fix: shouldn't reset the user preferences by default

Resolve #1041

lib/launcher/launcher.go

@@ -68,8 +68,6 @@ func New() *Launcher {
 		// enable headless by default
 		flags.Headless: nil,
 
-		flags.Preferences: {`{"plugins":{"always_open_pdf_externally": true}}`},
-
 		// to disable the init blank window
 		"no-first-run":      nil,
 		"no-startup-window": nil,
@@ -255,6 +253,12 @@ func (l *Launcher) Preferences(pref string) *Launcher {
 	return l.Set(flags.Preferences, pref)
 }
 
+// AlwaysOpenPDFExternally switch.
+// It will set chromium user preferences to enable the always_open_pdf_externally option.
+func (l *Launcher) AlwaysOpenPDFExternally() *Launcher {
+	return l.Set(flags.Preferences, `{"plugins":{"always_open_pdf_externally": true}}`)
+}
+
 // Leakless switch. If enabled, the browser will be force killed after the Go process exits.
 // The doc of leakless: https://github.com/ysmood/leakless.
 func (l *Launcher) Leakless(enable bool) *Launcher {

lib/launcher/launcher_test.go

@@ -65,7 +65,7 @@ func TestLaunch(t *testing.T) {
 	defaults.Proxy = "test.com"
 	defer func() { defaults.ResetWith("") }()
 
-	l := launcher.New().Preferences("")
+	l := launcher.New().Preferences("").AlwaysOpenPDFExternally()
 	defer l.Kill()
 
 	u := l.MustLaunch()