fix: use subclass check for AttributeError in getattr_opt on Python < 3.13#5985
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davidhewitt merged 4 commits intoPyO3:mainfrom Apr 24, 2026
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… 3.13 The `#[cfg(not(Py_3_13))]` branch of `getattr_opt` used `.is()` (type identity) to check for `AttributeError`, which missed subclasses. This replaces it with `.is_subclass_of::<PyAttributeError>()` to match the behavior of `PyObject_GetOptionalAttr` on Python 3.13+.
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Pull request overview
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Fixes getattr_opt behavior on Python < 3.13 to treat AttributeError subclasses as “attribute not found”, aligning with Python 3.13+ semantics, and adds a regression test.
Changes:
- Use subclass checking instead of type identity when determining whether to swallow an
AttributeErroringetattr_opt(Python < 3.13 path). - Add a unit test that raises an
AttributeErrorsubclass from a property and assertsgetattr_optreturnsNone. - Add a newsfragment documenting the fix.
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.
| File | Description |
|---|---|
| src/types/any.rs | Updates error-type checking in getattr_opt and adds a regression test for AttributeError subclasses. |
| newsfragments/5985.fixed.md | Documents the behavior fix for Python < 3.13. |
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Switch from `err.get_type().is_subclass_of::<PyAttributeError>()?` to `err.is_instance_of::<PyAttributeError>()` which is infallible and avoids masking the original error if the subclass check itself fails. This also matches the pattern used by `hasattr` in the same file.
davidhewitt
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Apr 18, 2026
…ions Add a compatibility shim for PyObject_GetOptionalAttr in pyo3-ffi/src/compat/py_3_13.rs that uses PyObject_GetAttr + PyErr_ExceptionMatches on Python < 3.13, matching the real C API behavior on 3.13+. Simplify getattr_opt to use the compat function unconditionally, removing the #[cfg] branching.
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Apr 23, 2026
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… 3.13 (PyO3#5985) * fix: use subclass check for AttributeError in getattr_opt on Python < 3.13 The `#[cfg(not(Py_3_13))]` branch of `getattr_opt` used `.is()` (type identity) to check for `AttributeError`, which missed subclasses. This replaces it with `.is_subclass_of::<PyAttributeError>()` to match the behavior of `PyObject_GetOptionalAttr` on Python 3.13+. * chore: rename newsfragment to PR PyO3#5985 * fix: use infallible is_instance_of instead of fallible is_subclass_of Switch from `err.get_type().is_subclass_of::<PyAttributeError>()?` to `err.is_instance_of::<PyAttributeError>()` which is infallible and avoids masking the original error if the subclass check itself fails. This also matches the pattern used by `hasattr` in the same file. * fix: add PyObject_GetOptionalAttr compat shim and use it for all versions Add a compatibility shim for PyObject_GetOptionalAttr in pyo3-ffi/src/compat/py_3_13.rs that uses PyObject_GetAttr + PyErr_ExceptionMatches on Python < 3.13, matching the real C API behavior on 3.13+. Simplify getattr_opt to use the compat function unconditionally, removing the #[cfg] branching.
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The
#[cfg(not(Py_3_13))]fallback path ofgetattr_optused.is()(type identity) to check whether an error wasAttributeError. This missesAttributeErrorsubclasses — they get propagated as errors instead of being treated as "attribute not found".On Python 3.13+,
PyObject_GetOptionalAttrinternally usesPyErr_ExceptionMatcheswhich does a proper subclass check, so this inconsistency only affects Python < 3.13.This PR replaces
.is()with.is_subclass_of::<PyAttributeError>()to match the 3.13+ semantics, and adds a test covering the case.Closes #5984
Discovered via pydantic/pydantic#13092 — pydantic's
from_attributes=Trueregressed on Python 3.12 after switching from a hand-rolledgetattrwrapper (which did subclass checking) to PyO3'sgetattr_opt.