[commands] Allow Cog and app_commands interopability

This changeset allows app commands defined inside Cog to work as
expected. Likewise, by deriving app_commands.Group and Cog you can
make the cog function as a top level command on Discord.

discord/app_commands/commands.py

@@ -61,6 +61,11 @@ if TYPE_CHECKING:
     from .namespace import Namespace
     from .models import ChoiceT
 
+    # Generally, these two libraries are supposed to be separate from each other.
+    # However, for type hinting purposes it's unfortunately necessary for one to
+    # reference the other to prevent type checking errors in callbacks
+    from discord.ext.commands import Cog
+
 __all__ = (
     'Command',
     'ContextMenu',
@@ -79,7 +84,7 @@ else:
     P = TypeVar('P')
 
 T = TypeVar('T')
-GroupT = TypeVar('GroupT', bound='Group')
+GroupT = TypeVar('GroupT', bound='Union[Group, Cog]')
 Coro = Coroutine[Any, Any, T]
 Error = Union[
     Callable[[GroupT, Interaction, AppCommandError], Coro[Any]],
@@ -628,15 +633,14 @@ class Group:
     """
 
     __discord_app_commands_group_children__: ClassVar[List[Union[Command, Group]]] = []
+    __discord_app_commands_skip_init_binding__: bool = False
     __discord_app_commands_group_name__: str = MISSING
     __discord_app_commands_group_description__: str = MISSING
 
     def __init_subclass__(cls, *, name: str = MISSING, description: str = MISSING) -> None:
         if not cls.__discord_app_commands_group_children__:
             cls.__discord_app_commands_group_children__ = children = [
-                member
-                for member in cls.__dict__.values()
-                if isinstance(member, (Group, Command)) and member.parent is None
+                member for member in cls.__dict__.values() if isinstance(member, (Group, Command)) and member.parent is None
             ]
 
             found = set()
@@ -661,7 +665,6 @@ class Group:
         else:
             cls.__discord_app_commands_group_description__ = description
 
-
     def __init__(
         self,
         *,
@@ -683,10 +686,10 @@ class Group:
         self._children: Dict[str, Union[Command, Group]] = {}
 
         for child in self.__discord_app_commands_group_children__:
-            child = child._copy_with_binding(self)
+            child = child._copy_with_binding(self) if not cls.__discord_app_commands_skip_init_binding__ else child
             child.parent = self
             self._children[child.name] = child
-            if child._attr:
+            if child._attr and not cls.__discord_app_commands_skip_init_binding__:
                 setattr(self, child._attr, child)
 
         if parent is not None and parent.parent is not None:
@@ -695,7 +698,7 @@ class Group:
     def __set_name__(self, owner: Type[Any], name: str) -> None:
         self._attr = name
 
-    def _copy_with_binding(self, binding: Group) -> Group:
+    def _copy_with_binding(self, binding: Union[Group, Cog]) -> Group:
         cls = self.__class__
         copy = cls.__new__(cls)
         copy.name = self.name

discord/ext/commands/bot.py

@@ -36,6 +36,8 @@ import types
 from typing import Any, Callable, Mapping, List, Dict, TYPE_CHECKING, Optional, TypeVar, Type, Union, overload
 
 import discord
+from discord import app_commands
+from discord.app_commands.tree import _retrieve_guild_ids
 
 from .core import GroupMixin
 from .view import StringView
@@ -50,7 +52,7 @@ if TYPE_CHECKING:
     import importlib.machinery
 
     from discord.message import Message
-    from discord.abc import User
+    from discord.abc import User, Snowflake
     from ._types import (
         Check,
         CoroFunc,
@@ -135,6 +137,8 @@ class BotBase(GroupMixin):
         super().__init__(**options)
         self.command_prefix = command_prefix
         self.extra_events: Dict[str, List[CoroFunc]] = {}
+        # Self doesn't have the ClientT bound, but since this is a mixin it technically does
+        self.__tree: app_commands.CommandTree[Self] = app_commands.CommandTree(self)  # type: ignore
         self.__cogs: Dict[str, Cog] = {}
         self.__extensions: Dict[str, types.ModuleType] = {}
         self._checks: List[Check] = []
@@ -529,11 +533,22 @@ class BotBase(GroupMixin):
 
     # cogs
 
-    def add_cog(self, cog: Cog, /, *, override: bool = False) -> None:
+    def add_cog(
+        self,
+        cog: Cog,
+        /,
+        *,
+        override: bool = False,
+        guild: Optional[Snowflake] = MISSING,
+        guilds: List[Snowflake] = MISSING,
+    ) -> None:
         """Adds a "cog" to the bot.
 
         A cog is a class that has its own event listeners and commands.
 
+        If the cog is a :class:`.app_commands.Group` then it is added to
+        the bot's :class:`~discord.app_commands.CommandTree` as well.
+
         .. versionchanged:: 2.0
 
             :exc:`.ClientException` is raised when a cog with the same name
@@ -551,6 +566,19 @@ class BotBase(GroupMixin):
             If a previously loaded cog with the same name should be ejected
             instead of raising an error.
 
