cmd/test2json: benchmark --- BENCH output not handled

[zolotov]

While running benchmarks, the output is poor-structured. Would be nice to have start and passed events. Skip and Failed events work fine.

~/dev/go/bin/go test -bench=. -json benchmark_test.go

{"Time":"2018-01-05T12:38:47.961012155+03:00","Action":"output","Package":"command-line-arguments","Output":"goos: darwin\n"}
{"Time":"2018-01-05T12:38:47.961389758+03:00","Action":"output","Package":"command-line-arguments","Output":"goarch: amd64\n"}
{"Time":"2018-01-05T12:38:47.96164686+03:00","Action":"output","Package":"command-line-arguments","Output":"BenchmarkFoo-4   \t2000000000\t         0.00 ns/op\n"}
{"Time":"2018-01-05T12:38:47.961683819+03:00","Action":"output","Package":"command-line-arguments","Output":"--- BENCH: BenchmarkFoo-4\n"}
{"Time":"2018-01-05T12:38:47.961696276+03:00","Action":"output","Package":"command-line-arguments","Output":"\tbenchmark_test.go:8: My benchmark\n"}
{"Time":"2018-01-05T12:38:47.96170952+03:00","Action":"output","Package":"command-line-arguments","Output":"\tbenchmark_test.go:8: My benchmark\n"}
{"Time":"2018-01-05T12:38:47.961714862+03:00","Action":"output","Package":"command-line-arguments","Output":"\tbenchmark_test.go:8: My benchmark\n"}
{"Time":"2018-01-05T12:38:47.961719489+03:00","Action":"output","Package":"command-line-arguments","Output":"\tbenchmark_test.go:8: My benchmark\n"}
{"Time":"2018-01-05T12:38:47.961723798+03:00","Action":"output","Package":"command-line-arguments","Output":"\tbenchmark_test.go:8: My benchmark\n"}
{"Time":"2018-01-05T12:38:47.961731677+03:00","Action":"output","Package":"command-line-arguments","Output":"\tbenchmark_test.go:8: My benchmark\n"}
{"Time":"2018-01-05T12:38:47.961738298+03:00","Action":"output","Package":"command-line-arguments","Output":"PASS\n"}
{"Time":"2018-01-05T12:38:47.962676143+03:00","Action":"output","Package":"command-line-arguments","Output":"ok  \tcommand-line-arguments\t0.009s\n"}
{"Time":"2018-01-05T12:38:47.962695242+03:00","Action":"pass","Package":"command-line-arguments","Elapsed":0.009}

package benchmark

import (
	"testing"
)

func BenchmarkFoo(b *testing.B) {
	b.Log("My benchmark")
}

[ianlancetaylor]

CC @rsc

[rsc]

The test2json event definition has no answer for benchmarks generally. Benchmark timing output (the leading BenchmarkFoo line that benchstat reads) probably will be treated as ordinary top-level output here.

The --- BENCH: output that shows b.Log output we can definitely process and json-ify as if it were a test. I'll do that.

[rsc]

Filed #23352 for benchmark start events.

[gopherbot]

Change https://golang.org/cl/86396 mentions this issue: cmd/test2json: fix processing of --- BENCH: output