Code that uses import arcade doesn't type check properly with mypy

[SirGnip]

Bug Report

When using mypy to type check projects that depend on arcade, mypy is unable to handle code imported from arcade.

Actual behavior:

When using mypy to type check code that imports arcade with the style in the documentation & example code, mypy reports errors like "Module has no attribute ..."

Expected behavior:

It is expected that code that relies on import arcade should type hint cleanly with mypy.

Steps to reproduce/example code:

The code snippet below uses the suggested import arcade style of importing the arcade package. It runs as expected. However, when you type check it with mypy, errors are returned:

# simple1.py
import arcade
s = arcade.Sprite()

$ mypy --strict simple1.py
simple1.py:2: error: Module has no attribute "Sprite"
Found 1 error in 1 file (checked 1 source file)

The Sprite is obviously there because the code runs as expected. mypy can't find it.

Same behavior with a slightly different import method:

# simple2.py
from arcade import Sprite
s = Sprite()

$ mypy --strict simple2.py
simple2.py:1: error: Module 'arcade' has no attribute 'Sprite'
Found 1 error in 1 file (checked 1 source file)

Interestingly, a more explicit method of importing arcade both runs and type checks properly. However, this style of importing isn't in the documentation or arcade example code:

# simple3.py
from arcade.sprite import Sprite
s = Sprite()

$ mypy --strict simple3.py
Success: no issues found in 1 source file

I'm guessing this is happening because of the from arcade.sprite import * style imports arcade does in its __init__.py flie to get everything into the arcade namespace. Maybe mypy can't follow the imports and fails? In general, I believe the * style of importing is discouraged.

The fix might be to change the from arcade.sprite import * style imports in __init__.py to from arcade.sprite import Sprite, AnimationKeyframe, AnimatedTimeBasedSprite, AnimatedWalkingSprite, get_distance_between_sprites. Obviously more verbose and a bit more to maintain. But, it is explicit.

[pvcraven]

I like the idea of changing the import * statements. Might also help with issues I'm having on building docs. I'll play around with it.

[pvcraven]

Working on this now. Wrote a program to auto-pull out a lot of this. There's a lot of dependency stuff to slog through, and other bugs that popped up.

[SirGnip]

I fetched the current master and ran the mypy tests documented in #533 . They came back clean. So, the __init__.py restructuring seems to have made mypy happy...

[pvcraven]

Yes! Great news.

[SirGnip]

Good news / bad news. :) As I said, type checking is happy, but I just discovered runtime isn't. Complaining about No module named 'window_commands'. See the new issue I just created #546.

[pvcraven]

Yeah, I haven't figured that one out yet.

[pvcraven]

Ok, looks like I need to prepend a period.

from .window_commands import whatever

[pvcraven]

Mypy now running clean in the codebase.

[SirGnip]

I pulled the most recent master down and mypy runs cleanly for me as well.

[pvcraven]

Closed with release of 2.2.7.