`WarningsRecorder.pop()` returns the last match instead of the first when warning categories are unrelated

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@Aditya-XR arbeitet bereits daran.

Seit 24.9.2026.

  • #15098 von @Aditya-XR — offen
  • #15105 von @chen-maker999 — ohne Merge geschlossen
  • #15119 von @Tejas5405 — offen

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35/100
Issue-Typ
Bug
Klarheit
Klar beschrieben
Aktivitätsstatus
Aktiv
Tech-Stack
python
Bereich
testing-qa

Rechercherichtung

Start at the WarningsRecorder.pop implementation and read TestSubclassWarningPop plus test_recording, especially the existing category-selection loop. Add a regression case using unrelated warning categories and verify that pop returns the first matching warning; run the relevant warning-recorder tests.

Vom Indexierungsmodell aus dem Issue-Text verfasst.

Beschreibung

WarningsRecorder.pop() (and pytest.warns(...).pop() / recwarn.pop()) returns the last matching warning instead of the first one when the recorded warnings have categories that are unrelated to each other.

import warnings

def test_pop(recwarn):
    warnings.warn("first", UserWarning)
    warnings.warn("second", RuntimeWarning)
    warnings.warn("third", DeprecationWarning)
    assert str(recwarn.pop().message) == "first"

E       AssertionError: assert 'third' == 'first'

The docstring says pop returns "the first recorded warning which is an instance of cls, but not an instance of a child class of any other match". None of the three categories is a subclass of another, so the first one should come back. That was also the behaviour before 8.0.

The cause is the "best inexact match" loop added in #11160 (the fix for #10701):

if issubclass(w.category, cls) and (
    best_idx is None
    or not issubclass(w.category, self._list[best_idx].category)
):
    best_idx = i

not issubclass(new, best) is true both when new is more general than best and when the two are unrelated siblings. So every sibling replaces the current best, and the loop ends up on the last one.

The existing tests in TestSubclassWarningPop only use a single parent/child chain, so they don't catch this. test_recording pops a UserWarning and a DeprecationWarning, but both have the message "hello", so it passes whichever one comes back.

Reproduced on main (pytest 9.2.0.dev345+g872117358), Python 3.13.5, Windows 11. The loop was introduced by #11160, so the bug is present since 8.0.0; in 7.4.x pop() returned the first match. I have a fix with regression tests ready and will open a PR.

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Erste Schritte

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  3. Forken Sie das Repository und arbeiten Sie in einem Branch.
  4. Öffnen Sie einen Pull Request, der die Issue-Nummer nennt.

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