Version 1.5.0 breaks argpare.parse_args(namespace)

[kovidgoyal]

Here is a test case:

import argparse

class Options(argparse.Namespace):
    something: bool = True

p = argparse.ArgumentParser()
a: Options = p.parse_args(namespace=Options())

Running mypy version 1.5.0 on it gives the spurious error

10: error: Incompatible types in assignment (expression has type "Namespace", variable has type "Options")  [assignment]
    a: Options = p.parse_args(namespace=Options())
                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Found 1 error in 1 file (checked 1 source file)

Running mypy version 1.3.0 on it passes.

[cdce8p]

I bisected the issue to 59a6c5e. Seems like an issue with the argparse typing stubs.
Looks like it's already fixed in typeshed, however the sync didn't make it in time for this release. Probably in 1.6.0 then.

• Fix namespace argument regression in argparse.parse_args typeshed#10387
• Sync typeshed #15792

CC @AlexWaygood

[AlexWaygood]

Yeah, the issue was cause by python/typeshed#10307, which made it into mypy v1.5. It's already been fixed on typeshed's main branch by python/typeshed#10387, but the fix unfortunately didn't make it into mypy v1.5.

Since python/typeshed#10387 was a fairly small PR, it could possibly be cherry-picked into the next mypy patch release. However, I know @svalentin has already created the mypy 1.5.1 tag, so I'm not sure if it's possible to get a fix into mypy 1.5.1 :/

(We also can't create any new mypy releases at all until pypi/support#3094 is resolved)

[alicederyn]

This appears to be fixed in mypy 1.6.0.