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test(lsp): wait for a killed server before reading its goroutine dump #607

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Merged
HuiJun merged 1 commit into from
Sep 26, 2026
+11 −2
Merged

test(lsp): wait for a killed server before reading its goroutine dump #607

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1 change: 1 addition & 0 deletions changes/unreleased/lsp-silent-server-stderr.fixed.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
- **The language-server lifecycle tests wait for a killed server before reading its stderr.** `TestSilentServerFailsWithinDeadline` read the captured stderr as soon as the server's stdout closed, before `os/exec` had finished copying the goroutine dump the `SIGQUIT` produced, so the dump was sometimes empty and the test failed at random under load.
12 changes: 10 additions & 2 deletions cmd/sysml-lsp/lifecycle_test.go
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Expand Up @@ -163,7 +163,7 @@ func (s *session) readBy(deadline time.Time) map[string]any {
line, err := s.stdout.ReadString('\n')
if err != nil {
if s.killed.Load() {
s.fail("read header: %v (server killed after %s of silence)\nstderr: %s", err, time.Since(start).Round(time.Millisecond), s.stderr.String())
s.fail("read header: %v (server killed after %s of silence)\nstderr: %s", err, time.Since(start).Round(time.Millisecond), s.killedStderr())
} else {
s.fail("read header: %v\nstderr: %s", err, s.stderr.String())
}
Expand Down Expand Up @@ -193,7 +193,7 @@ func (s *session) readBy(deadline time.Time) map[string]any {
body := make([]byte, length)
if _, err := io.ReadFull(s.stdout, body); err != nil {
if s.killed.Load() {
s.fail("read body: %v (server killed after %s of silence)\nstderr: %s", err, time.Since(start).Round(time.Millisecond), s.stderr.String())
s.fail("read body: %v (server killed after %s of silence)\nstderr: %s", err, time.Since(start).Round(time.Millisecond), s.killedStderr())
} else {
s.fail("read body: %v", err)
}
Expand Down Expand Up @@ -224,6 +224,14 @@ func (s *session) dumpAndKill() {
time.AfterFunc(5*time.Second, func() { _ = s.cmd.Process.Kill() })
}

// killedStderr returns everything a killed server wrote to stderr, goroutine dump
// included: os/exec finishes copying the pipe into cmd.Stderr only in Wait.
func (s *session) killedStderr() string {
s.t.Helper()
s.waitStatus(10 * time.Second)
return s.stderr.String()
}

// waitStatus waits for the process to end and returns its exit status. A server
// still running when the timeout expires is a leaked server, and a failure.
func (s *session) waitStatus(timeout time.Duration) int {
Expand Down
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