How can I make this # type: ignore platform specific?

[evandrocoan]

The project I use, runs both on Windows and Linux. The code is all platform specific, but mypy keeps ignoring it:

File: anki/pylib/anki/utils.py
286: def call(argv: List[str], wait: bool = True, **kwargs) -> int:
287:     "Execute a command. If WAIT, return exit code."
288:     # ensure we don't open a separate window for forking process on windows
289:     if isWin:
290:         si = subprocess.STARTUPINFO()
291:         try:
292:             si.dwFlags |= subprocess.STARTF_USESHOWWINDOW

1. If I add # type: ignore to lines 290 and 292 then, mypy works on Linux, but it fails on Windows with error: unused 'type: ignore' comment
2. If I remove the # type: ignore from the lines 290 and 292 then, mypy works on Windows, but it fails on Linux with error: Module has no attribute "STARTUPINFO" [attr-defined].

The STARTUPINFO is not defined for Linux Implementations, but is is for Windows implementation. That is why both of them are both protected by a if isWin or if _mswindows on this project and on the subprocess module implementation:

File: F:/Python/lib/subprocess.py
164: if _mswindows:
165:     class STARTUPINFO:

How can I make this # type: ignore platform specific?

(pyenv) F:\anki>mypy --version
mypy 0.761

[JelleZijlstra]

If you use a mypy-recognized platform check like if sys.platform == 'win32', mypy should behave as expected.

[evandrocoan]

The isWin Anki uses on the if is this:

File: anki/pylib/anki/utils.py
323: isWin = sys.platform.startswith("win32")

The only way to mypy to work is replacing the if isWin by if sys.platform == 'win32'? This should be improved.

[JukkaL]

Mypy supports what specified in PEP 484 (https://www.python.org/dev/peps/pep-0484/#version-and-platform-checking). We could perhaps extend this to cover more cases, but it's hard to decide where we should draw the line, since the platform checks could be arbitrarily creative.

[ErikBjare]

@JukkaL I'm having problems with a simple case like:

if platform.system() == "Windows":
    something_platform_specific()  # type: ignore

There are some valid cases where you might want to do this, especially for Windows where sys.platform can be one of ["win32", "cygwin"].

Edit: I tried with this and it worked:

if platform.sys == "win32" or platform.sys == "cygwin":
    something_platform_specific()

[JelleZijlstra]

There is an open PR #8461 to add support for platform.system(), but it looks like it has stalled.

[hauntsaninja]

Closing this as a dupe of other issues, basically this entire comment #9242 (comment) applies to this issue