3 files changed, 37 insertions, 0 deletions
diff --git a/src/cmd/internal/test2json/test2json.go b/src/cmd/internal/test2json/test2json.go
index fa0708357b..483fb1de52 100644
--- a/src/cmd/internal/test2json/test2json.go
+++ b/src/cmd/internal/test2json/test2json.go
@@ -16,6 +16,7 @@ import (
 	"strconv"
 	"strings"
 	"time"
+	"unicode"
 	"unicode/utf8"
 )
 
@@ -349,6 +350,15 @@ func (l *lineBuffer) write(b []byte) {
 		for i < len(l.b) {
 			j := bytes.IndexByte(l.b[i:], '\n')
 			if j < 0 {
+				if !l.mid {
+					if j := bytes.IndexByte(l.b[i:], '\t'); j >= 0 {
+						if isBenchmarkName(bytes.TrimRight(l.b[i:i+j], " ")) {
+							l.part(l.b[i : i+j+1])
+							l.mid = true
+							i += j + 1
+						}
+					}
+				}
 				break
 			}
 			e := i + j + 1
@@ -390,6 +400,21 @@ func (l *lineBuffer) flush() {
 	}
 }
 
+var benchmark = []byte("Benchmark")
+
+// isBenchmarkName reports whether b is a valid benchmark name
+// that might appear as the first field in a benchmark result line.
+func isBenchmarkName(b []byte) bool {
+	if !bytes.HasPrefix(b, benchmark) {
+		return false
+	}
+	if len(b) == len(benchmark) { // just "Benchmark"
+		return true
+	}
+	r, _ := utf8.DecodeRune(b[len(benchmark):])
+	return !unicode.IsLower(r)
+}
+
 // trimUTF8 returns a length t as close to len(b) as possible such that b[:t]
 // does not end in the middle of a possibly-valid UTF-8 sequence.
 //
diff --git a/src/cmd/internal/test2json/testdata/benchshort.json b/src/cmd/internal/test2json/testdata/benchshort.json
new file mode 100644
index 0000000000..8c61d95d8d
--- /dev/null
+++ b/src/cmd/internal/test2json/testdata/benchshort.json
@@ -0,0 +1,7 @@
+{"Action":"output","Output":"# This file ends in an early EOF to trigger the Benchmark prefix test,\n"}
+{"Action":"output","Output":"# which only happens when a benchmark prefix is seen ahead of the \\n.\n"}
+{"Action":"output","Output":"# Normally that's due to the benchmark running and the \\n coming later,\n"}
+{"Action":"output","Output":"# but to avoid questions of timing, we just use a file with no \\n at all.\n"}
+{"Action":"output","Output":"BenchmarkFoo   \t"}
+{"Action":"output","Output":"10000 early EOF"}
+{"Action":"fail"}
diff --git a/src/cmd/internal/test2json/testdata/benchshort.test b/src/cmd/internal/test2json/testdata/benchshort.test
new file mode 100644
index 0000000000..0b173ab20d
--- /dev/null
+++ b/src/cmd/internal/test2json/testdata/benchshort.test
@@ -0,0 +1,5 @@
+# This file ends in an early EOF to trigger the Benchmark prefix test,
+# which only happens when a benchmark prefix is seen ahead of the \n.
+# Normally that's due to the benchmark running and the \n coming later,
+# but to avoid questions of timing, we just use a file with no \n at all.
+BenchmarkFoo   	10000 early EOF
+\ No newline at end of file