Make asyncio.isfuture a TypeGuard
#7057
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stdlib/asyncio/base_futures.pyi
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| _FINISHED: Literal["FINISHED"] # undocumented | ||
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| def isfuture(obj: object) -> bool: ... | ||
| def isfuture(obj: object) -> TypeGuard[futures.Future]: ... |
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At runtime this allows any object with a specific attribute:
return (hasattr(obj.__class__, '_asyncio_future_blocking') and
obj._asyncio_future_blocking is not None)
I don't think that's enough for a TypeGuard.
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The docs put it this way:
https://docs.python.org/3/library/asyncio-future.html#asyncio.isfuture
a Future-like object with a _asyncio_future_blocking attribute.
# - Its presence is a marker to declare that a class implements # the Future protocol (i.e. is intended to be duck-type compatible). # The value must also be not-None, to enable a subclass to declare # that it is not compatible by setting this to None.
In my opinion, this is enough to be a TypeGuard
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The doc regarding _asyncio_future_blocking is correct.
I have another question. asyncio.Future is a generic type.
Should the typeguard reflect it, annotating at least Future[Any]?
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According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉 |
asvetlov
approved these changes
Jan 28, 2022
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Docs https://docs.python.org/3/library/asyncio-future.html#asyncio.isfuture