165121e53eThe "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 - typically `io.EOF` when 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 via
`errors.Is(err, io.EOF)` therefore always got `false`.
This changes both `s.writeErr` wrappings 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 `shuttingDown`
and asserts both `errors.Is(err, ErrServerClosing)` and `errors.Is(err,
io.EOF)`.
Fixes #1098
---------
Co-authored-by: Bo Zhang <187063395+Tethys0@users.noreply.github.com>
Co-authored-by: Guglielmo Colombo <guglielmoc@google.com>
38 lines
1.2 KiB
Go
38 lines
1.2 KiB
Go
// Copyright 2025 The Go MCP SDK Authors. All rights reserved.
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// Use of this source code is governed by the license
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// that can be found in the LICENSE file.
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package jsonrpc2
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import (
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"errors"
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"io"
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"testing"
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)
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// TestShuttingDownWrapsWriteError verifies that when a connection shuts down
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// because its write side failed, the returned error preserves the underlying
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// write error in its chain so callers can classify it with errors.Is (for
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// example, distinguishing io.EOF from a clean host disconnect versus a real
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// failure).
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func TestShuttingDownWrapsWriteError(t *testing.T) {
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s := &inFlightState{writeErr: io.EOF}
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err := s.shuttingDown(ErrServerClosing)
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if !errors.Is(err, ErrServerClosing) {
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t.Errorf("shuttingDown() error = %v, want it to wrap ErrServerClosing", err)
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}
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if !errors.Is(err, io.EOF) {
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t.Errorf("shuttingDown() error = %v, want it to wrap io.EOF", err)
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}
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}
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func TestShuttingDownWrapsReadError(t *testing.T) {
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s := &inFlightState{readErr: io.EOF}
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err := s.shuttingDown(ErrServerClosing)
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if !errors.Is(err, ErrServerClosing) {
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t.Errorf("shuttingDown() error = %v, want it to wrap ErrServerClosing", err)
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}
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if !errors.Is(err, io.EOF) {
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t.Errorf("shuttingDown() error = %v, want it to wrap io.EOF", err)
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}
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}
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