all: correct location of go tool

In general, there are no guarantee that `go` command exist on $PATH.
This CL tries to get `go` command from $GOROOT/bin instead.

There are three kinds of code we should handle:
    For normal code, the CL implements goCmd() or goCmdName().
    For unit tests, the CL uses testenv.GoTool() or testenv.GoToolPath().
    For integration tests, the CL sets PATH=$GOROOT/bin:$PATH in cmd/dist.

Note that make.bash sets PATH=$GOROOT/bin:$PATH in the build process.
So this change is only useful when we use toolchain manually.

Updates #21875

Change-Id: I963b9f22ea732dd735363ececde4cf94a5db5ca2
Reviewed-on: https://go-review.googlesource.com/64650
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

7 files changed, 61 insertions, 8 deletions

diff --git a/src/cmd/api/goapi.go b/src/cmd/api/goapi.go
index 936f9e5511..8cc78c01ed 100644
--- a/src/cmd/api/goapi.go
+++ b/src/cmd/api/goapi.go
@@ -27,6 +27,18 @@ import (
 	"strings"
 )
 
+func goCmd() string {
+	var exeSuffix string
+	if runtime.GOOS == "windows" {
+		exeSuffix = ".exe"
+	}
+	path := filepath.Join(runtime.GOROOT(), "bin", "go"+exeSuffix)
+	if _, err := os.Stat(path); err == nil {
+		return path
+	}
+	return "go"
+}
+
 // Flags
 var (
 	checkFile  = flag.String("c", "", "optional comma-separated filename(s) to check API against")
@@ -127,7 +139,7 @@ func main() {
 	if flag.NArg() > 0 {
 		pkgNames = flag.Args()
 	} else {
-		stds, err := exec.Command("go", "list", "std").Output()
+		stds, err := exec.Command(goCmd(), "list", "std").Output()
 		if err != nil {
 			log.Fatal(err)
 		}
diff --git a/src/cmd/api/goapi_test.go b/src/cmd/api/goapi_test.go
index 0d00f6a297..3c4e50a21a 100644
--- a/src/cmd/api/goapi_test.go
+++ b/src/cmd/api/goapi_test.go
@@ -9,6 +9,7 @@ import (
 	"flag"
 	"fmt"
 	"go/build"
+	"internal/testenv"
 	"io/ioutil"
 	"os"
 	"os/exec"
@@ -163,7 +164,7 @@ func TestSkipInternal(t *testing.T) {
 }
 
 func BenchmarkAll(b *testing.B) {
-	stds, err := exec.Command("go", "list", "std").Output()
+	stds, err := exec.Command(testenv.GoToolPath(b), "list", "std").Output()
 	if err != nil {
 		b.Fatal(err)
 	}
diff --git a/src/cmd/api/run.go b/src/cmd/api/run.go
index 20cddb704b..219776cae4 100644
--- a/src/cmd/api/run.go
+++ b/src/cmd/api/run.go
@@ -14,8 +14,21 @@ import (
 	"os"
 	"os/exec"
 	"path/filepath"
+	"runtime"
 )
 
+func goCmd() string {
+	var exeSuffix string
+	if runtime.GOOS == "windows" {
+		exeSuffix = ".exe"
+	}
+	path := filepath.Join(runtime.GOROOT(), "bin", "go"+exeSuffix)
+	if _, err := os.Stat(path); err == nil {
+		return path
+	}
+	return "go"
+}
+
 var goroot string
 
 func main() {
@@ -25,7 +38,7 @@ func main() {
 		log.Fatal("No $GOROOT set.")
 	}
 
-	out, err := exec.Command("go", "tool", "api",
+	out, err := exec.Command(goCmd(), "tool", "api",
 		"-c", file("go1", "go1.1", "go1.2", "go1.3", "go1.4", "go1.5", "go1.6", "go1.7", "go1.8", "go1.9"),
 		"-next", file("next"),
 		"-except", file("except")).CombinedOutput()
diff --git a/src/cmd/dist/test.go b/src/cmd/dist/test.go
index e9b4ca0fb2..ae7f25cad9 100644
--- a/src/cmd/dist/test.go
+++ b/src/cmd/dist/test.go
@@ -85,6 +85,14 @@ type distTest struct {
 }
 
