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dlr branch fix - Propagate exceptions from TryGetMember in tp_getattro_dlr_proxy - #2718
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filmor merged 1 commit intoMay 11, 2026
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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.
filmor
pushed a commit
that referenced
this pull request
May 15, 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_proxy swallowed exceptions raised from TryGetMember and returned default to Python while the prior AttributeError from PyObject_GenericGetAttr was still set. Callers therefore observed a misleading AttributeError instead 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 than Exceptions.SetError(e) deliberately. Wrapping the CLR exception object via Converter.ToPython triggers CLR type initialisation, which can re-enter tp_getattro_dlr_proxy on the same live dynamic object and recurse infinitely. A plain RuntimeError with the message string preserves the diagnostic information without that hazard.
Test
Adds ThrowingGetDynamicObject to dlrtest.cs and test_trygetmember_exception_is_raised_in_python to tests/test_dynamic.py, mirroring the existing coverage for TrySetMember/TryDeleteMember exception paths.