fix: Add cycle detection to exceptions_from_error#5880
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ericapisani wants to merge 4 commits intomasterfrom
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fix: Add cycle detection to exceptions_from_error#5880ericapisani wants to merge 4 commits intomasterfrom
ericapisani wants to merge 4 commits intomasterfrom
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When using FastAPI with multiple BaseHTTPMiddleware instances, anyio wraps exceptions in ExceptionGroups. When Starlette unpacks and reraises these, it creates cyclic references (ExceptionGroup -> ValueError -> __cause__ -> ExceptionGroup) that cause infinite recursion in exceptions_from_error(), silently dropping the event. Track seen exception object ids during recursive walks through __cause__, __context__, and ExceptionGroup.exceptions to break cycles. Fixes GH-5025 Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Replace test_cyclic_exception_group_context with test_exceptiongroup_starlette_collapse that simulates the actual collapse_excgroups() pattern from Starlette. This provides a more realistic regression test for the cycle detection in exceptions_from_error() by reproducing the exact __context__ cycle that occurs in production with FastAPI and multiple BaseHTTPMiddleware instances. Remove the now-redundant synthetic __context__ cycle test since the new test covers the same code path with a more representative scenario. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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Type seen_exceptions as Optional[list[BaseException]] instead of Optional[list] and split the None checks for seen_exceptions and seen_exception_ids so each parameter is independently initialized. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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Summary
exceptions_from_error()to prevent infinite recursion when exception chains contain cyclesBaseHTTPMiddlewareinstances cause Starlette'scollapse_excgroups()to create cyclic__context__references (ExceptionGroup → inner exception →__context__→ ExceptionGroup)RecursionErrorTest plan
test_exceptiongroup_starlette_collapse— realistic reproduction of the Starlettecollapse_excgroups()pattern with exact expected exception valuestest_cyclic_exception_group_cause— verifies cycle detection works for__cause__chainstest_deeply_nested_cyclic_exception_group— verifies cycle detection across multiple nested ExceptionGroupsFixes #5025 and PY-1949
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