Karthikeyan Singaravelan <[email protected]> added the comment:
When mock.patch is creates a patch object and patch.start calls __enter__ that
sets is_local. On stop __exit__ is called where a check is done is to make sure
is_local attribute is present and then cleanup is done along with deleting
calling del self.is_local so calling stop second time causes the attribute
check to fail. There is no specific reason I could find with git history.
It seems that calling patch.stop without patch.start makes cleanup to happen on
unpatched objects and raises errors which I hope is avoided by always setting
is_local on start and removing it on stop like a flag. That being said I am not
sure why a early return couldn't be made when is_local is absent instead of
proceeding with cleanup logic or raising a runtime error. I see no tests
failing on early return except a test where RuntimeError is intentionally
tested by calling stop on unstarted patch. I have added mock module devs for
some context.
A sample script would be as below :
from unittest import mock
class Foo:
bar = None
patch = mock.patch.object(Foo, 'bar', 'x')
patch.start()
patch.stop()
patch.stop()
----------
nosy: +xtreak
type: -> behavior
versions: +Python 3.8
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<https://bugs.python.org/issue36366>
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