Replace applescript with https://github.com/sindresorhus/opn

This allows opening the Chrome debugger on OS X, Linux, and Windows.

`isDebuggerConnected()` addresses the problem in facebook#510 where the dev tools
would only open once per server session.

package.json

@@ -65,6 +65,7 @@
     "joi": "^6.6.1",
     "jstransform": "^11.0.3",
     "module-deps": "^3.9.1",
+    "opn": "^3.0.2",
     "optimist": "^0.6.1",
     "progress": "^1.1.8",
     "promise": "^7.0.4",

packager/getDevToolsMiddleware.js

@@ -11,8 +11,20 @@
 var execFile = require('child_process').execFile;
 var fs = require('fs');
 var path = require('path');
+var opn = require('opn');
 
-module.exports = function(options) {
+function getChromeAppName() {
+  switch (process.platform) {
+  case 'darwin':
+    return 'google chrome';
+  case 'win32':
+    return 'chrome';
+  default:
+    return 'google-chrome';
+  }
+}
+
+module.exports = function(options, isDebuggerConnected) {
   return function(req, res, next) {
     if (req.url === '/debugger-ui') {
       var debuggerPath = path.join(__dirname, 'debugger.html');
@@ -29,20 +41,19 @@ module.exports = function(options) {
         'If you still need this, please let us know.'
       );
     } else if (req.url === '/launch-chrome-devtools') {
+      if (isDebuggerConnected()) {
+        // Dev tools are already open; no need to open another session
+        res.end('OK');
+        return;
+      }
       var debuggerURL = 'http://localhost:' + options.port + '/debugger-ui';
-      var script = 'launchChromeDevTools.applescript';
       console.log('Launching Dev Tools...');
-      execFile(
-        path.join(__dirname, script), [debuggerURL],
-        function(err, stdout, stderr) {
-          if (err) {
-            console.log('Failed to run ' + script, err);
-          }
-          console.log(stdout);
-          console.warn(stderr);
+      opn(debuggerURL, {app: [getChromeAppName()]}, function(err) {
+        if (err) {
+          console.error('Google Chrome exited with error:', err);
+          next(err)
         }
-      );
-      res.end('OK');
+      });
     } else {
       next();
     }

packager/packager.js

@@ -160,7 +160,13 @@ var server = runServer(options, function() {
   console.log('\nReact packager ready.\n');
 });
 
-webSocketProxy.attachToServer(server, '/debugger-proxy');
+var proxy = webSocketProxy.attachToServer(server, '/debugger-proxy');
+
+function isDebuggerConnected() {
+  // Debugger is connected if the app and at least one browser are connected
+  // to the websocket proxy.
+  return proxy.clientsCount() >= 2;
+}
 
 function getAppMiddleware(options) {
   var transformerPath = options.transformer;
@@ -191,7 +197,7 @@ function runServer(
 ) {
   var app = connect()
     .use(loadRawBodyMiddleware)
-    .use(getDevToolsMiddleware(options))
+    .use(getDevToolsMiddleware(options, isDebuggerConnected))
     .use(openStackFrameInEditorMiddleware)
     .use(statusPageMiddleware)
     .use(systraceProfileMiddleware)

packager/webSocketProxy.js

@@ -57,7 +57,12 @@ function attachToServer(server, path) {
     });
   });
 
-  return wss;
+  return {
+    server: wss,
+    clientsCount: function() {
+      return clients.length;
+    }
+  };
 }
 
 module.exports = {