Add a flag to prevent launching twice. (#910)

* Add a flag to prevent launching twice.

* fix go version bug

lib/launcher/error.go

@@ -0,0 +1,6 @@
+package launcher
+
+import "errors"
+
+// ErrAlreadyLaunched is an error that indicates the launcher has already been launched.
+var ErrAlreadyLaunched = errors.New("already launched")

lib/launcher/launcher.go

@@ -13,6 +13,7 @@ import (
  "path/filepath"
  "sort"
  "strings"
+ "sync/atomic"
 
  "github.com/go-rod/rod/lib/defaults"
  "github.com/go-rod/rod/lib/launcher/flags"
@@ -39,6 +40,8 @@ type Launcher struct {
 
  managed bool
  serviceURL string
+
+ isLaunched int32 // zero means not launched
 }
 
 // New returns the default arguments to start browser.
@@ -377,7 +380,13 @@ func (l *Launcher) MustLaunch() string {
 // Launch a standalone temp browser instance and returns the debug url.
 // bin and profileDir are optional, set them to empty to use the default values.
 // If you want to reuse sessions, such as cookies, set the [Launcher.UserDataDir] to the same location.
+//
+// Please note launcher can only be used once.
 func (l *Launcher) Launch() (string, error) {
+ if l.hasLaunched() {
+ return "", ErrAlreadyLaunched
+ }
+
  defer l.ctxCancel()
 
  bin, err := l.getBin()
@@ -430,6 +439,10 @@ func (l *Launcher) Launch() (string, error) {
  return ResolveURL(u)
 }
 
+func (l *Launcher) hasLaunched() bool {
+ return !atomic.CompareAndSwapInt32(&l.isLaunched, 0, 1)
+}
+
 func (l *Launcher) setupCmd(cmd *exec.Cmd) {
  l.osSetupCmd(cmd)
 

lib/launcher/launcher_test.go

@@ -310,3 +310,17 @@ func TestBrowserDownloadErr(t *testing.T) {
  }}
  g.Err(b.Download())
 }
+
+func TestLaunchMultiTimes(t *testing.T) {
+ g := setup(t)
+
+ // first time launch, success.
+ l := launcher.New()
+ u, e := l.Launch()
+ g.Neq(u, "")
+ g.E(e)
+
+ // second time launch, failed with ErrAlreadyLaunched.
+ _, e = l.Launch()
+ g.Eq(e, launcher.ErrAlreadyLaunched)
+}