+            .. versionadded:: 2.0
+        guild: Optional[:class:`~discord.abc.Snowflake`]
+            If the cog is an application command group, then this would be the
+            guild where the cog group would be added to. If not given then
+            it becomes a global command instead.
+
+            .. versionadded:: 2.0
+        guilds: List[:class:`~discord.abc.Snowflake`]
+            If the cog is an application command group, then this would be the
+            guilds where the cog group would be added to. If not given then
+            it becomes a global command instead. Cannot be mixed with
+            ``guild``.
+
             .. versionadded:: 2.0
 
         Raises
@@ -572,7 +600,10 @@ class BotBase(GroupMixin):
         if existing is not None:
             if not override:
                 raise discord.ClientException(f'Cog named {cog_name!r} already loaded')
-            self.remove_cog(cog_name)
+            self.remove_cog(cog_name, guild=guild, guilds=guilds)
+
+        if isinstance(cog, app_commands.Group):
+            self.__tree.add_command(cog, override=override, guild=guild, guilds=guilds)
 
         cog = cog._inject(self)
         self.__cogs[cog_name] = cog
@@ -600,7 +631,13 @@ class BotBase(GroupMixin):
         """
         return self.__cogs.get(name)
 
-    def remove_cog(self, name: str, /) -> Optional[Cog]:
+    def remove_cog(
+        self,
+        name: str,
+        /,
+        guild: Optional[Snowflake] = MISSING,
+        guilds: List[Snowflake] = MISSING,
+    ) -> Optional[Cog]:
         """Removes a cog from the bot and returns it.
 
         All registered commands and event listeners that the
@@ -616,6 +653,19 @@ class BotBase(GroupMixin):
         -----------
         name: :class:`str`
             The name of the cog to remove.
+        guild: Optional[:class:`~discord.abc.Snowflake`]
+            If the cog is an application command group, then this would be the
+            guild where the cog group would be removed from. If not given then
+            a global command is removed instead instead.
+
+            .. versionadded:: 2.0
+        guilds: List[:class:`~discord.abc.Snowflake`]
+            If the cog is an application command group, then this would be the
+            guilds where the cog group would be removed from. If not given then
+            a global command is removed instead instead. Cannot be mixed with
+            ``guild``.
+
+            .. versionadded:: 2.0
 
         Returns
         -------
@@ -630,6 +680,15 @@ class BotBase(GroupMixin):
         help_command = self._help_command
         if help_command and help_command.cog is cog:
             help_command.cog = None
+
+        if isinstance(cog, app_commands.Group):
+            guild_ids = _retrieve_guild_ids(cog, guild, guilds)
+            if guild_ids is None:
+                self.__tree.remove_command(name)
+            else:
+                for guild_id in guild_ids:
+                    self.__tree.remove_command(name, guild=discord.Object(guild_id))
+
         cog._eject(self)
 
         return cog
@@ -894,6 +953,20 @@ class BotBase(GroupMixin):
         else:
             self._help_command = None
 
+    # application command interop
+
+    # As mentioned above, this is a mixin so the Self type hint fails here.
+    # However, since the only classes that can use this are subclasses of Client
+    # anyway, then this is sound.
+    @property
+    def tree(self) -> app_commands.CommandTree[Self]:  # type: ignore
+        """:class:`~discord.app_commands.CommandTree`: The command tree responsible for handling the application commands
+        in this bot.
+
+        .. versionadded:: 2.0
+        """
+        return self.__tree
+
     # command processing
 
     async def get_prefix(self, message: Message) -> Union[List[str], str]:

discord/ext/commands/cog.py

@@ -24,14 +24,15 @@ DEALINGS IN THE SOFTWARE.
 from __future__ import annotations
 
 import inspect
-import discord.utils
+import discord
+from discord import app_commands
 
-from typing import Any, Callable, ClassVar, Dict, Generator, List, Optional, TYPE_CHECKING, Tuple, TypeVar, Type
+from typing import Any, Callable, Dict, Generator, List, Optional, TYPE_CHECKING, Tuple, TypeVar, Union, Type
 
 from ._types import _BaseCommand
 
 if TYPE_CHECKING:
-    from typing_extensions import Self
+    from typing_extensions import Self, TypeGuard
 
     from .bot import BotBase
     from .context import Context
@@ -110,19 +111,33 @@ class CogMeta(type):
     __cog_name__: str
     __cog_settings__: Dict[str, Any]
     __cog_commands__: List[Command]
+    __cog_is_app_commands_group__: bool
+    __cog_app_commands__: List[Union[app_commands.Group, app_commands.Command[Any, ..., Any]]]
     __cog_listeners__: List[Tuple[str, str]]
 
     def __new__(cls, *args: Any, **kwargs: Any) -> Self:
         name, bases, attrs = args
-        attrs['__cog_name__'] = kwargs.pop('name', name)
+        attrs['__cog_name__'] = kwargs.get('name', name)
         attrs['__cog_settings__'] = kwargs.pop('command_attrs', {})
+        attrs['__cog_is_app_commands_group__'] = is_parent = app_commands.Group in bases
 
