Fix GuildChannel subclasses not working with default select values

This also fixes it so ClientUser is respected as well

discord/ui/select.py

@@ -55,7 +55,9 @@ from ..app_commands.namespace import Namespace
 from ..member import Member
 from ..object import Object
 from ..role import Role
-from ..user import User
+from ..user import User, ClientUser
+
+# from ..channel import TextChannel, VoiceChannel, StageChannel, CategoryChannel, ForumChannel
 from ..abc import GuildChannel
 from ..threads import Thread
 
@@ -69,7 +71,7 @@ __all__ = (
 )
 
 if TYPE_CHECKING:
-    from typing_extensions import TypeAlias, Self
+    from typing_extensions import TypeAlias, Self, TypeGuard
 
     from .view import View
     from ..types.components import SelectMenu as SelectMenuPayload
@@ -92,6 +94,7 @@ if TYPE_CHECKING:
         Object,
         Role,
         Member,
+        ClientUser,
         User,
         GuildChannel,
         AppCommandChannel,
@@ -107,18 +110,26 @@ RoleSelectT = TypeVar('RoleSelectT', bound='RoleSelect[Any]')
 ChannelSelectT = TypeVar('ChannelSelectT', bound='ChannelSelect[Any]')
 MentionableSelectT = TypeVar('MentionableSelectT', bound='MentionableSelect[Any]')
 SelectCallbackDecorator: TypeAlias = Callable[[ItemCallbackType[V, BaseSelectT]], BaseSelectT]
+DefaultSelectComponentTypes = Literal[
+    ComponentType.user_select,
+    ComponentType.role_select,
+    ComponentType.channel_select,
+    ComponentType.mentionable_select,
+]
 
 selected_values: ContextVar[Dict[str, List[PossibleValue]]] = ContextVar('selected_values')
 
 
+def _is_valid_object_type(
+    obj: Any,
+    component_type: DefaultSelectComponentTypes,
+    type_to_supported_classes: Dict[ValidSelectType, Tuple[Type[ValidDefaultValues], ...]],
+) -> TypeGuard[Type[ValidDefaultValues]]:
+    return issubclass(obj, type_to_supported_classes[component_type])
+
+
 def _handle_select_defaults(
-    defaults: Sequence[ValidDefaultValues],
-    component_type: Literal[
-        ComponentType.user_select,
-        ComponentType.role_select,
-        ComponentType.channel_select,
-        ComponentType.mentionable_select,
-    ],
+    defaults: Sequence[ValidDefaultValues], component_type: DefaultSelectComponentTypes
 ) -> List[SelectDefaultValue]:
     if not defaults or defaults is MISSING:
         return []
@@ -128,6 +139,7 @@ def _handle_select_defaults(
     cls_to_type: Dict[Type[ValidDefaultValues], SelectDefaultValueType] = {
         User: SelectDefaultValueType.user,
         Member: SelectDefaultValueType.user,
+        ClientUser: SelectDefaultValueType.user,
         Role: SelectDefaultValueType.role,
         GuildChannel: SelectDefaultValueType.channel,
         AppCommandChannel: SelectDefaultValueType.channel,
@@ -135,10 +147,10 @@ def _handle_select_defaults(
         Thread: SelectDefaultValueType.channel,
     }
     type_to_supported_classes: Dict[ValidSelectType, Tuple[Type[ValidDefaultValues], ...]] = {
-        ComponentType.user_select: (User, Member, Object),
+        ComponentType.user_select: (User, ClientUser, Member, Object),
         ComponentType.role_select: (Role, Object),
         ComponentType.channel_select: (GuildChannel, AppCommandChannel, AppCommandThread, Thread, Object),
-        ComponentType.mentionable_select: (User, Member, Role, Object),
+        ComponentType.mentionable_select: (User, ClientUser, Member, Role, Object),
     }
 
     values: List[SelectDefaultValue] = []
@@ -149,7 +161,7 @@ def _handle_select_defaults(
 
         object_type = obj.__class__ if not isinstance(obj, Object) else obj.type
 
-        if object_type not in type_to_supported_classes[component_type]:
+        if not _is_valid_object_type(object_type, component_type, type_to_supported_classes):
             # TODO: split this into a util function
             supported_classes = [c.__name__ for c in type_to_supported_classes[component_type]]
             if len(supported_classes) > 2:
@@ -173,6 +185,9 @@ def _handle_select_defaults(
             elif component_type is ComponentType.channel_select:
                 object_type = GuildChannel
 
+        if issubclass(object_type, GuildChannel):
+            object_type = GuildChannel
+
         values.append(SelectDefaultValue(id=obj.id, type=cls_to_type[object_type]))
 
     return values