Accept math constants in defaults

[XuehaiPan]

Allow math.inf, math.e, math.pi, math.tau, and their negatives in defaults.

Reject:

• float('inf') / float('-inf'): function calls
• math.nan: not constant math.nan == math.nan -> False

Resolves #354

[AlexWaygood]

Thanks!

I don't think it needs to be nearly this complicated, though. If you just add these constants to the _ALLOWED_ATTRIBUTES_IN_DEFAULTS frozenset, I don't think you'll need to make any other changes to pyi.py

[XuehaiPan]

I don't think it needs to be nearly this complicated, though.

I think -math.inf should be allowed here.

$ echo 'import math; x = -math.inf' | python3 -m ast
Module(
   body=[
      Import(
         names=[
            alias(name='math')]),
      Assign(
         targets=[
            Name(id='x', ctx=Store())],
         value=UnaryOp(
            op=USub(),
            operand=Attribute(
               value=Name(id='math', ctx=Load()),
               attr='inf',
               ctx=Load())))],
   type_ignores=[])

The AST for -math.inf is UnaryOp.

[AlexWaygood]

Ah, I see. That requires a slightly more invasive change to the code than I was expecting, but I suppose it's reasonable.

[AlexWaygood]

Could you add a CHANGELOG entry? This file here: https://github.com/PyCQA/flake8-pyi/blob/main/CHANGELOG.md

[AlexWaygood]

A few changelog nitpicks :)

[AlexWaygood]

This set is small enough that we could probably actually just inline it in the _is_valid_math_constant function. But on the other hand, I guess having it as a global constant like this maybe makes the code more extensible, if we want to add this to this set in the future. No strong opinion either way.

[XuehaiPan]

Since the function will be called multiple times, caching the frozenset as a global variable will somehow gain some speed. And also, it would be extensible.

[AlexWaygood]

LGTM, but I'll wait a little bit before merging in case any other maintainers have objections :)

[github-actions]

This change has no effect on typeshed. 🤖🎉

[AlexWaygood]

Thanks @XuehaiPan!