 func (t *tester) run() {
+	var exeSuffix string
+	if goos == "windows" {
+		exeSuffix = ".exe"
+	}
+	if _, err := os.Stat(filepath.Join(gobin, "go"+exeSuffix)); err == nil {
+		os.Setenv("PATH", fmt.Sprintf("%s%c%s", gobin, os.PathListSeparator, os.Getenv("PATH")))
+	}
+
 	slurp, err := exec.Command("go", "env", "CGO_ENABLED").Output()
 	if err != nil {
 		log.Fatalf("Error running go env CGO_ENABLED: %v", err)
diff --git a/src/cmd/go/go_test.go b/src/cmd/go/go_test.go
index eaa2d0f68d..1a47b72083 100644
--- a/src/cmd/go/go_test.go
+++ b/src/cmd/go/go_test.go
@@ -91,20 +91,25 @@ func TestMain(m *testing.M) {
 		if race.Enabled {
 			args = append(args, "-race")
 		}
-		out, err := exec.Command("go", args...).CombinedOutput()
+		gotool, err := testenv.GoTool()
+		if err != nil {
+			fmt.Fprintln(os.Stderr, err)
+			os.Exit(2)
+		}
+		out, err := exec.Command(gotool, args...).CombinedOutput()
 		if err != nil {
 			fmt.Fprintf(os.Stderr, "building testgo failed: %v\n%s", err, out)
 			os.Exit(2)
 		}
 
-		out, err = exec.Command("go", "env", "GOROOT").CombinedOutput()
+		out, err = exec.Command(gotool, "env", "GOROOT").CombinedOutput()
 		if err != nil {
 			fmt.Fprintf(os.Stderr, "could not find testing GOROOT: %v\n%s", err, out)
 			os.Exit(2)
 		}
 		testGOROOT = strings.TrimSpace(string(out))
 
-		out, err = exec.Command("go", "env", "CC").CombinedOutput()
+		out, err = exec.Command(gotool, "env", "CC").CombinedOutput()
 		if err != nil {
 			fmt.Fprintf(os.Stderr, "could not find testing CC: %v\n%s", err, out)
 			os.Exit(2)
diff --git a/src/cmd/link/internal/ld/nooptcgolink_test.go b/src/cmd/link/internal/ld/nooptcgolink_test.go
index 1df29652b2..e019a39bf7 100644
--- a/src/cmd/link/internal/ld/nooptcgolink_test.go
+++ b/src/cmd/link/internal/ld/nooptcgolink_test.go
@@ -22,7 +22,7 @@ func TestNooptCgoBuild(t *testing.T) {
 		t.Fatal(err)
 	}
 	defer os.RemoveAll(dir)
-	cmd := exec.Command("go", "build", "-gcflags=-N -l", "-o", filepath.Join(dir, "a.out"))
+	cmd := exec.Command(testenv.GoToolPath(t), "build", "-gcflags=-N -l", "-o", filepath.Join(dir, "a.out"))
 	cmd.Dir = filepath.Join(runtime.GOROOT(), "src", "runtime", "testdata", "testprogcgo")
 	out, err := cmd.CombinedOutput()
 	if err != nil {
diff --git a/src/cmd/trace/pprof.go b/src/cmd/trace/pprof.go
index 40803ac5f9..47be2a6d1c 100644
--- a/src/cmd/trace/pprof.go
+++ b/src/cmd/trace/pprof.go
@@ -15,10 +15,24 @@ import (
 	"net/http"
 	"os"
 	"os/exec"
+	"path/filepath"
+	"runtime"
 
 	"github.com/google/pprof/profile"
 )
 
+func goCmd() string {
+	var exeSuffix string
+	if runtime.GOOS == "windows" {
+		exeSuffix = ".exe"
+	}
+	path := filepath.Join(runtime.GOROOT(), "bin", "go"+exeSuffix)
+	if _, err := os.Stat(path); err == nil {
+		return path
+	}
+	return "go"
+}
+
 func init() {
 	http.HandleFunc("/io", serveSVGProfile(pprofIO))
 	http.HandleFunc("/block", serveSVGProfile(pprofBlock))
@@ -147,7 +161,7 @@ func serveSVGProfile(prof func(w io.Writer) error) http.HandlerFunc {
 			return
 		}
 		svgFilename := blockf.Name() + ".svg"
-		if output, err := exec.Command("go", "tool", "pprof", "-svg", "-output", svgFilename, blockf.Name()).CombinedOutput(); err != nil {
+		if output, err := exec.Command(goCmd(), "tool", "pprof", "-svg", "-output", svgFilename, blockf.Name()).CombinedOutput(); err != nil {
 			http.Error(w, fmt.Sprintf("failed to execute go tool pprof: %v\n%s", err, output), http.StatusInternalServerError)
 			return
 		}