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

Fix issue #77083

Change-Id: I9189d1e3a6efea8478224164e820f50c818abcd5
GitHub-Last-Rev: bb24cbda95f0b5b10aeae9a5ee8cbe215ba6d4eb
GitHub-Pull-Request: golang/go#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
index 4f2d3aa92a412497a3b003736d32ae24c654ab5f..a18d764141b42f24ca00d78d2983af1ff45241b2 100644 (file)
--- 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 {