Change autocomplete callbacks to only take two parameters

The old namespace parameter can be retrieved using the
Interaction.namespace property instead, which leads to somewhat cleaner
code.

discord/app_commands/commands.py

@@ -112,8 +112,8 @@ if TYPE_CHECKING:
     ]
 
     AutocompleteCallback = Union[
-        Callable[[GroupT, 'Interaction', ChoiceT, Namespace], Coro[List[Choice[ChoiceT]]]],
+        Callable[[GroupT, 'Interaction', ChoiceT], Coro[List[Choice[ChoiceT]]]],
-        Callable[['Interaction', ChoiceT, Namespace], Coro[List[Choice[ChoiceT]]]],
+        Callable[['Interaction', ChoiceT], Coro[List[Choice[ChoiceT]]]],
     ]
 else:
     CommandCallback = Callable[..., Coro[T]]
@@ -163,11 +163,11 @@ def _validate_auto_complete_callback(
 ) -> AutocompleteCallback[GroupT, ChoiceT]:
 
     requires_binding = is_inside_class(callback)
-    required_parameters = 3 + requires_binding
+    required_parameters = 2 + requires_binding
     callback.requires_binding = requires_binding
     params = inspect.signature(callback).parameters
-    if len(params) < required_parameters:
+    if len(params) != required_parameters:
-        raise TypeError('autocomplete callback requires either 3 or 4 parameters to be passed')
+        raise TypeError('autocomplete callback requires either 2 or 3 parameters to be passed')
 
     return callback
 
@@ -493,11 +493,11 @@ class Command(Generic[GroupT, P, T]):
 
         if param.autocomplete.requires_binding:
             if self.binding is not None:
-                choices = await param.autocomplete(self.binding, interaction, value, namespace)
+                choices = await param.autocomplete(self.binding, interaction, value)
             else:
                 raise TypeError('autocomplete parameter expected a bound self parameter but one was not provided')
         else:
-            choices = await param.autocomplete(interaction, value, namespace)
+            choices = await param.autocomplete(interaction, value)
 
         if interaction.response.is_done():
             return
@@ -546,10 +546,13 @@ class Command(Generic[GroupT, P, T]):
     ) -> Callable[[AutocompleteCallback[GroupT, ChoiceT]], AutocompleteCallback[GroupT, ChoiceT]]:
         """A decorator that registers a coroutine as an autocomplete prompt for a parameter.
 
-        The coroutine callback must have 3 parameters, the :class:`~discord.Interaction`,
+        The coroutine callback must have 2 parameters, the :class:`~discord.Interaction`,
-        the current value by the user (usually either a :class:`str`, :class:`int`, or :class:`float`,
+        and the current value by the user (usually either a :class:`str`, :class:`int`, or :class:`float`,
-        depending on the type of the parameter being marked as autocomplete), and then the
+        depending on the type of the parameter being marked as autocomplete).
-        :class:`Namespace` that represents possible values are partially filled in.
+
+        To get the values from other parameters that may be filled in, accessing
+        :attr:`.Interaction.namespace` will give a :class:`Namespace` object with those
+        values.
 
         The coroutine decorator **must** return a list of :class:`~discord.app_commands.Choice` objects.
         Only up to 25 objects are supported.
@@ -566,7 +569,6 @@ class Command(Generic[GroupT, P, T]):
             async def fruits_autocomplete(
                 interaction: discord.Interaction,
                 current: str,
-                namespace: app_commands.Namespace
             ) -> List[app_commands.Choice[str]]:
                 fruits = ['Banana', 'Pineapple', 'Apple', 'Watermelon', 'Melon', 'Cherry']
                 return [
@@ -1163,6 +1165,8 @@ def autocomplete(**parameters: AutocompleteCallback[GroupT, ChoiceT]) -> Callabl
     Autocomplete is only supported on types that have :class:`str`, :class:`int`, or :class:`float`
     values.
 
+    For more information, see the :meth:`Command.autocomplete` documentation.
+
     Example:
 
     .. code-block:: python3
@@ -1175,7 +1179,6 @@ def autocomplete(**parameters: AutocompleteCallback[GroupT, ChoiceT]) -> Callabl
             async def fruits_autocomplete(
                 interaction: discord.Interaction,
                 current: str,
-                namespace: app_commands.Namespace
             ) -> List[app_commands.Choice[str]]:
                 fruits = ['Banana', 'Pineapple', 'Apple', 'Watermelon', 'Melon', 'Cherry']
                 return [