TypeError: create_task() got an unexpected keyword argument 'eager_start'

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
48/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Quiet
Tech stack
python
Domain
backend

Research direction

Start at uvloop.loop.Loop.create_task in loop.pyx, where the traceback shows Python 3.14's eager_start keyword is rejected, and compare it with asyncio.create_task's behavior. Determine how uvloop should accept and respect eager_start=True without merely ignoring it; done means the reported call works under uvloop with the intended eager-start semantics.

Written by the indexing model from the issue text.

Description

python 3.14.2 asyncio.create_task() accepts a kwarg eager_start: True. uvloop 0.22.1 does not and raises a type error:

  File "/Users/enda/Workspaces/project/api/src/prject/queries/counts.py", line 84, in _single_flight
    task = asyncio.create_task(_run(), name=f"single_flight:{key}", eager_start=True)
  File "/Users/enda/.local/share/uv/python/cpython-3.14.2-macos-aarch64-none/lib/python3.14/asyncio/tasks.py", line 395, in create_task
    return loop.create_task(coro, **kwargs)
           ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^
  File "uvloop/loop.pyx", line 1415, in uvloop.loop.Loop.create_task
TypeError: create_task() got an unexpected keyword argument 'eager_start'

I understand that "accept but ignore-with-a-warning" is not a desirable approach as developers will expect that passing this in as True will cause the task to start eagerly. However, at present the first sentence of the project "uvloop is a fast, drop-in replacement of the built-in asyncio event loop. " is no longer100% accurate and that's not desired either.

I've only recently become aware of eager_start but it /seems/ to have been in discussion for over 18 months: https://discuss.python.org/t/make-asyncio-eager-task-factory-default/75164 (and uvloop gets a mention in there).

As I don't know what is involved in accepting and respecting an eager_start=True I don't want to say what I expect this issue to amount to, but it made its way pasting our testing as we were not using uvloop in the original tests which covered our _single_flight code, but our deployed code hit it. Clearly we have now fixed that testing oversite but others may experience this too.

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