cmd: add internal/browser package

cmd/cover, cmd/trace, and cmd/pprof all open browsers.
'go bug' will soon also open a browser.
It is time to unify the browser-handling code.

Change-Id: Iee6b443e21e938aeaaac366a1aefb1afbc7d9b2c
Reviewed-on: https://go-review.googlesource.com/29160
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/cmd/cover/html.go

@@ -7,15 +7,14 @@ package main
 import (
 	"bufio"
 	"bytes"
+	"cmd/internal/browser"
 	"fmt"
 	"html/template"
 	"io"
 	"io/ioutil"
 	"math"
 	"os"
-	"os/exec"
 	"path/filepath"
-	"runtime"
 )
 
 // htmlOutput reads the profile data from profile and generates an HTML
@@ -74,7 +73,7 @@ func htmlOutput(profile, outfile string) error {
 	}
 
 	if outfile == "" {
-		if !startBrowser("file://" + out.Name()) {
+		if !browser.Open("file://" + out.Name()) {
 			fmt.Fprintf(os.Stderr, "HTML output written to %s\n", out.Name())
 		}
 	}
@@ -133,23 +132,6 @@ func htmlGen(w io.Writer, src []byte, boundaries []Boundary) error {
 	return dst.Flush()
 }
 
-// startBrowser tries to open the URL in a browser
-// and reports whether it succeeds.
-func startBrowser(url string) bool {
-	// try to start the browser
-	var args []string
-	switch runtime.GOOS {
-	case "darwin":
-		args = []string{"open"}
-	case "windows":
-		args = []string{"cmd", "/c", "start"}
-	default:
-		args = []string{"xdg-open"}
-	}
-	cmd := exec.Command(args[0], append(args[1:], url)...)
-	return cmd.Start() == nil
-}
-
 // rgb returns an rgb value for the specified coverage value
 // between 0 (no coverage) and 10 (max coverage).
 func rgb(n int) string {

src/cmd/internal/browser/browser.go

@@ -0,0 +1,41 @@
+// 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.
+
+// Package browser provides utilities for interacting with users' browsers.
+package browser
+
+import (
+	"os"
+	"os/exec"
+	"runtime"
+)
+
+// Commands returns a list of possible commands to use to open a url.
+func Commands() [][]string {
+	var cmds [][]string
+	if exe := os.Getenv("BROWSER"); exe != "" {
+		cmds = append(cmds, []string{exe})
+	}
+	switch runtime.GOOS {
+	case "darwin":
+		cmds = append(cmds, []string{"/usr/bin/open"})
+	case "windows":
+		cmds = append(cmds, []string{"cmd", "/c", "start"})
+	default:
+		cmds = append(cmds, []string{"xdg-open"})
+	}
+	cmds = append(cmds, []string{"chrome"}, []string{"google-chrome"}, []string{"firefox"})
+	return cmds
+}
+
+// Open tries to open url in a browser and reports whether it succeeded.
+func Open(url string) bool {
+	for _, args := range Commands() {
+		cmd := exec.Command(args[0], append(args[1:], url)...)
+		if cmd.Start() == nil {
+			return true
+		}
+	}
+	return false
+}

src/cmd/internal/pprof/commands/commands.go

@@ -12,10 +12,10 @@ import (
 	"io/ioutil"
 	"os"
 	"os/exec"
-	"runtime"
 	"strings"
 	"time"
 
+	"cmd/internal/browser"
 	"cmd/internal/pprof/plugin"
 	"cmd/internal/pprof/report"
 	"cmd/internal/pprof/svg"
@@ -85,18 +85,9 @@ func PProf(c Completer, interactive **bool) Commands {
 // on the current platform
 func browsers() []string {
 	var cmds []string
-	if exe := os.Getenv("BROWSER"); exe != "" {
-		cmds = append(cmds, exe)
+	for _, cmd := range browser.Commands() {
+		cmds = append(cmds, strings.Join(cmd, " "))
 	}
-	switch runtime.GOOS {
-	case "darwin":
-		cmds = append(cmds, "/usr/bin/open")
-	case "windows":
-		cmds = append(cmds, "cmd /c start")
-	default:
-		cmds = append(cmds, "xdg-open")
-	}
-	cmds = append(cmds, "chrome", "google-chrome", "firefox")
 	return cmds
 }
 

src/cmd/trace/main.go

@@ -20,6 +20,7 @@ package main
 
 import (
 	"bufio"
+	"cmd/internal/browser"
 	"flag"
 	"fmt"
 	"html/template"
@@ -28,8 +29,6 @@ import (
 	"net"
 	"net/http"
 	"os"
-	"os/exec"
-	"runtime"
 	"sync"
 )
 
@@ -96,7 +95,7 @@ func main() {
 	ranges = splitTrace(data)
 
 	log.Printf("Opening browser")
-	if !startBrowser("http://" + ln.Addr().String()) {
+	if !browser.Open("http://" + ln.Addr().String()) {
 		fmt.Fprintf(os.Stderr, "Trace viewer is listening on http://%s\n", ln.Addr().String())
 	}
 
@@ -162,24 +161,6 @@ var templMain = template.Must(template.New("").Parse(`
 </html>
 `))
 
-// startBrowser tries to open the URL in a browser
-// and reports whether it succeeds.
-// Note: copied from x/tools/cmd/cover/html.go
-func startBrowser(url string) bool {
-	// try to start the browser
-	var args []string
-	switch runtime.GOOS {
-	case "darwin":
-		args = []string{"open"}
-	case "windows":
-		args = []string{"cmd", "/c", "start"}
-	default:
-		args = []string{"xdg-open"}
-	}
-	cmd := exec.Command(args[0], append(args[1:], url)...)
-	return cmd.Start() == nil
-}
-
 func dief(msg string, args ...interface{}) {
 	fmt.Fprintf(os.Stderr, msg, args...)
 	os.Exit(1)