[Python-Dev] Concurrent.futures: no type discovery for PyCharm (original) (raw)

Nathaniel Smith njs at pobox.com
Tue Apr 23 12:54:20 EDT 2019

On Tue, Apr 23, 2019, 05:09 Andrew Svetlov <andrew.svetlov at gmail.com> wrote:

I agree that from typing import TYPECHECKING 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 TYPECHECKING: 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.

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