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gh-148947: dataclasses: fix error on empty __class__ cell #148948

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JelleZijlstra merged 2 commits intopython:mainfrom
JelleZijlstra:weirdclass
Apr 25, 2026
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gh-148947: dataclasses: fix error on empty __class__ cell #148948
JelleZijlstra merged 2 commits intopython:mainfrom
JelleZijlstra:weirdclass

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@JelleZijlstra JelleZijlstra commented Apr 24, 2026

Also add a test demonstrating the need for the existing "is oldcls" check.

Also add a test demonstrating the need for the existing "is oldcls" check.
@JelleZijlstra JelleZijlstra added the needs backport to 3.14 bugs and security fixes label Apr 24, 2026
@johnslavik johnslavik changed the title gh-148947: dataclasses: fix crash on empty __class__ cell gh-148947: dataclasses: fix error on empty __class__ cell Apr 24, 2026
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Nice catch! 🚀

Comment thread Lib/test/test_dataclasses/__init__.py Outdated
@johnslavik johnslavik changed the title gh-148947: dataclasses: fix error on empty __class__ cell gh-148947: dataclasses: fix crash on empty __class__ cell Apr 24, 2026
@johnslavik johnslavik changed the title gh-148947: dataclasses: fix crash on empty __class__ cell gh-148947: dataclasses: fix error on empty __class__ cell Apr 24, 2026
Co-authored-by: Bartosz Sławecki <bartosz@ilikepython.com>
@JelleZijlstra JelleZijlstra merged commit 6d7bbee into python:main Apr 25, 2026
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Thanks @JelleZijlstra for the PR 🌮🎉.. I'm working now to backport this PR to: 3.14.
🐍🍒⛏🤖

@JelleZijlstra JelleZijlstra deleted the weirdclass branch April 25, 2026 15:31
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bedevere-app Bot commented Apr 25, 2026

GH-148995 is a backport of this pull request to the 3.14 branch.

@bedevere-app bedevere-app Bot removed the needs backport to 3.14 bugs and security fixes label Apr 25, 2026
ljfp pushed a commit to ljfp/cpython that referenced this pull request Apr 25, 2026
…on#148948)

Also add a test demonstrating the need for the existing "is oldcls" check.

Co-authored-by: Bartosz Sławecki <bartosz@ilikepython.com>
JelleZijlstra added a commit that referenced this pull request Apr 25, 2026
…148948) (#148995)

gh-148947: dataclasses: fix error on empty __class__ cell  (GH-148948)

Also add a test demonstrating the need for the existing "is oldcls" check.
(cherry picked from commit 6d7bbee)

Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>
Co-authored-by: Bartosz Sławecki <bartosz@ilikepython.com>
gpshead added a commit to gpshead/cpython that referenced this pull request Apr 25, 2026
pythonGH-148948)

pythongh-148947: dataclasses: fix error on empty __class__ cell  (pythonGH-148948)

Also add a test demonstrating the need for the existing "is oldcls" check.
(cherry picked from commit 6d7bbee)

Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>
Co-authored-by: Bartosz Sławecki <bartosz@ilikepython.com>
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
gpshead added a commit to gpshead/cpython that referenced this pull request Apr 25, 2026
pythonGH-148948)

pythongh-148947: dataclasses: fix error on empty __class__ cell  (pythonGH-148948)

Also add a test demonstrating the need for the existing "is oldcls" check.
(cherry picked from commit 6d7bbee)

Consolidates the news entries given pythonGH-148947 bug was never present in the 3.13
branch

Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>
Co-authored-by: Bartosz Sławecki <bartosz@ilikepython.com>
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
gpshead added a commit that referenced this pull request Apr 26, 2026
…_delattr__ in frozen dataclasses with slots (GH-144021) (GH-148476)

gh-105936: Properly update closure cells for `__setattr__` and `__delattr__` in frozen dataclasses with slots (GH-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 GH-124455 (gh-90562). Specifically:

- Backported `_update_func_cell_for__class__()` helper function and the
  closure fixup loop in `_add_slots()` from GH-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 GH-137047 for gh-135228 which was not
  backported to 3.13).

gh-148947: dataclasses: fix error on empty __class__ cell  (GH-148948)

Also add a test demonstrating the need for the existing "is oldcls" check.
(cherry picked from commit 6d7bbee)

---------

Co-authored-by: Prometheus3375 <prometheus3375@gmail.com>
Co-authored-by: Sviataslau <35541026+Prometheus3375@users.noreply.github.com>
Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>
Co-authored-by: Bartosz Sławecki <bartosz@ilikepython.com>
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2 participants