gh-145876: preserve AttributeError in dict unpacking - #145878
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Pull request overview
This PR adjusts dict-unpacking ({**obj} / DICT_UPDATE) error handling so that AttributeError raised from within a mapping’s keys() / __getitem__ is propagated, instead of being incorrectly rewritten as TypeError: '... object is not a mapping'.
Changes:
- Update DICT_UPDATE to only convert AttributeError into “not a mapping” when update_o truly lacks a keys attribute; otherwise restore and propagate the original exception.
- Regenerate the tier-1 interpreter cases to include the updated error-handling logic.
- Add doctest coverage ensuring AttributeError from keys() / __getitem__ is preserved during dict unpacking.
Reviewed changes
Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.
| File | Description |
|---|---|
| Python/generated_cases.c.h | Regenerated tier-1 interpreter DICT_UPDATE case to preserve AttributeError from mapping internals. |
| Python/bytecodes.c | Updates the DICT_UPDATE bytecode definition’s error translation logic. |
| Lib/test/test_unpack_ex.py | Adds doctests to ensure {**obj} propagates AttributeError raised by keys() / __getitem__. |
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| PyObject *exc = PyErr_GetRaisedException(); | ||
| PyObject *keys = NULL; | ||
| int has_keys = PyObject_GetOptionalAttr(update_o, &_Py_ID(keys), &keys); | ||
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| if (has_keys < 0) { |
Copilot
AI
Mar 12, 2026
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DICT_UPDATE now preserves the original AttributeError only when update_o has a keys attribute, but the tier-2 interpreter (Python/executor_cases.c.h) is generated from bytecodes.c and currently still contains the old unconditional conversion of AttributeError into TypeError. This will make behavior differ between tier-1 and tier-2 execution (and can break the new tests when tier-2 is enabled). Please regenerate/update the tier-2 cases so DICT_UPDATE matches this new logic everywhere.
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Summary\n- preserve AttributeError raised from mapping methods during dict unpacking\n- keep TypeError for objects that are not mappings\n- add a regression test in test_unpack_ex\n\n## Testing\n- PCbuild\build.bat -p x64 -c Release\n- PCbuild\amd64\python.exe -m test -v test_unpack_ex\n\nCloses #145876