jsonrpc2: wrap write error in server-closing error - #1186
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guglielmo-san merged 4 commits intoAug 27, 2026
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The connection's "server is closing" error formatted the underlying write error with %v, so the cause - typically io.EOF when a stdio host closes its pipe - was not in the error chain. Callers using errors.Is(err, io.EOF) to distinguish a clean host disconnect from a real failure therefore always got false. Use %w so the write error is preserved in the error chain. Fixes modelcontextprotocol#1098
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we should use the same approach for both cases
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Applied the same %w wrapping to the read-shutdown path in aecb26d, with a focused errors.Is regression test. The pushed branch is ready for re-review.
guglielmo-san
previously approved these changes
Aug 26, 2026
guglielmo-san
enabled auto-merge (squash)
August 27, 2026 12:46
nahapetyan-serob
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Aug 27, 2026
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The "server is closing" error produced when a connection shuts down because its write side failed formatted the underlying write error with
%v, so the cause - typicallyio.EOFwhen a stdio host closes its pipe - was not part of the error chain. A caller that wants to distinguish a clean host disconnect from a real failure viaerrors.Is(err, io.EOF)therefore always gotfalse.This changes both
s.writeErrwrappings to use%w, preserving the write error in the error chain while keeping the same message text ("server is closing: EOF").A regression test exercises the write-failure branch of
shuttingDownand asserts botherrors.Is(err, ErrServerClosing)anderrors.Is(err, io.EOF).Fixes #1098