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asvetlov commented Dec 9, 2019

* ``with (await asyncio.lock):`` and ``with (yield from asyncio.lock):`` statements are
not longer supported, use ``async with lock`` instead. The same is correct for
``asyncio.Condition`` and ``asyncio.Semaphore``.
(Contributed by Andrew Svetlov in :issue:`34793`.)
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Please also replace the deprecation warning with changedversion in https://docs.python.org/3/library/asyncio-sync.html#boundedsemaphore

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Done

class _ContextManagerMixin:
def __enter__(self):
raise RuntimeError(
'"yield from" should be used as context manager expression')
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Should we keep this? We can change the error message to say that async with should be used...

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I think the motivation was emphasizing that context managers were supported but in a slightly unusual way: with (yield from lock):; bare with lock: was forbidden.

After switching to async with lock: everything becomes clear: with is not supported in any form for the sake of async with. The error message is standard and well-known: AttributeError: __enter__. I think we shouldn't replace the default behavior.

Maybe the standard text can be improved globally, but it is another story, I guess.

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4 participants