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create_task(name=...) silently fails to set name with custom task_factory after gh-128308 #132593
Description
Bug report
Bug description:
During a rebuild of all packages in Debian unstable, the uvloop test suite failed due to a new behavior in asyncio.
This suite runs each test twice: once with uvloop implementation (which passes) and once with Python’s asyncio implementation (which fails).
Since
Commit: 38a99568763604ccec5d5027f0658100ad76876f
PR: https://github.com/python/cpython/pull/128768
asyncio.BaseEventLoop.create_task() no longer calls set_name(name). This breaks compatibility with any factory that does not set the name manually.
Expected behavior
When using create_task(..., name="example name"), the task's name should always be set - even when using a custom task factory - as it was before the regression.
Actual behavior
With a custom factory that returns a subclassed asyncio.Task, the task name is None unless the factory manually calls set_name(name). This is a silent behavioral change that breaks code relying on set_name() being called by the event loop.
My Environment
Python version: 3.13.2
Debian testing
Script to reproduce
import asyncio
async def main():
names = []
async def get_name():
names.append(asyncio.current_task().get_name())
async with asyncio.TaskGroup() as tg:
tg.create_task(get_name(), name="example name")
print(names)
asyncio.run(main()) # Output: ['example name']
def factory():
loop = asyncio.new_event_loop()
loop.set_task_factory(asyncio.eager_task_factory)
return loop
asyncio.run(main(), loop_factory=factory) # Output: ['example name']
# Fails silently with custom task_factory
result = None
class MyTask(asyncio.Task):
def set_name(self, name):
global result
print(name) # never reached
result = name + "!"
def get_name(self):
global result
return result
def loop_factory():
loop = asyncio.new_event_loop()
loop.set_task_factory(asyncio.create_eager_task_factory(MyTask))
return loop
asyncio.run(main(), loop_factory=loop_factory) # Output: ['None']CPython versions tested on:
3.13
Operating systems tested on:
Linux
Activity
kthreadd commentedon Apr 17, 2025
Hi @sergiosacj
Yes, from #128308 on, the
asyncio.BaseEventLoop.create_task()no longer callsset_name().The name setting operation is actually done in the C function during calling
create_task(..., name="example name"), not set by `set_name.And by the way, from the code you supplied, the function
get_nameoverwritten byMyTask, so it seems that it's the reason whynames.append(asyncio.current_task().get_name())getsNone.So, you could get correct name
example nameif you have a correctget_name, even you didn't set name manually viaset_name(), because the name will be set by callingcreate_task(..., name="example name").sergiosacj commentedon Apr 17, 2025
Thanks @kthreadd, I misinterpreted then.
When I read the documentation, I thought set_name should be called in this scenario. Maybe the sentence below should be updated?
"If name is not None, it is set as the name of the task using Task.set_name()"
That's right, this code assumed that set_name was called inside create_task. I made this example based on this test here.
kthreadd commentedon Apr 17, 2025
@sergiosacj, ok, I also noticed that the out of date description in document asyncio.create_task, for the same, test case is also out of date test_set_task_name
Both of them need to be updated I believe.
picnixz commentedon May 9, 2025
We tracked the more general issue in #133745.