Update `flutter start` for iOS simulator

packages/flutter_tools/lib/src/device.dart

@@ -187,20 +187,12 @@ class IOSDevice extends Device {
     return false;
   }
 
-  Future<bool> buildPrecompiledApplication(ApplicationPackage app) async {
-    int result = await runCommandAndStreamOutput([
-      '/usr/bin/env', 'xcrun', 'xcodebuild', '-target', 'Runner', '-configuration', 'Release'
-    ], workingDirectory: app.localPath);
-
-    return result == 0;
-  }
-
   @override
   Future<bool> startApp(ApplicationPackage app) async {
     logging.fine("Attempting to build and install ${app.name} on $id");
 
     // Step 1: Install the precompiled application if necessary
-    bool buildResult = await buildPrecompiledApplication(app);
+    bool buildResult = await _buildIOSXcodeProject(app, true);
 
     if (!buildResult) {
       logging.severe('Could not build the precompiled application for the device');
@@ -257,11 +249,6 @@ class IOSDevice extends Device {
       ]);
       return true;
     } else {
-      // TODO(iansf): It may be possible to make this work on Linux. Since this
-      //              functionality appears to be the only that prevents us from
-      //              supporting iOS on Linux, it may be worth putting some time
-      //              into investigating this.
-      //              See https://bbs.archlinux.org/viewtopic.php?id=192655
       return false;
     }
     return false;
@@ -364,8 +351,6 @@ class IOSSimulator extends Device {
     List<IOSSimulator> devices = [];
     String id = _getRunningSimulatorID(mockIOS);
     if (id != null) {
-      // TODO(iansf): get the simulator's name
-      // String name = _getDeviceName(id, mockIOS);
       devices.add(new IOSSimulator(id: id));
     }
     return devices;
@@ -448,20 +433,53 @@ class IOSSimulator extends Device {
 
   @override
   Future<bool> startApp(ApplicationPackage app) async {
-    if (!isAppInstalled(app)) {
+    logging.fine('Building ${app.name} for ${id}');
+
+    // Step 1: Build the Xcode project
+    bool buildResult = await _buildIOSXcodeProject(app, false);
+    if (!buildResult) {
+      logging.severe('Could not build the application for the simulator');
       return false;
     }
-    try {
-      if (id == defaultDeviceID) {
-        runCheckedSync(
-            [xcrunPath, 'simctl', 'launch', 'booted', app.id]);
-      } else {
-        runCheckedSync([xcrunPath, 'simctl', 'launch', id, app.id]);
+
+    // Step 2: Assert that the Xcode project was successfully built
+    Directory bundle = new Directory(path.join(app.localPath, 'build', 'Release-iphonesimulator', 'Runner.app'));
+    bool bundleExists = await bundle.exists();
+    if (!bundleExists) {
+      logging.severe('Could not find the built application bundle at ${bundle.path}');
+      return false;
     }
-      return true;
-    } catch (e) {
+
+    // Step 3: Install the updated bundle to the simulator
+    int installResult = await runCommandAndStreamOutput([
+      xcrunPath,
+      'simctl',
+      'install',
+      id == defaultDeviceID ? 'booted' : id,
+      path.absolute(bundle.path)
+    ]);
+
+    if (installResult != 0) {
+      logging.severe('Could not install the application bundle on the simulator');
       return false;
     }
+
+    // Step 4: Launch the updated application in the simulator
+    int launchResult = await runCommandAndStreamOutput([
+      xcrunPath,
+      'simctl',
+      'launch',
+      id == defaultDeviceID ? 'booted' : id,
+      app.id
+    ]);
+
+    if (launchResult != 0) {
+      logging.severe('Could not launch the freshly installed application on the simulator');
+      return false;
+    }
+
+    logging.fine('Successfully started ${app.name} on $id');
+    return true;
   }
 
   @override
@@ -1038,7 +1056,11 @@ class DeviceStore {
           break;
         case TargetPlatform.iOSSimulator:
           assert(iOSSimulator == null);
+          iOSSimulator = _deviceForConfig(config, IOSSimulator.getAttachedDevices());
+          if (iOSSimulator == null) {
+            // Creates a simulator with the default identifier
             iOSSimulator = new IOSSimulator();
+          }
           break;
         case TargetPlatform.mac:
         case TargetPlatform.linux:
@@ -1049,3 +1071,17 @@ class DeviceStore {
     return new DeviceStore(android: android, iOS: iOS, iOSSimulator: iOSSimulator);
   }
 }
+
+Future<bool> _buildIOSXcodeProject(ApplicationPackage app, bool isDevice) async {
+  List<String> command = [
+    '/usr/bin/env', 'xcrun', 'xcodebuild', '-target', 'Runner', '-configuration', 'Release'
+  ];
+
+  if (!isDevice) {
+    command.addAll(['-sdk', 'iphonesimulator']);
+  }
+
+  int result = await runCommandAndStreamOutput(command,
+      workingDirectory: app.localPath);
+  return result == 0;
+}