[tasks] support defining tasks on a slotted class

[SebbyLaw]

Summary

support defining tasks on a slotted class.

Before:

import asyncio
from discord.ext import tasks

class MyClass:
    __slots__ = ("foo", "bar")

    def __init__(self):
        self.foo = "Hello"
        self.bar = "World!"

    @tasks.loop(seconds=5.0)
    async def baz(self):
        print(self.foo, self.bar)

async def main():
    a = MyClass()
    a.baz.start()  # error

    await asyncio.sleep(float("inf"))

if __name__ == "__main__":
    asyncio.run(main())

Traceback (most recent call last):
  File "/home/sebnlaw/discord.py/_test.py", line 25, in <module>
    asyncio.run(main())
  File "/home/sebnlaw/miniconda3/lib/python3.10/asyncio/runners.py", line 44, in run
    return loop.run_until_complete(main)
  File "/home/sebnlaw/miniconda3/lib/python3.10/asyncio/base_events.py", line 649, in run_until_complete
    return future.result()
  File "/home/sebnlaw/discord.py/_test.py", line 19, in main
    a.baz.start()
  File "/home/sebnlaw/discord.py/discord/ext/tasks/__init__.py", line 293, in __get__
    setattr(obj, self.coro.__name__, copy)
AttributeError: 'MyClass' object attribute 'baz' is read-only. Did you mean: 'bar'?

After:

import asyncio
from discord.ext import tasks

class MyClass:
    __slots__ = ("foo", "bar", "_cs_baz")

    def __init__(self):
        self.foo = "Hello"
        self.bar = "World!"

    @tasks.loop(seconds=5.0, slot_name="_cs_baz")
    async def baz(self):
        print(self.foo, self.bar)

async def main():
    a = MyClass()
    a.baz.start()  # yippee

    await asyncio.sleep(float("inf"))

if __name__ == "__main__":
    asyncio.run(main())

Checklist

• If code changes were made then they have been tested.
  • I have updated the documentation to reflect the changes.
• This PR fixes an issue.
• This PR adds something new (e.g. new method or parameters).
• This PR is a breaking change (e.g. methods or parameters removed/renamed)
• This PR is not a code change (e.g. documentation, README, ...)

[Rapptz]

Thanks for the PR.

I don't really see much point in this one though. If you're making a slotted class which is meant for classes that have thousands of instances then I don't see why you'd have a task associated with each of those instances. Aside from that, you can always just add e.g. baz to the __slots__ list yourself and have it work as-is.

[SebbyLaw]

Aside from that, you can always just add e.g. baz to the __slots__ list yourself and have it work as-is.

You cannot.

import asyncio
from discord.ext import tasks

class MyClass:
    __slots__ = ("foo", "bar", "baz")

    def __init__(self):
        self.foo = "Hello"
        self.bar = "World!"

    @tasks.loop(seconds=5.0)
    async def baz(self):
        print(self.foo, self.bar)

async def main():
    a = MyClass()
    a.baz.start()  # error

    await asyncio.sleep(float("inf"))

if __name__ == "__main__":
    asyncio.run(main())

Traceback (most recent call last):
  File "/home/sebnlaw/discord.py/_test.py", line 5, in <module>
    class MyClass:
ValueError: 'baz' in __slots__ conflicts with class variable

[Rapptz]

Ah right, it fails to create the slot descriptor if it's a class variable. My mistake. I still don't get the point of doing this on a slotted class though.