cmd/go: ensure streaming test's stdout, stderr are same as cmd/go's

Fixes #18153

Change-Id: Ie8a32dd6fe306f00e51cde77dd4ea353f7109940
Reviewed-on: https://go-review.googlesource.com/34010
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/cmd/dist/test.go

@@ -15,6 +15,7 @@ import (
 	"os/exec"
 	"path/filepath"
 	"regexp"
+	"runtime"
 	"strconv"
 	"strings"
 	"sync"
@@ -331,6 +332,10 @@ func (t *tester) registerRaceBenchTest(pkg string) {
 	})
 }
 
+// stdOutErrAreTerminals is defined in test_linux.go, to report
+// whether stdout & stderr are terminals.
+var stdOutErrAreTerminals func() bool
+
 func (t *tester) registerTests() {
 	if strings.HasSuffix(os.Getenv("GO_BUILDER_NAME"), "-vetall") {
 		// Run vet over std and cmd and call it quits.
@@ -347,6 +352,27 @@ func (t *tester) registerTests() {
 		return
 	}
 
+	// This test needs its stdout/stderr to be terminals, so we don't run it from cmd/go's tests.
+	// See issue 18153.
+	if runtime.GOOS == "linux" {
+		t.tests = append(t.tests, distTest{
+			name:    "cmd_go_test_terminal",
+			heading: "cmd/go terminal test",
+			fn: func(dt *distTest) error {
+				t.runPending(dt)
+				if !stdOutErrAreTerminals() {
+					fmt.Println("skipping terminal test; stdout/stderr not terminals")
+					return nil
+				}
+				cmd := exec.Command("go", "test")
+				cmd.Dir = filepath.Join(os.Getenv("GOROOT"), "src/cmd/go/testdata/testterminal18153")
+				cmd.Stdout = os.Stdout
+				cmd.Stderr = os.Stderr
+				return cmd.Run()
+			},
+		})
+	}
+
 	// Fast path to avoid the ~1 second of `go list std cmd` when
 	// the caller lists specific tests to run. (as the continuous
 	// build coordinator does).

src/cmd/dist/test_linux.go

@@ -0,0 +1,27 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build linux
+
+package main
+
+import (
+	"syscall"
+	"unsafe"
+)
+
+const ioctlReadTermios = syscall.TCGETS
+
+// isTerminal reports whether fd is a terminal.
+func isTerminal(fd uintptr) bool {
+	var termios syscall.Termios
+	_, _, err := syscall.Syscall6(syscall.SYS_IOCTL, fd, ioctlReadTermios, uintptr(unsafe.Pointer(&termios)), 0, 0, 0)
+	return err == 0
+}
+
+func init() {
+	stdOutErrAreTerminals = func() bool {
+		return isTerminal(1) && isTerminal(2)
+	}
+}

src/cmd/go/test.go

@@ -13,7 +13,6 @@ import (
 	"go/doc"
 	"go/parser"
 	"go/token"
-	"io"
 	"os"
 	"os/exec"
 	"path"
@@ -1122,12 +1121,8 @@ func (b *builder) runTest(a *action) error {
 	cmd.Env = envForDir(cmd.Dir, origEnv)
 	var buf bytes.Buffer
 	if testStreamOutput {
-		// The only way to keep the ordering of the messages and still
-		// intercept its contents. os/exec will share the same Pipe for
-		// both Stdout and Stderr when running the test program.
-		mw := io.MultiWriter(os.Stdout, &buf)
-		cmd.Stdout = mw
-		cmd.Stderr = mw
+		cmd.Stdout = os.Stdout
+		cmd.Stderr = os.Stderr
 	} else {
 		cmd.Stdout = &buf
 		cmd.Stderr = &buf
@@ -1192,7 +1187,7 @@ func (b *builder) runTest(a *action) error {
 	t := fmt.Sprintf("%.3fs", time.Since(t0).Seconds())
 	if err == nil {
 		norun := ""
-		if testShowPass && !testStreamOutput {
+		if testShowPass {
 			a.testOutput.Write(out)
 		}
 		if bytes.HasPrefix(out, noTestsToRun[1:]) || bytes.Contains(out, noTestsToRun) {
@@ -1204,9 +1199,7 @@ func (b *builder) runTest(a *action) error {
 
 	setExitStatus(1)
 	if len(out) > 0 {
-		if !testStreamOutput {
-			a.testOutput.Write(out)
-		}
+		a.testOutput.Write(out)
 		// assume printing the test binary's exit status is superfluous
 	} else {
 		fmt.Fprintf(a.testOutput, "%s\n", err)

src/cmd/go/testdata/testterminal18153/terminal_test.go

@@ -0,0 +1,39 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build linux
+
+// This test is run by src/cmd/dist/test.go (cmd_go_test_terminal),
+// and not by cmd/go's tests. This is because this test requires that
+// that it be called with its stdout and stderr being a terminal.
+// dist doesn't run `cmd/go test` against this test directory if
+// dist's stdout/stderr aren't terminals.
+//
+// See issue 18153.
+
+package p
+
+import (
+	"syscall"
+	"testing"
+	"unsafe"
+)
+
+const ioctlReadTermios = syscall.TCGETS
+
+// isTerminal reports whether fd is a terminal.
+func isTerminal(fd uintptr) bool {
+	var termios syscall.Termios
+	_, _, err := syscall.Syscall6(syscall.SYS_IOCTL, fd, ioctlReadTermios, uintptr(unsafe.Pointer(&termios)), 0, 0, 0)
+	return err == 0
+}
+
+func TestIsTerminal(t *testing.T) {
+	if !isTerminal(1) {
+		t.Errorf("stdout is not a terminal")
+	}
+	if !isTerminal(2) {
+		t.Errorf("stderr is not a terminal")
+	}
+}