[commands] Properly support commands.param in hybrid commands

discord/ext/commands/hybrid.py

@@ -42,8 +42,9 @@ import inspect
 from discord import app_commands
 from discord.utils import MISSING, maybe_coroutine, async_all
 from .core import Command, Group
-from .errors import CommandRegistrationError, CommandError, HybridCommandError, ConversionError
+from .errors import BadArgument, CommandRegistrationError, CommandError, HybridCommandError, ConversionError
 from .converter import Converter
+from .parameters import Parameter
 from .cog import Cog
 
 if TYPE_CHECKING:
@@ -51,7 +52,6 @@ if TYPE_CHECKING:
     from ._types import ContextT, Coro, BotT
     from .bot import Bot
     from .context import Context
-    from .parameters import Parameter
     from discord.app_commands.commands import (
         Check as AppCommandCheck,
         AutocompleteCallback,
@@ -71,6 +71,7 @@ CogT = TypeVar('CogT', bound='Cog')
 CommandT = TypeVar('CommandT', bound='Command')
 # CHT = TypeVar('CHT', bound='Check')
 GroupT = TypeVar('GroupT', bound='Group')
+_NoneType = type(None)
 
 if TYPE_CHECKING:
     P = ParamSpec('P')
@@ -85,6 +86,17 @@ else:
     P2 = TypeVar('P2')
 
 
+class _CallableDefault:
+    __slots__ = ('func',)
+
+    def __init__(self, func: Callable[[Context], Any]) -> None:
+        self.func: Callable[[Context], Any] = func
+
+    @property
+    def __class__(self) -> Any:
+        return _NoneType
+
+
 def is_converter(converter: Any) -> bool:
     return (inspect.isclass(converter) and issubclass(converter, Converter)) or isinstance(converter, Converter)
 
@@ -107,12 +119,33 @@ def make_converter_transformer(converter: Any) -> Type[app_commands.Transformer]
     return type('ConverterTransformer', (app_commands.Transformer,), {'transform': classmethod(transform)})
 
 
+def make_callable_transformer(func: Callable[[str], Any]) -> Type[app_commands.Transformer]:
+    async def transform(cls, interaction: discord.Interaction, value: str) -> Any:
+        try:
+            return func(value)
+        except CommandError:
+            raise
+        except Exception as exc:
+            raise BadArgument(f'Converting to "{func.__name__}" failed') from exc
+
+    return type('CallableTransformer', (app_commands.Transformer,), {'transform': classmethod(transform)})
+
+
 def replace_parameters(parameters: Dict[str, Parameter], signature: inspect.Signature) -> List[inspect.Parameter]:
     # Need to convert commands.Parameter back to inspect.Parameter so this will be a bit ugly
     params = signature.parameters.copy()
     for name, parameter in parameters.items():
-        if is_converter(parameter.converter) and not hasattr(parameter.converter, '__discord_app_commands_transformer__'):
+        is_transformer = hasattr(parameter.converter, '__discord_app_commands_transformer__')
+        if is_converter(parameter.converter) and not is_transformer:
             params[name] = params[name].replace(annotation=make_converter_transformer(parameter.converter))
+        if callable(parameter.converter) and not inspect.isclass(parameter.converter) and not is_transformer:
+            params[name] = params[name].replace(annotation=make_callable_transformer(parameter.converter))
+        if callable(parameter.default):
+            params[name] = params[name].replace(default=_CallableDefault(parameter.default))
+
+        if isinstance(params[name].default, Parameter):
+            # If we're here, then then it hasn't been handled yet so it should be removed completely
+            params[name] = params[name].replace(default=parameter.empty)
 
     return list(params.values())
 
@@ -146,6 +179,28 @@ class HybridAppCommand(discord.app_commands.Command[CogT, P, T]):
         }
         return self._copy_with(parent=self.parent, binding=self.binding, bindings=bindings)
 
+    async def _transform_arguments(
+        self, interaction: discord.Interaction, namespace: app_commands.Namespace
+    ) -> Dict[str, Any]:
+        values = namespace.__dict__
+        transformed_values = {}
+
+        for param in self._params.values():
+            try:
+                value = values[param.display_name]
+            except KeyError:
+                if not param.required:
+                    if isinstance(param.default, _CallableDefault):
+                        transformed_values[param.name] = await maybe_coroutine(param.default.func, interaction._baton)
+                    else:
+                        transformed_values[param.name] = param.default
+                else:
+                    raise app_commands.CommandSignatureMismatch(self) from None
+            else:
+                transformed_values[param.name] = await param.transform(interaction, value)
+
+        return transformed_values
+
     async def _check_can_run(self, interaction: discord.Interaction) -> bool:
         # Hybrid checks must run like so:
         # - Bot global check once