-        description = kwargs.pop('description', None)
+        description = kwargs.get('description', None)
         if description is None:
             description = inspect.cleandoc(attrs.get('__doc__', ''))
         attrs['__cog_description__'] = description
 
+        if is_parent:
+            attrs['__discord_app_commands_skip_init_binding__'] = True
+            # This is hacky, but it signals the Group not to process this info.
+            # It's overridden later.
+            attrs['__discord_app_commands_group_children__'] = True
+        else:
+            # Remove the extraneous keyword arguments we're using
+            kwargs.pop('name', None)
+            kwargs.pop('description', None)
+
         commands = {}
+        cog_app_commands = {}
         listeners = {}
         no_bot_cog = 'Commands or listeners must not start with cog_ or bot_ (in method {0.__name__}.{1})'
 
@@ -143,6 +158,8 @@ class CogMeta(type):
                     if elem.startswith(('cog_', 'bot_')):
                         raise TypeError(no_bot_cog.format(base, elem))
                     commands[elem] = value
+                elif isinstance(value, (app_commands.Group, app_commands.Command)) and value.parent is None:
+                    cog_app_commands[elem] = value
                 elif inspect.iscoroutinefunction(value):
                     try:
                         getattr(value, '__cog_listener__')
@@ -154,6 +171,13 @@ class CogMeta(type):
                         listeners[elem] = value
 
         new_cls.__cog_commands__ = list(commands.values())  # this will be copied in Cog.__new__
+        new_cls.__cog_app_commands__ = list(cog_app_commands.values())
+
+        if is_parent:
+            # Prefill the app commands for the Group as well..
+            # The type checker doesn't like runtime attribute modification and this one's
+            # optional so it can't be cheesed.
+            new_cls.__discord_app_commands_group_children__ = cog_app_commands  # type: ignore
 
         listeners_as_list = []
         for listener in listeners.values():
@@ -189,10 +213,11 @@ class Cog(metaclass=CogMeta):
     are equally valid here.
     """
 
-    __cog_name__: ClassVar[str]
-    __cog_settings__: ClassVar[Dict[str, Any]]
-    __cog_commands__: ClassVar[List[Command[Self, ..., Any]]]
-    __cog_listeners__: ClassVar[List[Tuple[str, str]]]
+    __cog_name__: str
+    __cog_settings__: Dict[str, Any]
+    __cog_commands__: List[Command[Self, ..., Any]]
+    __cog_app_commands__: List[Union[app_commands.Group, app_commands.Command[Self, ..., Any]]]
+    __cog_listeners__: List[Tuple[str, str]]
 
     def __new__(cls, *args: Any, **kwargs: Any) -> Self:
         # For issue 426, we need to store a copy of the command objects
@@ -219,6 +244,25 @@ class Cog(metaclass=CogMeta):
                 parent.remove_command(command.name)  # type: ignore
                 parent.add_command(command)  # type: ignore
 
+        # Register the application commands
+        children: List[Union[app_commands.Group, app_commands.Command[Self, ..., Any]]] = []
+        for command in cls.__cog_app_commands__:
+            copy = command._copy_with_binding(self)
+
+            if cls.__cog_is_app_commands_group__:
+                # Type checker doesn't understand this type of narrowing.
+                # Not even with TypeGuard somehow.
+                copy.parent = self  # type: ignore
+
+            children.append(copy)
+            if command._attr:
+                setattr(self, command._attr, copy)
+
+        self.__cog_app_commands__ = children
+        if cls.__cog_is_app_commands_group__:
+            # Dynamic attribute setting
+            self.__discord_app_commands_group_children__ = children  # type: ignore
+
         return self
 
     def get_commands(self) -> List[Command[Self, ..., Any]]:
@@ -452,6 +496,12 @@ class Cog(metaclass=CogMeta):
         for name, method_name in self.__cog_listeners__:
             bot.add_listener(getattr(self, method_name), name)
 
+        # Only do this if these are "top level" commands
+        if not cls.__cog_is_app_commands_group__:
+            for command in self.__cog_app_commands__:
+                # This is already atomic
+                bot.tree.add_command(command)
+
         return self
 
     def _eject(self, bot: BotBase) -> None:
@@ -462,6 +512,16 @@ class Cog(metaclass=CogMeta):
                 if command.parent is None:
                     bot.remove_command(command.name)
 
+            if not cls.__cog_is_app_commands_group__:
+                for command in self.__cog_app_commands__:
+                    try:
+                        guild_ids = command.__discord_app_commands_default_guilds__
+                    except AttributeError:
+                        bot.tree.remove_command(command.name)
+                    else:
+                        for guild_id in guild_ids:
+                            bot.tree.remove_command(command.name, guild=discord.Object(id=guild_id))
+
             for name, method_name in self.__cog_listeners__:
                 bot.remove_listener(getattr(self, method_name), name)