internal/trace: fix recorder.Write return value for header-only buffers

jjpinto · Go LUCI · commit d1e7f49e3d1e · 2026-01-07T12:07:56.000-08:00
Fix issue #77083 Change-Id: I9189d1e3a6efea8478224164e820f50c818abcd5 GitHub-Last-Rev: bb24cbd GitHub-Pull-Request: #77092 Reviewed-on: https://go-review.googlesource.com/c/go/+/734300 Reviewed-by: Michael Pratt <mpratt@google.com> Reviewed-by: Michael Knyszek <mknyszek@google.com> Commit-Queue: Michael Knyszek <mknyszek@google.com> LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
diff --git a/src/runtime/trace/recorder.go b/src/runtime/trace/recorder.go
@@ -39,7 +39,7 @@ func (w *recorder) Write(b []byte) (n int, err error) {
 		w.headerReceived = true
 	}
 	if len(b) == n {
-		return 0, nil
+		return n, nil
 	}
 	ba, nb, err := readBatch(b[n:]) // Every write from the runtime is guaranteed to be a complete batch.
 	if err != nil {

Original file line number	Diff line number	Diff line change
`@@ -39,7 +39,7 @@ func (w *recorder) Write(b []byte) (n int, err error) {`
`39`	`39`	`w.headerReceived = true`
`40`	`40`	`}`
`41`	`41`	`if len(b) == n {`
`42`		`- return 0, nil`
	`42`	`+ return n, nil`
`43`	`43`	`}`
`44`	`44`	`ba, nb, err := readBatch(b[n:]) // Every write from the runtime is guaranteed to be a complete batch.`
`45`	`45`	`if err != nil {`