Command parameters broken for callbacks in closures

[scottanderson42]

Summary

A slash command callback in a closure is treated as a class member

Reproduction Steps

1. Create a closure with a command defined it it by either a decorator or add_application_command.
2. Call the closure during bot startup.
3. The command will fail because it assumes non-module-level functions are class methods.

Minimal Reproducible Code

import discord  # For great justice !!
client = discord.Bot()

def prepare_command(some_arg: str) -> discord.SlashCommand:
    async def rhubarb(
            ctx,
            command: discord.Option(str, "The thing to do, yo."),
            args: discord.Option(str, "The things to do it to, yo."),
    ):
        print("/rhubarb", command)

    slash_command = discord.SlashCommand(
        rhubarb,
        name="rhubarb",
        description="Do wanton acts with toes.",
        options=[
            discord.Option(str, name="command"),
            discord.Option(str, name="args"),
        ]
    )
    client.add_application_command(slash_command)

prepare_command("parsnips")

client.run("etcetcetc")

Expected Results

The command to be registered with the application.

Actually I also expected to win a complimentary vacation to Fargo, Minnesota as well, but I suspect there might be other issues with my code as well...

Actual Results

Traceback (most recent call last):
  File "/root/.cache/pypoetry/virtualenvs/rhubarb-9wL-Y1vf-py3.9/lib/python3.9/site-packages/discord/commands/core.py", line 737, in _match_option_param_names
    p_name, p_obj = next(params)
StopIteration

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/opt/lib/python/rhubarb/startup.py", line 60, in <module>
    asyncio.run(bot.start_bot())
  File "/opt/lib/python/rhubarb/discord/bot.py", line 109, in start_bot
    rhubarb.prepare_command("parsnips")
  File "/opt/lib/python/rhubarb/discord/commands/rhubarb.py", line 27, in prepare_command
    slash_command = discord.SlashCommand(
  File "/root/.cache/pypoetry/virtualenvs/rhubarb-9wL-Y1vf-py3.9/lib/python3.9/site-packages/discord/commands/core.py", line 644, in __init__
    self.options: List[Option] = self._match_option_param_names(params, kwop)
  File "/root/.cache/pypoetry/virtualenvs/rhubarb-9wL-Y1vf-py3.9/lib/python3.9/site-packages/discord/commands/core.py", line 740, in _match_option_param_names
    raise ClientException("Too many arguments passed to the options kwarg.")
discord.errors.ClientException: Too many arguments passed to the options kwarg.

Intents

Defaults.

System Information

• Python v3.9.7-final
• py-cord v2.0.0-final
• aiohttp v3.8.1
• system info: Linux 5.10.104-linuxkit Update README.rst #1 SMP PREEMPT Thu Mar 17 17:05:54 UTC 2022

Checklist

• I have searched the open issues for duplicates.
• I have shown the entire traceback, if possible.
• I have removed my token from display, if visible.

Additional Context

The problem lies in _check_required_params:

    def _check_required_params(self, params):
        params = iter(params.items())
        required_params = (
            ["self", "context"]
            if self.attached_to_group
            or self.cog
            or len(self.callback.__qualname__.split(".")) > 1  # <--- here be ye olde scallawag
            else ["context"]
        )

In a closure, the callback function's __qualname__ looks like this:

prepare_command.<locals>.rhubarb

And so the code assumes that it is a class instance method, meaning that it will be passed self as the first argument. The required params have one too many params, the first option parameter gets swallowed in _match_option_param_names as a result, and Bob's your uncle, stack trace ahoy!

Using a static class method for a callback probably has the same issue (because they receive neither self nor cls as their first parameter) but I have not tested that.

[Middledot]

Seems to have already been fixed in #1589