dlr branch fix - Propagate exceptions from TryGetMember in tp_getattro_dlr_proxy#2718
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The dynamic getter swallowed any exception from TryGetMember and returned default to Python with the prior AttributeError still set, so user code observed a misleading AttributeError instead of the real failure. Set a Python exception in the catch arm. We use RuntimeError with the message string rather than Converter.ToPython(e) because wrapping the CLR exception object can trigger type initialisation that re-enters this same slot on the live dynamic object, producing infinite recursion. Mirrors the symmetry already present in the setter (pythonnet#2706 review, @lostmsu) and adds a regression test alongside the existing ThrowingSetDynamicObject coverage.
filmor
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May 12, 2026
The dynamic getter swallowed any exception from TryGetMember and returned default to Python with the prior AttributeError still set, so user code observed a misleading AttributeError instead of the real failure. Set a Python exception in the catch arm. We use RuntimeError with the message string rather than Converter.ToPython(e) because wrapping the CLR exception object can trigger type initialisation that re-enters this same slot on the live dynamic object, producing infinite recursion. Mirrors the symmetry already present in the setter (#2706 review, @lostmsu) and adds a regression test alongside the existing ThrowingSetDynamicObject coverage.
filmor
pushed a commit
that referenced
this pull request
May 12, 2026
The dynamic getter swallowed any exception from TryGetMember and returned default to Python with the prior AttributeError still set, so user code observed a misleading AttributeError instead of the real failure. Set a Python exception in the catch arm. We use RuntimeError with the message string rather than Converter.ToPython(e) because wrapping the CLR exception object can trigger type initialisation that re-enters this same slot on the live dynamic object, producing infinite recursion. Mirrors the symmetry already present in the setter (#2706 review, @lostmsu) and adds a regression test alongside the existing ThrowingSetDynamicObject coverage.
filmor
pushed a commit
that referenced
this pull request
May 13, 2026
The dynamic getter swallowed any exception from TryGetMember and returned default to Python with the prior AttributeError still set, so user code observed a misleading AttributeError instead of the real failure. Set a Python exception in the catch arm. We use RuntimeError with the message string rather than Converter.ToPython(e) because wrapping the CLR exception object can trigger type initialisation that re-enters this same slot on the live dynamic object, producing infinite recursion. Mirrors the symmetry already present in the setter (#2706 review, @lostmsu) and adds a regression test alongside the existing ThrowingSetDynamicObject coverage.
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Adds the symmetric exception-propagation fix to the DLR getter, completing the fix called out by @lostmsu in the #2706 review.
Problem
tp_getattro_dlr_proxyswallowed exceptions raised fromTryGetMemberand returneddefaultto Python while the priorAttributeErrorfromPyObject_GenericGetAttrwas still set. Callers therefore observed a misleadingAttributeErrorinstead of the real failure — exactly the kind of silent error-masking the reviewer flagged for the setter (which was fixed in d629b87).Fix
Set a Python exception in the catch block before returning
default.We use
Exceptions.SetError(Exceptions.RuntimeError, e.Message)rather thanExceptions.SetError(e)deliberately. Wrapping the CLR exception object viaConverter.ToPythontriggers CLR type initialisation, which can re-entertp_getattro_dlr_proxyon the same live dynamic object and recurse infinitely. A plainRuntimeErrorwith the message string preserves the diagnostic information without that hazard.Test
Adds
ThrowingGetDynamicObjecttodlrtest.csandtest_trygetmember_exception_is_raised_in_pythontotests/test_dynamic.py, mirroring the existing coverage forTrySetMember/TryDeleteMemberexception paths.