cmd/test2json: fix processing of --- BENCH: output

If a benchmark calls b.Log without failing (without b.Error/b.Fatal/b.FailNow)
then that turns into output very much like a test passing,
except it says BENCH instead of PASS.
Benchmarks failing say FAIL just like tests failing.

Fixes #23346.

Change-Id: Ib188e695952da78057ab4a13f90d49937aa3c232
Reviewed-on: https://go-review.googlesource.com/86396
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/cmd/internal/test2json/test2json.go

@@ -140,6 +140,7 @@ var (
 		[]byte("--- PASS: "),
 		[]byte("--- FAIL: "),
 		[]byte("--- SKIP: "),
+		[]byte("--- BENCH: "),
 	}
 
 	fourSpace = []byte("    ")
@@ -186,6 +187,7 @@ func (c *converter) handleInputLine(line []byte) {
 		// "--- PASS: "
 		// "--- FAIL: "
 		// "--- SKIP: "
+		// "--- BENCH: "
 		// but possibly indented.
 		for bytes.HasPrefix(line, fourSpace) {
 			line = line[4:]
@@ -206,8 +208,12 @@ func (c *converter) handleInputLine(line []byte) {
 	}
 
 	// Parse out action and test name.
-	action := strings.ToLower(strings.TrimSuffix(strings.TrimSpace(string(line[4:4+6])), ":"))
-	name := strings.TrimSpace(string(line[4+6:]))
+	i := bytes.IndexByte(line, ':') + 1
+	if i == 0 {
+		i = len(updates[0])
+	}
+	action := strings.ToLower(strings.TrimSuffix(strings.TrimSpace(string(line[4:i])), ":"))
+	name := strings.TrimSpace(string(line[i:]))
 
 	e := &event{Action: action}
 	if line[0] == '-' { // PASS or FAIL report

src/cmd/internal/test2json/testdata/bench.json

+{"Action":"output","Output":"goos: darwin\n"}
+{"Action":"output","Output":"goarch: 386\n"}
+{"Action":"output","Output":"BenchmarkFoo-8   \t2000000000\t         0.00 ns/op\n"}
+{"Action":"output","Test":"BenchmarkFoo-8","Output":"--- BENCH: BenchmarkFoo-8\n"}
+{"Action":"output","Test":"BenchmarkFoo-8","Output":"\tx_test.go:8: My benchmark\n"}
+{"Action":"output","Test":"BenchmarkFoo-8","Output":"\tx_test.go:8: My benchmark\n"}
+{"Action":"output","Test":"BenchmarkFoo-8","Output":"\tx_test.go:8: My benchmark\n"}
+{"Action":"output","Test":"BenchmarkFoo-8","Output":"\tx_test.go:8: My benchmark\n"}
+{"Action":"output","Test":"BenchmarkFoo-8","Output":"\tx_test.go:8: My benchmark\n"}
+{"Action":"output","Test":"BenchmarkFoo-8","Output":"\tx_test.go:8: My benchmark\n"}
+{"Action":"bench","Test":"BenchmarkFoo-8"}
+{"Action":"output","Output":"PASS\n"}
+{"Action":"output","Output":"ok  \tcommand-line-arguments\t0.009s\n"}
+{"Action":"pass"}

src/cmd/internal/test2json/testdata/bench.test

+goos: darwin
+goarch: 386
+BenchmarkFoo-8   	2000000000	         0.00 ns/op
+--- BENCH: BenchmarkFoo-8
+	x_test.go:8: My benchmark
+	x_test.go:8: My benchmark
+	x_test.go:8: My benchmark
+	x_test.go:8: My benchmark
+	x_test.go:8: My benchmark
+	x_test.go:8: My benchmark
+PASS
+ok  	command-line-arguments	0.009s

src/cmd/internal/test2json/testdata/benchfail.json

+{"Action":"output","Test":"BenchmarkFoo","Output":"--- FAIL: BenchmarkFoo\n"}
+{"Action":"output","Test":"BenchmarkFoo","Output":"\tx_test.go:8: My benchmark\n"}
+{"Action":"fail","Test":"BenchmarkFoo"}
+{"Action":"output","Output":"FAIL\n"}
+{"Action":"output","Output":"FAIL\tcommand-line-arguments\t0.008s\n"}
+{"Action":"fail"}

src/cmd/internal/test2json/testdata/benchfail.test

+--- FAIL: BenchmarkFoo
+	x_test.go:8: My benchmark
+FAIL
+FAIL	command-line-arguments	0.008s

src/cmd/test2json/main.go

@@ -45,7 +45,8 @@
 //	pause  - the test has been paused
 //	cont   - the test has continued running
 //	pass   - the test passed
-//	fail   - the test failed
+//	bench  - the benchmark printed log output but did not fail
+//	fail   - the test or benchmark failed
 //	output - the test printed output
 //
 // The Package field, if present, specifies the package being tested.
@@ -53,7 +54,7 @@
 // different tests are interlaced; the Package field allows readers to
 // separate them.
 //
-// The Test field, if present, specifies the test or example, or benchmark
+// The Test field, if present, specifies the test, example, or benchmark
 // function that caused the event. Events for the overall package test
 // do not set Test.
 //
@@ -67,6 +68,14 @@
 // the concatenation of the Output fields of all output events is the exact
 // output of the test execution.
 //
+// When a benchmark runs, it typically produces a single line of output
+// giving timing results. That line is reported in an event with Action == "output"
+// and no Test field. If a benchmark logs output or reports a failure
+// (for example, by using b.Log or b.Error), that extra output is reported
+// as a sequence of events with Test set to the benchmark name, terminated
+// by a final event with Action == "bench" or "fail".
+// Benchmarks have no events with Action == "run", "pause", or "cont".
+//
 package main
 
 import (