Fix stdio_client BrokenResourceError race condition during shutdown#2268
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weiguangli-io wants to merge 1 commit intomodelcontextprotocol:mainfrom
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Fix stdio_client BrokenResourceError race condition during shutdown#2268weiguangli-io wants to merge 1 commit intomodelcontextprotocol:mainfrom
weiguangli-io wants to merge 1 commit intomodelcontextprotocol:mainfrom
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During shutdown, the finally block closes the receiving end of the read_stream memory channel while stdout_reader may still be blocked on send(). This causes BrokenResourceError (not ClosedResourceError) because the *other* end of the stream was closed. The existing except clause only caught ClosedResourceError, letting BrokenResourceError propagate into an ExceptionGroup. Catch BrokenResourceError alongside ClosedResourceError in both stdout_reader and stdin_writer to handle this race gracefully. Closes modelcontextprotocol#1960 Github-Issue:modelcontextprotocol#1960 Reported-by:maxisbey
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Summary
Fixes #1960. Supersedes #2219 (which was closed).
During
stdio_clientshutdown, thefinallyblock closesread_stream(the receiving end of a zero-buffer memory channel) whilestdout_readermay still be blocked onsend(). When the receiving end closes underneath a pendingsend(), anyio raisesBrokenResourceError— notClosedResourceError. The existingexceptclause only caughtClosedResourceError, soBrokenResourceErrorescaped into anExceptionGroup.The fix catches
BrokenResourceErroralongsideClosedResourceErrorin bothstdout_readerandstdin_writer. This is the minimal, correct change:ClosedResourceErrormeans "you called send on a handle you already closed", whileBrokenResourceErrormeans "the other end was closed" — both are expected during shutdown and should be handled identically.Test plan
test_stdio_client_no_broken_resource_error_on_shutdownthat reproduces the exact scenario: server sends a JSON-RPC message, client exits without consuming the read streamtests/client/test_stdio.pytests pass