In 3.13.* if custom asyncio task factory is set and no task name is provided to asyncio.create_task, task name provided by task factory is overwritten to "None".

[axzxc1236]

Bug report

Bug description:

Code below illustrate a behavior change in 3.13 which I believe is a bug, which "Task-2" the task name becomes "None" while calling asyncio.current_task().get_name()

import asyncio

def task_factory(loop, *args, **kwargs):
    new_task = asyncio.Task(*args, **kwargs)
    name = new_task.get_name()
    # Python 3.9 to 3.13 prints name='Task-2'
    # 'Task-3' and 'Task-4' is also printed because loop is shutting down, which is not in the scope of (possible) bug
    print(f"{name=}")
    return new_task

async def print_task_name():
    current_task = asyncio.current_task()
    name = current_task.get_name()
    # Python 3.13 prints name='None' (but why does it print 'Task-2' before it's returned from task_factory() ?)
    # Python 3.9 to 3.12 prints name='Task-2'
    print(f"{name=}")

async def main():
    loop = asyncio.get_running_loop()
    loop.set_task_factory(task_factory)
    new_task = asyncio.create_task(print_task_name())
    await new_task

asyncio.run(main())

The source of bug/behavior change is that https://github.com/python/cpython/blob/v3.13.2/Lib/asyncio/base_events.py#L478 a set_name() is called unconditionally and version before 3.13 (e.g. https://github.com/python/cpython/blob/v3.12.9/Lib/asyncio/tasks.py#L70 ) setting task name to None does nothing which avoided the issue with custom task factory setting it's own task name.

If using a task factory, the task name can't be generated by task factory because it gets rewritten to name provided by asyncio.create_task(), which I think most people doesn't provide one.

Suggestion: check if name parameter is None before overwriting task name in create_task(), otherwise keep task name generated by task factory, and probably pass "name" parameter to task factory.

CPython versions tested on:

3.13

Operating systems tested on:

Linux

[asvetlov]

Agree, loop.create_task() should call set_name() only if the name is not None.
The bug exists in 3.13 only, the main branch has a different code and it should work fine.

[gvanrossum]

Worth making a 3.13-specific fix though, right?

[asvetlov]

I'll do it

[asvetlov]

I think if we backport #128308, the fix covers the bug report well.

[asvetlov]

The backport #130084 is ready for review.

[asvetlov]

The fix was merged into the 3.13 branch.