gh-105936: Properly update closure cells for __setattr__ and __delattr__ in frozen dataclasses with slots#144021
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gpshead merged 14 commits intopython:mainfrom Apr 12, 2026
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Thanks! For the test you can do something like that in the original fix, https://github.com/python/cpython/pull/137047/files#diff-212e368b34eb9b134f87e765787d6d26b747235a358e13da8922f83861c0d676 . |
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__setattr__ and __detattr__ in frozen dataclasses with slots__setattr__ and __detattr__ in frozen dataclasses with slots
Misc/NEWS.d/next/Library/2026-01-19-21-23-18.gh-issue-105936.dGrzjM.rst
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JelleZijlstra
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While this PR is not merged, should AKCS be updated? |
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If I remember correctly the latest policy on Misc/ACKS is that people can add themselves if they want but it's not required. The file is a pain to keep fully correct and sort of redundant with |
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gpshead
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__setattr__ and __detattr__ in frozen dataclasses with slots__setattr__ and __delattr__ in frozen dataclasses with slots
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needs backport to 3.13
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Thanks @Prometheus3375 for the PR, and @gpshead for merging it 🌮🎉.. I'm working now to backport this PR to: 3.13, 3.14. |
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…`__delattr__` in frozen dataclasses with slots (pythonGH-144021) (cherry picked from commit 8a398bf) Co-authored-by: Sviataslau <35541026+Prometheus3375@users.noreply.github.com>
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Sorry, @Prometheus3375 and @gpshead, I could not cleanly backport this to |
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GH-148469 is a backport of this pull request to the 3.14 branch. |
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…`__delattr__` in frozen dataclasses with slots (pythonGH-144021) (cherry picked from commit 8a398bf) Co-authored-by: Sviataslau <35541026+Prometheus3375@users.noreply.github.com>
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… `__delattr__` in frozen dataclasses with slots (GH-144021) (#148469) gh-105936: Properly update closure cells for `__setattr__` and `__delattr__` in frozen dataclasses with slots (GH-144021) (cherry picked from commit 8a398bf) Co-authored-by: Prometheus3375 <prometheus3375@gmail.com> Co-authored-by: Sviataslau <35541026+Prometheus3375@users.noreply.github.com>
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…_` and `__delattr__` in frozen dataclasses with slots (pythonGH-144021) pythongh-105936: Properly update closure cells for `__setattr__` and `__delattr__` in frozen dataclasses with slots (pythonGH-144021) (cherry picked from commit 8a398bf) The cherry-pick required additional changes beyond the original commit because 3.13 lacks the `__class__` closure cell fixup machinery that was added in 3.14 by pythonGH-124455 (pythongh-90562). Specifically: - Backported `_update_func_cell_for__class__()` helper function and the closure fixup loop in `_add_slots()` from pythonGH-124455. Without these, renaming the closure variable from `cls` to `__class__` has no effect because nothing updates the cell when the class is recreated with slots. - Changed `_add_slots()` to use `newcls` instead of reusing `cls` for the recreated class, so both old and new class references are available for the fixup loop. - Replaced `assertNotHasAttr` with `assertFalse(hasattr(...))` in tests (assertNotHasAttr was added in 3.14). - Dropped `test_original_class_is_gced` additions (that test does not exist on 3.13; it was added by pythonGH-137047 for pythongh-135228 which was not backported to 3.13). Co-authored-by: Prometheus3375 <prometheus3375@gmail.com> Co-authored-by: Sviataslau <35541026+Prometheus3375@users.noreply.github.com> Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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GH-148476 is a backport of this pull request to the 3.13 branch. |
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Specifying
frozen=Truefor a dataclass adds methods__setattr__and__detattr__to it. These methods reference the class via closure. Ifslots=Trueis also present, then the class is recreated with slots with all methods being copied. Notably, every method referencing the old class via closure in variable__class__is properly updated, but__setattr__and__detattr__reference the old class viacls; hence, they are still referencing the old class instead of the new one. This PR fixes this issue.__setattr__and__delattr__does not work. #105936Additional details:
The issue is present in Python as early as in 3.10. This PR must be backported to 3.14 and possibly 3.13.
Originally this PR was referencing gh-135228, but soon I realized that the issue is not connected to regression in 3.14. There is an older PR #105937 that fixes the issue, but it is heavily outdated.