[commands module] functools.partial support (#3542)

* No reason we can't support this

* meh

* there we go...

redbot/core/commands/commands.py

@@ -7,13 +7,11 @@ from __future__ import annotations
 
 import inspect
 import re
+import functools
 import weakref
 from typing import (
     Awaitable,
     Callable,
-    Coroutine,
-    TypeVar,
-    Type,
     Dict,
     List,
     Optional,
@@ -21,7 +19,6 @@ from typing import (
     Union,
     MutableMapping,
     TYPE_CHECKING,
-    cast,
 )
 
 import discord
@@ -38,7 +35,6 @@ from discord.ext.commands import (
     Greedy,
 )
 
-from . import converter as converters
 from .errors import ConversionFailure
 from .requires import PermState, PrivilegeLevel, Requires, PermStateAllowedStates
 from ..i18n import Translator
@@ -307,11 +303,19 @@ class Command(CogCommandMixin, DPYCommand):
     def callback(self, function):
         """
         Below should be mostly the same as discord.py
-        The only (current) change is to filter out typing.Optional
-        if a user has specified the desire for this behavior
+
+        Currently, we modify behavior for
+
+          - functools.partial support
+          - typing.Optional behavior change as an option
         """
         self._callback = function
+        if isinstance(function, functools.partial):
+            self.module = function.func.__module__
+            globals_ = function.func.__globals__
+        else:
             self.module = function.__module__
+            globals_ = function.__globals__
 
         signature = inspect.signature(function)
         self.params = signature.parameters.copy()
@@ -322,7 +326,7 @@ class Command(CogCommandMixin, DPYCommand):
         for key, value in self.params.items():
             if isinstance(value.annotation, str):
                 self.params[key] = value = value.replace(
-                    annotation=eval(value.annotation, function.__globals__)
+                    annotation=eval(value.annotation, globals_)
                 )
 
             # fail early for when someone passes an unparameterized Greedy type