Fix monkeypatch undo when deleting missing attrs/items with raising=False#14271
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kartikdp wants to merge 1 commit intopytest-dev:mainfrom
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Fix monkeypatch undo when deleting missing attrs/items with raising=False#14271kartikdp wants to merge 1 commit intopytest-dev:mainfrom
kartikdp wants to merge 1 commit intopytest-dev:mainfrom
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nicoddemus
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Mar 13, 2026
| assert A.x == 1 | ||
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| def test_delattr_non_existing_with_raising_false() -> None: |
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This test already passes on main, so it is not reflecting/reproducing the issue.
Did you intend to use setattr directly to set x (instead of monkeypatch.setattr).
| assert d == {"hello": "world", "x": 1} | ||
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| def test_delitem_non_existing_with_raising_false() -> None: |
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Same comment as the other test.
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| Fixed ``MonkeyPatch.delattr(..., raising=False)`` and ``MonkeyPatch.delitem(..., raising=False)`` so ``undo()`` restores the original missing state. | |||
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Not sure if this is a bug-fix, seems like an improvement: now delattr will always delete the attribute at the end of the test.
This is a behavior change which I don't think can cause problems later, as it depends on the user explicitly calling monkeydelattr.delattr(..., raising=False).
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@The-Compiler you commented on the issue; are you OK with this?
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Summary
Fixes a state-restoration bug in
MonkeyPatchwhen deleting a missing attribute/item withraising=False.Previously:
delattr(..., raising=False)anddelitem(..., raising=False)did not record the missing state.undo()would not reliably restore the original missing state.This change records
NOTSETfor those delete calls, and makesundo()tolerant when the target attribute is already absent.Closes #14094.
Why this matters
Tests that use non-raising deletes expect monkeypatch teardown to fully restore pre-test state. Without this fix, state could leak after tests.
How tested
uv run -m pytest testing/test_monkeypatch.py -k "delattr_non_existing_with_raising_false or delitem_non_existing_with_raising_false or test_delattr or test_delitem"uv run -m pytest testing/test_monkeypatch.pyuv run --with pre-commit pre-commit run --files src/_pytest/monkeypatch.py testing/test_monkeypatch.py changelog/14094.bugfix.rst