New submission from Devin Fee :
I expected an async-generator's aclose() method to cancel it's __anext__().
Instead, the task isn't cancelled, and (it seems) manually cleanup is necessary.
@pytest.mark.asyncio
async def test_aclose_cancels():
done = False
event = asyncio.Event()
agen = None
async def make_agen():
try:
await event.wait()
raise NotImplementedError()
yield # pylint: disable=W0101, unreachable
finally:
nonlocal done
done = True
async def run():
nonlocal agen
agen = make_agen()
await agen.__anext__()
task = asyncio.ensure_future(run())
await asyncio.sleep(.01)
await agen.aclose()
await asyncio.sleep(.01)
assert done
assert task.done() and task.exception()
Looking at the tests for CPython, the implementation seems to expect it, but
I'm unclear if PEP-525 actually intends for this to be the case:
https://github.com/python/cpython/blob/e42b705188271da108de42b55d9344642170aa2b/Lib/test/test_asyncgen.py#L657
Alternatively, maybe I shouldn't be calling aclose, and instead I should be
cancelling the task:
@pytest.mark.asyncio
async def test_cancel_finalizes():
done = False
event = asyncio.Event()
agen = None
async def make_agen():
try:
await event.wait()
raise NotImplementedError()
yield # pylint: disable=W0101, unreachable
finally:
nonlocal done
done = True
async def run():
nonlocal agen
agen = make_agen()
await agen.__anext__()
task = asyncio.ensure_future(run())
await asyncio.sleep(.01)
task.cancel()
await asyncio.sleep(.01)
assert done
assert task.done()
So the "bug" here is one of PEP-525 clarification.
--
components: asyncio
messages: 325699
nosy: asvetlov, dfee, yselivanov
priority: normal
severity: normal
status: open
title: aclose() doesn't stop raise StopAsyncIteration / GeneratorExit to
__anext__()
versions: Python 3.7
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<https://bugs.python.org/issue34730>
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