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asyncio.gather() leaves stale awaited_by links when argument validation fails #161083
Description
Bug report
A failed asyncio.gather() call can leave stale task nodes
Repro:
import asyncio
async def main():
task = asyncio.create_task(asyncio.sleep(0))
try:
result = await asyncio.gather(task, None)
except TypeError as e:
pass
asyncio.print_call_graph(task)
await task
asyncio.run(main())The problem here is that you can't pass None to gather(), it raises TypeError, so nobody awaits task.
Actual:
* Task(name='Task-2', id=0x1038c07d0)
+ Call stack:
| File '/Users/timofeiivankov/cpython/Lib/asyncio/tasks.py', line 718, in async sleep()
+ Awaited by:
* Task(name='Task-1', id=0x1038c05f0)
+ Call stack:
| File '/Users/timofeiivankov/cpython/repro.py', line 10, in async main()
Expected:
* Task(name='Task-2', id=0x10306c9b0)
+ Call stack:
| File '/Users/timofeiivankov/cpython/Lib/asyncio/tasks.py', line 718, in async sleep()
Proposed fix: register task nodes only after all gather() arguments have been successfully processed.
I'm gonna work on a fix for this
CPython versions tested on:
CPython main branch
Operating systems tested on:
macOS
Activity
picnixz commentedon Nov 1, 2026
deadlovelll commentedon Nov 1, 2026
picnixz commentedon Nov 1, 2026
kumaraditya303 commentedon Nov 2, 2026
I'll review this one but I don't encourage working on such issues which no one would hit in real world.
deadlovelll commentedon Nov 2, 2026
Thanks, i'll keep in mind for the future issues