app_commands.Group(name='test2', parent=first, description='Test 2')
+
+        @first.command(name='cmd')
+        async def test_cmd(self, interaction: discord.Interaction) -> None:
+            ...
+
+        @second.command(name='cmd2')
+        async def test2_cmd(self, interaction: discord.Interaction) -> None:
+            ...
+
+    cog = MyCog()
+
+    assert len(MyCog.__cog_app_commands__) == 1
+    assert cog.first.parent is None
+    assert cog.first is not MyCog.first
+    assert cog.second is not MyCog.second
+    assert cog.second.parent is cog.first
+    assert cog.test_cmd.parent is cog.first
+    assert cog.test2_cmd.parent is cog.second
+    assert cog.test_cmd.binding is cog
+    assert cog.test2_cmd.binding is cog
+
+
 def test_cog_with_group_subclass_with_commands():
     class MyGroup(app_commands.Group, name='mygroup'):
         @app_commands.command()
@@ -175,6 +200,8 @@ def test_cog_with_group_subclass_with_group():
     assert cog.my_group.my_command is not MyGroup.my_command
     assert cog.my_cog_command is not MyCog.my_cog_command
     assert not hasattr(cog.my_group, 'my_cog_command')
+    assert not hasattr(cog, 'sub_group')
+    assert not hasattr(cog, 'my_command')
     assert cog.my_group.parent is None
     assert cog.my_group.sub_group.parent is cog.my_group
     assert cog.my_group.my_command.parent is cog.my_group.sub_group
@@ -215,6 +242,10 @@ def test_cog_with_group_subclass_with_group_subclass():
     assert cog.my_group.sub_group is not MyGroup.sub_group
     assert cog.my_cog_command is not MyCog.my_cog_command
     assert not hasattr(cog.my_group, 'my_cog_command')
+    assert not hasattr(cog, 'sub_group')
+    assert not hasattr(cog, 'my_group_command')
+    assert not hasattr(cog, 'my_sub_group_command')
+    assert not hasattr(cog.my_group, 'my_sub_group_command')
     assert cog.my_group.sub_group.my_sub_group_command is not MyGroup.sub_group.my_sub_group_command
     assert cog.my_group.sub_group.my_sub_group_command is not MySubGroup.my_sub_group_command
     assert cog.my_group.sub_group.parent is cog.my_group