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fix: monkeypatch.setattr undo on objects with custom __setattr__ (#15099) - #15130
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When the target has a custom __setattr__ that doesn't write into the instance __dict__, the old value was recorded as NOTSET, causing undo() to call delattr() instead of restoring the original value. Only use the __dict__ lookup when name is actually present in the instance __dict__, or when the type uses object.__setattr__. Otherwise fall back to the value from getattr(). Fixes pytest-dev#15099
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…est-dev#15099) Bind the patched read to a local so mypy doesn't narrow the attribute to Literal[False] and mark undo() unreachable.
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Closing as a duplicate of #15118 (opened by @Tejas5405 on Oct 1, three days before this one). I should have caught the earlier comment pointing this out on Oct 4 and stood down then. Leaving #15118 to the maintainers. |
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Problem
Since #14969 (0c601d5, not released yet),
monkeypatch.setattrdoesn't restore attributes on objects that store them somewhere other than__dict__through a custom__setattr__/__getattr__. Undo raisesAttributeError, and the patched value leaks into later tests.Changes
__dict__lookup whennameis actually present in the instance__dict__, or when the type usesobject.__setattr__. Otherwise fall back to the value fromgetattr().__setattr__objectsVerification