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bpo-16845: Validate the category of warnings.simplefilter sooner #31983

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bpo-16845: Validate the category of warnings.simplefilter sooner
DanielNoord Mar 18, 2022
225990a
Potential fix?
DanielNoord Mar 18, 2022
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23 changes: 23 additions & 0 deletions Lib/test/test_warnings/__init__.py
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Original file line number Diff line number Diff line change
Expand Up @@ -545,6 +545,29 @@ class NonWarningSubclass:
self.module.warn('good warning category', MyWarningClass)
self.assertIsInstance(cm.warning, Warning)

def test_simplefilter_invalid_category(self):
class MyWarningClass(Warning):
pass

class NonWarningSubclass:
pass

msg_regex = 'category must be a Warning subclass, not (.*)'

with self.assertRaisesRegex(TypeError, msg_regex):
self.module.simplefilter('always', '')

with self.assertRaisesRegex(TypeError, msg_regex):
self.module.simplefilter('always', NonWarningSubclass)

with self.assertRaisesRegex(TypeError, msg_regex):
self.module.simplefilter('always', MyWarningClass())

with original_warnings.catch_warnings(module=self.module, record=True) as w:
self.module.simplefilter('always', MyWarningClass)
self.assertEqual(len(w), 0)


class CWarnTests(WarnTests, unittest.TestCase):
module = c_warnings

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6 changes: 5 additions & 1 deletion Lib/unittest/case.py
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Expand Up @@ -274,7 +274,11 @@ def __enter__(self):
v.__warningregistry__ = {}
self.warnings_manager = warnings.catch_warnings(record=True)
self.warnings = self.warnings_manager.__enter__()
warnings.simplefilter("always", self.expected)
if isinstance(self.expected, tuple):
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@DanielNoord DanielNoord Mar 18, 2022

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This should probably be done in a separate PR, but issubclass does not support a tuple. However, the type of the category parameter of warnings.simplefilter doesn't really indicate that it should support a tuple anyway.
I could also change it so that the issubclass checks for tuples before doing the check, but I'm not sure if that is actually correct.

Let me know!

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@serhiy-storchaka serhiy-storchaka Dec 1, 2023

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I think that there may be a third-party code which uses simplefilter() with a tuple. Instead of changing unittest, it is better to make the argument check in simplefilter() more lenient.

It would be nice to make also filterwarnings() accepting a tuple.

for expected in self.expected:
warnings.simplefilter("always", expected)
else:
warnings.simplefilter("always", self.expected)
return self

def __exit__(self, exc_type, exc_value, tb):
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3 changes: 3 additions & 0 deletions Lib/warnings.py
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Expand Up @@ -176,6 +176,9 @@ def simplefilter(action, category=Warning, lineno=0, append=False):
"once"), "invalid action: %r" % (action,)
assert isinstance(lineno, int) and lineno >= 0, \
"lineno must be an int >= 0"
if not (isinstance(category, type) and issubclass(category, Warning)):
raise TypeError('category must be a Warning subclass, '
'not {!r}'.format(category))
_add_filter(action, None, category, None, lineno, append=append)

def _add_filter(*item, append):
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1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Library/2022-03-18-20-48-24.bpo-16845.gWkP5A.rst
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@@ -0,0 +1 @@
Validate the category of warnings.simplefilter sooner