cmd/go: go test -json has non-JSON printed to stdout when build fails

[ailurarctos]

What version of Go are you using (go version)?

$ go version
go version go1.13.3 linux/amd64

Does this issue reproduce with the latest release?

Yes.

What operating system and processor architecture are you using (go env)?

go env Output

$ go env
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/me/.cache/go-build"
GOENV="/home/me/.config/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/home/me/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/lib/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/lib/go/pkg/tool/linux_amd64"
GCCGO="gccgo"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/home/me/example.com/go.mod"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build779567786=/tmp/go-build -gno-record-gcc-switches"
GOROOT/bin/go version: go version go1.13.3 linux/amd64
GOROOT/bin/go tool compile -V: compile version go1.13.3
uname -sr: Linux 5.3.7-arch1-1-ARCH
/usr/lib/libc.so.6: GNU C Library (GNU libc) stable release version 2.30.

What did you do?

Run go test -json when a package has a build failure. Here is my example_test.go:

package example

import "testing"

func Test(t *testing.T) {
	broken
}

What did you expect to see?

I expected to see JSON events similar to when a package is skipped because it has no tests. Here is an example:

{"Time":"2019-10-26T09:09:27.272054198+09:00","Action":"output","Package":"example.com","Output":"FAIL\texample.com [build failed]\n"}
{"Time":"2019-10-26T09:09:27.272173706+09:00","Action":"fail","Package":"example.com","Elapsed":0}

What did you see instead?

The package result is printed as-is to stdout:

example.com]$ go test -json 2>/dev/null
FAIL	example.com [build failed]

[ailurarctos]

This issue might be related to (or a duplicate of) #23037 but I'm not sure because that ticket seems to ask for -json support in go build. What I'm hoping for is to not have go test -json print non-JSON to stdout.

[dmitshur]

/cc @bcmills @jayconrod

[rsc]

For now I believe the rule is that stdout gets JSON and stderr gets non-JSON.
It sounds like there is a FAIL line printed to stdout that should be JSON'ed.

We should probably open a separate issue for structuring go build's failures (go build -json?) and then we'd just enable it during go test -json too.

[gopherbot]

Change https://go.dev/cl/529120 mentions this issue: cmd/go: avoid writing non-JSON "build failed" errors from 'go test -json'