[New-bugs-announce] [issue45836] unittest.TestCase.assertWarns raises RuntimeEror if sys.modules changes size (Python 3.9)
Patrick Bourke
report at bugs.python.org
Wed Nov 17 19:47:42 EST 2021
New submission from Patrick Bourke <pbourke at microsoft.com>:
Hi all,
Forgive me if this is not the correct way to report this, but we have run into the issue from #29620 ( https://bugs.python.org/issue29620 ) on Python 3.9.
The fix appears to be present in the tip of 3.8:
https://github.com/python/cpython/blob/c37a0d9c0ae4aa0d9135fac9a58afc7b34ff71d6/Lib/unittest/case.py#L254
and 3.10:
https://github.com/python/cpython/blob/0ef308a2890571c850c624fb99ac00f8951363c6/Lib/unittest/case.py#L255
but missing from 3.9:
https://github.com/python/cpython/blob/0ef308a2890571c850c624fb99ac00f8951363c6/Lib/unittest/case.py#L255
Here is our test case:
import unittest
import graspologic
class MyTestCase(unittest.TestCase):
def test_something(self):
with self.assertWarns(UserWarning):
pass
if __name__ == '__main__':
unittest.main()
fails with:
======================================================================
ERROR: test_something (__main__.MyTestCase)
----------------------------------------------------------------------
Traceback (most recent call last):
File "C:\Users\pbourke\AppData\Roaming\JetBrains\PyCharm2021.2\scratches\test.py", line 7, in test_something
with self.assertWarns(UserWarning):
File "C:\Users\pbourke\.pyenv\pyenv-win\versions\3.9.7\lib\unittest\case.py", line 255, in __enter__
for v in sys.modules.values():
RuntimeError: dictionary changed size during iteration
The module triggering the error appears to be IPython.utils.io, which is included somewhere in our dependencies.
My CPython is:
Python 3.9.7 (tags/v3.9.7:1016ef3, Aug 30 2021, 20:19:38) [MSC v.1929 64 bit (AMD64)]
----------
components: Library (Lib)
messages: 406516
nosy: pbourke
priority: normal
severity: normal
status: open
title: unittest.TestCase.assertWarns raises RuntimeEror if sys.modules changes size (Python 3.9)
type: behavior
versions: Python 3.9
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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue45836>
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