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asyncio.shutdown_asyncgens silently drops CancelledError from generator cleanup #150866
Description
Bug report
Bug description:
asyncio.BaseEventLoop.shutdown_asyncgens silently swallows CancelledError raised during asynchronous generator cleanup:
# Lib/asyncio/base_events.py:592-599
for result, agen in zip(results, closing_agens):
if isinstance(result, Exception):
self.call_exception_handler({
'message': f'an error occurred during closing of '
f'asynchronous generator {agen!r}',
'exception': result,
'asyncgen': agen
})CancelledError that can be raised by the aclose() is not inherited from the Exception, it inherits from BaseException.
Reproducer:
import asyncio
async def agen():
try:
yield 1
finally:
raise asyncio.CancelledError("cancelled during cleanup")
caught = []
async def main():
loop = asyncio.get_running_loop()
loop.set_exception_handler(lambda loop, ctx: caught.append(ctx))
g = agen()
await g.__anext__()
await loop.shutdown_asyncgens()
asyncio.run(main())
assert len(caught) == 1, f"Expected 1 handler call, got {len(caught)}"Proposed fix:
Match both Exception and CancelledError
if isinstance(result, (Exception, asyncio.CancelledError)):CPython versions tested on:
3.16, CPython main branch
Operating systems tested on:
macOS
Activity
deadlovelll commentedon Jun 3, 2026
I'll create the pr
kumaraditya303 commentedon Jul 24, 2026
What about other base exceptions like SystemExit? I think currently they would be dropped as well.
deadlovelll commentedon Jul 25, 2026
exceptions like SystemExit do not reach this point because they reraise instead of storing it, but your direction is right, and I'll switch to isinstance(result, BaseException)
gh-150866: Fix asyncio shutdown_asyncgens to report BaseException (#1…
pythongh-150866: Fix asyncio shutdown_asyncgens to report BaseExcepti…