Windows 10 Pro 64
Python 3.8.3 64
wxPython 4.1.0

It appears that there are synthetic classes in the mro, which don't appear in the type's namespace, raising KeyError when encountered.  From reading the function's doc and source, it looks like it should handle this internally and return a valid dict (possibly empty), and not raise KeyError.

>>> import typing, wx
>>> typing.get_type_hints(wx.Window)'
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "C:\Program Files\Python38\lib\typing.py", line 1223, in get_type_hints
    base_globals = sys.modules[base.__module__].__dict__

>>> wx.Window.mro()
[<class 'wx._core.Window'>, <class 'wx._core.WindowBase'>, <class 'wx._core.EvtHandler'>, <class 'wx._core.Object'>, <class 'wx._core.Trackable'>, <class 'sip.wrapper'>, <class 'sip.simplewrapper'>, <class 'object'>]

KeyError: 'sip'

Hm, the fix would seem simple enough. Can you submit a PR? It would be nice if it had a test as well.

I guess more libraries will experience this with `from __future__ import annotations` becoming default in Python 3.10 and they switch to get_type_hints.

https://github.com/sphinx-doc/sphinx/issues/8084
https://github.com/facebook/TestSlide/issues/296

New changeset a9cf69df2e031d6157f01289f66ca9cf723ceb5c by Karthikeyan Singaravelan in branch 'master':
bpo-41515: Fix KeyError raised in get_type_hints (GH-25352)
https://github.com/python/cpython/commit/a9cf69df2e031d6157f01289f66ca9cf723ceb5c

This change introduced a regression:
https://buildbot.python.org/all/#/builders/96/builds/1012

$ ./python -m test test___all__
0:00:00 load avg: 0.28 Run tests sequentially
0:00:00 load avg: 0.28 [1/1] test___all__
test test___all__ failed -- Traceback (most recent call last):
  File "/home/vstinner/python/master/Lib/test/test___all__.py", line 104, in test_all
    self.check_all(modname)
  File "/home/vstinner/python/master/Lib/test/test___all__.py", line 25, in check_all
    exec("import %s" % modname, names)
  File "/home/vstinner/python/master/Lib/contextlib.py", line 140, in __exit__
    next(self.gen)
  File "/home/vstinner/python/master/Lib/test/support/warnings_helper.py", line 177, in _filterwarnings
    raise AssertionError("unhandled warning %s" % reraise[0])
AssertionError: unhandled warning {message : SyntaxWarning('assertion is always true, perhaps remove parentheses?'), category : 'SyntaxWarning', filename : '/home/vstinner/python/master/Lib/test/test_typing.py', lineno : 2275, line : None}

test___all__ failed

== Tests result: FAILURE ==

1 test failed:
    test___all__

Total duration: 2.7 sec
Tests result: FAILURE


It comes from the following line of test_bad_module() in Lib/test/test_typing:

    assert(get_type_hints(BadModule), {})

assert should be used as "assert test" or "assert test, expr". assert (expr, expr) tests if the tuple (2 items) is true, and it's always true.

Thanks -- odd this didn't fail in CI. We'll get it fixed.

> Thanks -- odd this didn't fail in CI.

The CI runs tests with "make buildbottest" which uses the -w option:

  -w, --verbose2        re-run failed tests in verbose mode

When test___all__ is re-run in verbose mode, it doesn't fail:

"== Tests result: FAILURE then SUCCESS =="

Thanks Victor. I have created https://github.com/python/cpython/pull/25379 that uses self.assertEqual instead of assert that produces syntax warning.

I see that all PRs are merged, and the CI issue is fixed as well. I close the issue.

commit eb77133564d74eb09ed63872a69b9827d4841b49
Author: Karthikeyan Singaravelan <tir.karthi@gmail.com>
Date:   Tue Apr 13 19:24:23 2021 +0530

    bpo41515: Fix assert in test which throws SyntaxWarning. (#25379)