Improve typing of app command transformers

This allows subclasses of transformers to specify a specialization for
interaction without violating covariance of parameter types

discord/app_commands/transformers.py

@@ -34,6 +34,7 @@ from typing import (
     ClassVar,
     Coroutine,
     Dict,
+    Generic,
     List,
     Literal,
     Optional,
@@ -56,6 +57,7 @@ from ..user import User
 from ..role import Role
 from ..member import Member
 from ..message import Attachment
+from .._types import ClientT
 
 __all__ = (
     'Transformer',
@@ -191,7 +193,7 @@ class CommandParameter:
         return self.name if self._rename is MISSING else str(self._rename)
 
 
-class Transformer:
+class Transformer(Generic[ClientT]):
     """The base class that allows a type annotation in an application command parameter
     to map into a :class:`~discord.AppCommandOptionType` and transform the raw value into one
     from this type.
@@ -304,7 +306,7 @@ class Transformer:
         else:
             return name
 
-    async def transform(self, interaction: Interaction, value: Any, /) -> Any:
+    async def transform(self, interaction: Interaction[ClientT], value: Any, /) -> Any:
         """|maybecoro|
 
         Transforms the converted option value into another value.
@@ -324,7 +326,7 @@ class Transformer:
         raise NotImplementedError('Derived classes need to implement this.')
 
     async def autocomplete(
-        self, interaction: Interaction, value: Union[int, float, str], /
+        self, interaction: Interaction[ClientT], value: Union[int, float, str], /
     ) -> List[Choice[Union[int, float, str]]]:
         """|coro|
 
@@ -352,7 +354,7 @@ class Transformer:
         raise NotImplementedError('Derived classes can implement this.')
 
 
-class IdentityTransformer(Transformer):
+class IdentityTransformer(Transformer[ClientT]):
     def __init__(self, type: AppCommandOptionType) -> None:
         self._type = type
 
@@ -360,7 +362,7 @@ class IdentityTransformer(Transformer):
     def type(self) -> AppCommandOptionType:
         return self._type
 
-    async def transform(self, interaction: Interaction, value: Any, /) -> Any:
+    async def transform(self, interaction: Interaction[ClientT], value: Any, /) -> Any:
         return value
 
 
@@ -489,7 +491,7 @@ class EnumNameTransformer(Transformer):
         return self._enum[value]
 
 
-class InlineTransformer(Transformer):
+class InlineTransformer(Transformer[ClientT]):
     def __init__(self, annotation: Any) -> None:
         super().__init__()
         self.annotation: Any = annotation
@@ -502,7 +504,7 @@ class InlineTransformer(Transformer):
     def type(self) -> AppCommandOptionType:
         return AppCommandOptionType.string
 
-    async def transform(self, interaction: Interaction, value: Any, /) -> Any:
+    async def transform(self, interaction: Interaction[ClientT], value: Any, /) -> Any:
         return await self.annotation.transform(interaction, value)
 
 
@@ -611,18 +613,18 @@ else:
             return transformer
 
 
-class MemberTransformer(Transformer):
+class MemberTransformer(Transformer[ClientT]):
     @property
     def type(self) -> AppCommandOptionType:
         return AppCommandOptionType.user
 
-    async def transform(self, interaction: Interaction, value: Any, /) -> Member:
+    async def transform(self, interaction: Interaction[ClientT], value: Any, /) -> Member:
         if not isinstance(value, Member):
             raise TransformerError(value, self.type, self)
         return value
 
 
-class BaseChannelTransformer(Transformer):
+class BaseChannelTransformer(Transformer[ClientT]):
     def __init__(self, *channel_types: Type[Any]) -> None:
         super().__init__()
         if len(channel_types) == 1:
@@ -654,22 +656,22 @@ class BaseChannelTransformer(Transformer):
     def channel_types(self) -> List[ChannelType]:
         return self._channel_types
 
-    async def transform(self, interaction: Interaction, value: Any, /):
+    async def transform(self, interaction: Interaction[ClientT], value: Any, /):
         resolved = value.resolve()
         if resolved is None or not isinstance(resolved, self._types):
             raise TransformerError(value, AppCommandOptionType.channel, self)
         return resolved
 
 
-class RawChannelTransformer(BaseChannelTransformer):
-    async def transform(self, interaction: Interaction, value: Any, /):
+class RawChannelTransformer(BaseChannelTransformer[ClientT]):
+    async def transform(self, interaction: Interaction[ClientT], value: Any, /):
         if not isinstance(value, self._types):
             raise TransformerError(value, AppCommandOptionType.channel, self)
         return value
 
 
-class UnionChannelTransformer(BaseChannelTransformer):
-    async def transform(self, interaction: Interaction, value: Any, /):
+class UnionChannelTransformer(BaseChannelTransformer[ClientT]):
+    async def transform(self, interaction: Interaction[ClientT], value: Any, /):
         if isinstance(value, self._types):
             return value