cmd/go: add build -json, to report build failures in JSON

[zolotov]

If I run go test on a directory and one of the packages is failed to run, I won't get any json output for it.
It would be great to have at least a single package-fail json-message.

[ianlancetaylor]

In general the go tool does not support multiple packages in a single directory.

Can you give a small complete example?

[zolotov]

• dir/compilablePackage/foo_test.go
• dir/nonCompilablePackage/foo_test.go

run cd dir && go test -json ./...

[ianlancetaylor]

Thanks. For future reference, when I ask for a small complete example, it really helps a lot if you can give a complete example, which means the exact files and the exact commands. Otherwise I have to guess what you mean when you say "nonCompilablePackage", and experience tells me that I often guess wrong.

Here is a complete example that may show the problem:

src/p1/p1.go

package p1

func F() {}

src/p1/p1_test.go

package p1

import "testing"

func TestF(t *testing.T) {
	F()
	t.Log("F")
}

src/p2/p2.go:

package p2

func F() {}

this file will not compile

src/p2/p2_test.go:

package p2

import "testing"

func TestF(t *testing.T) {
	F()
	t.Log("F")
}

go test -json ./...

# p2
src/p2/p2.go:5:1: syntax error: non-declaration statement outside function body
{"Time":"2017-12-15T13:38:12.885932037-08:00","Action":"run","Package":"p1","Test":"TestF"}
{"Time":"2017-12-15T13:38:12.886027694-08:00","Action":"output","Package":"p1","Test":"TestF","Output":"=== RUN   TestF\n"}
{"Time":"2017-12-15T13:38:12.88604052-08:00","Action":"output","Package":"p1","Test":"TestF","Output":"--- PASS: TestF (0.00s)\n"}
{"Time":"2017-12-15T13:38:12.886047376-08:00","Action":"output","Package":"p1","Test":"TestF","Output":"\tp1_test.go:7: F\n"}
{"Time":"2017-12-15T13:38:12.886054374-08:00","Action":"pass","Package":"p1","Test":"TestF","Elapsed":0}
{"Time":"2017-12-15T13:38:12.88607203-08:00","Action":"output","Package":"p1","Output":"PASS\n"}
{"Time":"2017-12-15T13:38:12.886112826-08:00","Action":"output","Package":"p1","Output":"ok  \tp1\t0.009s\n"}
{"Time":"2017-12-15T13:38:12.886135226-08:00","Action":"pass","Package":"p1","Elapsed":0.009}
FAIL	p2 [build failed]

If I understand you correctly, you are saying that you would like to have JSON output that reports that we were unable to build package p2. Is that correct?

CC @rsc

[zolotov]

Yes, that's correct.

[rsc]

You're asking for go build -json. We are only adding go test -json in this release. Maybe in a future release we could add go build -json and make go test imply that flag. Sorry.