Issues when str is defined as a class variable

[max-sixty]

Environment data

• Language Server version: 2020.6.1
• OS and version: MacOS
• Python version (& distribution if applicable, e.g. Anaconda): Python3.7

@jakebailey asked me to open a new issue here. As discussed in #15 (comment), and microsoft/python-language-server#1732, this causes > 50 errors in https://github.com/pydata/xarray/blob/v0.15.1/xarray/core/dataarray.py.

The reproduction is there, but copying the essentials here:

It's on this line: https://github.com/pydata/xarray/blob/v0.15.1/xarray/core/dataarray.py#L242
And I suspect caused by this definition of str: https://github.com/pydata/xarray/blob/v0.15.1/xarray/core/dataarray.py#L3435

Please let me know if it would be helpful to produce logs.

Thank you!

[jakebailey]

@erictraut

Maybe I'm misunderstanding the scoping rule, but given str is being declared as a class variable, is it not only accessible by say ClassName.str?

[jakebailey]

I would also suggest trying to do the method described in microsoft/python-language-server#1732 (comment), though, as it would certainly prevent that aliasing.

[erictraut]

@jakebailey, if you're within the class, you don't need to use the class name to refer to the class variable. For example, this runs fine and prints "3".

class Foo:
    str = 3
    str2 = str
    print(str2)

[jakebailey]

Ah, that explains a lot. Unfortunate.

[max-sixty]

This is fixed with the suggestion in (2): pydata/xarray@5c09276

It's not super convenient, as a new contributor is going to slip up at some point given mypy currently allows it, so let me reflect on which path we take. And I recognize it's on us for picking str as a class variable (I think we were following pandas convention, which was probably from a decade ago...)

Thanks for the engagement and guidance

[jakebailey]

Out of curiosity, why update the docstrings to contain the "fake" type? Or are you somehow generating those docs from the type annotations?

[max-sixty]

Sorry, that was a regex replace, I won't keep those