[Python-Dev] Concurrent.futures: no type discovery for PyCharm

Ilya Kamenshchikov ikamenshchikov at gmail.com
Tue Apr 23 15:32:22 EDT 2019


How would we answer the same question if it was not a part of stdlib?
I am not sure it is fair to expect of Pycharm to parse / execute the
__getattr__ on modules, as more elaborate implementation could even contain
different types per some condition at the runtime or anything at all.
The code:

TYPE_CHECKING = False
if TYPE_CHECKING:
    from .process import ProcessPoolExecutor
    from .thread import ThreadPoolExecutor

works for type checking in PyCharm and is fast.

This is how stdlib can be an example to how side libraries can be
implemented. If we can agree that this is the only clear, performant
and sufficient code - then perhaps modifying mypy is a reasonable
price to pay.

Perhaps this particular case can be just patched locally by PyCharm
/JetBrains, but what is a general solution to this class of problems?

Best Regards,
--
Ilya Kamenshchikov


On Tue, Apr 23, 2019 at 7:05 PM Guido van Rossum <guido at python.org> wrote:

> In any case I think this should be filed (by the OP) as an issue against
> JetBrains' PyCharm issue tracker. Who knows they may be able to
> special-case this in a jiffy. I don't think we should add any clever hacks
> to the stdlib for this.
>
> On Tue, Apr 23, 2019 at 9:59 AM Nathaniel Smith <njs at pobox.com> wrote:
>
>> On Tue, Apr 23, 2019, 05:09 Andrew Svetlov <andrew.svetlov at gmail.com>
>> wrote:
>>
>>> I agree that `from typing import TYPE_CHECKING` is not desirable from
>>> the import time reduction perspective.
>>>
>>> From my understanding code completion *can* be based on type hinting
>>> to avoid actual code execution.
>>> That's why I've mentioned that typeshed already has the correct type
>>> information.
>>>
>>> if TYPE_CHECKING:
>>>     import ...
>>>
>>> requires mypy modification.
>>>
>>> if False:
>>>     import ...
>>>
>>> Works right now for stdlib (mypy ignores stdlib code but uses typeshed
>>> anyway) but looks a little cryptic.
>>> Requires a comprehensive comment at least.
>>>
>>
>> Last time I looked at this, I'm pretty sure `if False` broke at least one
>> popular static analysis tool (ie it was clever enough to ignore everything
>> inside `if False`) – I think either pylint or jedi?
>>
>> I'd suggest checking any clever hacks against at least: mypy,
>> pylint/astroid, jedi, pyflakes, and pycharm. They all have their own static
>> analysis engines, and each one has its own idiosyncratic quirks.
>>
>> We've struggled with this a *lot* in trio, and eventually ended up giving
>> up on all forms of dynamic export cleverness; we've even banned the use of
>> __all__ entirely. Static analysis has gotten good enough that users won't
>> accept it not working, but it hasn't gotten good enough to handle anything
>> but the simplest static exports in a reliable way:
>>     https://github.com/python-trio/trio/pull/316
>>     https://github.com/python-trio/trio/issues/542
>>
>> The stdlib has more leeway because when tools don't work on the stdlib
>> then they tend to eventually add workarounds. I'm just saying, think twice
>> before diving into clever hacks to workaround static analysis limits, and
>> if you're going to do it then be careful to be thorough. You're basically
>> relying on undocumented bugs, and it gets really messy really quickly.
>>
>> -n
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>
>
> --
> --Guido van Rossum (python.org/~guido)
> *Pronouns: he/him/his **(why is my pronoun here?)*
> <http://feministing.com/2015/02/03/how-using-they-as-a-singular-pronoun-can-change-the-world/>
>
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