Inform user how to fix permissions when the observatory URL isn't found on iOS 14 (#65977)

packages/flutter_tools/lib/src/ios/devices.dart

@@ -310,6 +310,7 @@ class IOSDevice extends Device {
     bool prebuiltApplication = false,
     bool ipv6 = false,
     @visibleForTesting Duration fallbackPollingDelay,
+    @visibleForTesting Duration fallbackThrottleTimeout,
     String userIdentifier,
   }) async {
     String packageId;
@@ -402,6 +403,7 @@ class IOSDevice extends Device {
           hostPort: debuggingOptions.hostVmServicePort,
           devicePort: debuggingOptions.deviceVmServicePort,
           ipv6: ipv6,
+          throttleTimeout: fallbackThrottleTimeout ?? const Duration(seconds: 1),
         );
       }
       final int installationResult = await _iosDeploy.runApp(
@@ -441,6 +443,12 @@ class IOSDevice extends Device {
         packageName: FlutterProject.current().manifest.appName,
       );
       if (localUri == null) {
+        if (majorSdkVersion >= 14) {
+          _logger.printError('Failed to attach to the observatory.');
+          _logger.printError(
+              'Try accepting the local network permissions popup, or enable "Settings > Privacy > Local Network" for your app.');
+          _logger.printError('For more information, see https://flutter.dev/docs/development/ios-14#debugging-flutter');
+        }
         return LaunchResult.failed();
       }
       return LaunchResult.succeeded(observatoryUri: localUri);

packages/flutter_tools/lib/src/protocol_discovery.dart

@@ -18,6 +18,7 @@ class ProtocolDiscovery {
     this.serviceName, {
     this.portForwarder,
     this.throttleDuration,
+    this.throttleTimeout,
     this.hostPort,
     this.devicePort,
     this.ipv6,
@@ -34,6 +35,7 @@ class ProtocolDiscovery {
     DeviceLogReader logReader, {
     DevicePortForwarder portForwarder,
     Duration throttleDuration = const Duration(milliseconds: 200),
+    Duration throttleTimeout,
     @required int hostPort,
     @required int devicePort,
     @required bool ipv6,
@@ -44,6 +46,7 @@ class ProtocolDiscovery {
       kObservatoryService,
       portForwarder: portForwarder,
       throttleDuration: throttleDuration,
+      throttleTimeout: throttleTimeout,
       hostPort: hostPort,
       devicePort: devicePort,
       ipv6: ipv6,
@@ -60,6 +63,11 @@ class ProtocolDiscovery {
   /// The time to wait before forwarding a new observatory URIs from [logReader].
   final Duration throttleDuration;
 
+  /// The time between URIs are discovered before timing out when scraping the [logReader].
+  ///
+  /// If null, log scanning will continue indefinitely.
+  final Duration throttleTimeout;
+
   StreamSubscription<String> _deviceLogSubscription;
   _BufferedStreamController<Uri> _uriStreamController;
 
@@ -81,15 +89,21 @@ class ProtocolDiscovery {
   ///
   /// When a new observatory URL: is available in [logReader],
   /// the URLs are forwarded at most once every [throttleDuration].
+  /// Returns when no event has been observed for [throttleTimeout].
   ///
   /// Port forwarding is only attempted when this is invoked,
   /// for each observatory URL in the stream.
   Stream<Uri> get uris {
-    return _uriStreamController.stream
+    Stream<Uri> uriStream = _uriStreamController.stream
       .transform(_throttle<Uri>(
         waitDuration: throttleDuration,
-      ))
-      .asyncMap<Uri>(_forwardPort);
+      ));
+    if (throttleTimeout != null) {
+      // Don't throw a TimeoutException. The URL wasn't found in time, just close the stream.
+      uriStream = uriStream.timeout(throttleTimeout,
+          onTimeout: (EventSink<Uri> sink) => sink.close());
+    }
+    return uriStream.asyncMap<Uri>(_forwardPort);
   }
 
   Future<void> cancel() => _stopScrapingLogs();

packages/flutter_tools/test/general.shard/ios/ios_device_start_prebuilt_test.dart

@@ -266,6 +266,106 @@ void main() {
       Usage: () => MockUsage(),
     });
 
+  group('IOSDevice.startApp on discovery failure local network permissions', () {
+    // Still uses context for analytics and mDNS.
+    testUsingContext('is not prompted on < iOS 14', () async {
+      final FileSystem fileSystem = MemoryFileSystem.test();
+      final FakeProcessManager processManager = FakeProcessManager.list(<FakeCommand>[
+        kDeployCommand,
+        kLaunchDebugCommand,
+      ]);
+     final  BufferLogger logger = BufferLogger.test();
+      final IOSDevice device = setUpIOSDevice(
+        sdkVersion: '13.0',
+        processManager: processManager,
+        fileSystem: fileSystem,
+        logger: logger,
+        vmServiceConnector: (String string, {Log log}) async {
+          throw const io.SocketException(
+            'OS Error: Connection refused, errno = 61, address = localhost, port '
+                '= 58943',
+          );
+        },
+      );
+      final IOSApp iosApp = PrebuiltIOSApp(
+        projectBundleId: 'app',
+        bundleName: 'Runner',
+        bundleDir: fileSystem.currentDirectory,
+      );
+      final FakeDeviceLogReader deviceLogReader = FakeDeviceLogReader();
+
+      device.portForwarder = const NoOpDevicePortForwarder();
+      device.setLogReader(iosApp, deviceLogReader);
+
+      when(MDnsObservatoryDiscovery.instance.getObservatoryUri(any, any, usesIpv6: anyNamed('usesIpv6')))
+          .thenAnswer((Invocation invocation) async => null);
+
+      final LaunchResult launchResult = await device.startApp(iosApp,
+        prebuiltApplication: true,
+        debuggingOptions: DebuggingOptions.enabled(BuildInfo.debug),
+        platformArgs: <String, dynamic>{},
+        fallbackPollingDelay: Duration.zero,
+        fallbackThrottleTimeout: const Duration(milliseconds: 10),
+      );
+
+      expect(launchResult.started, false);
+      expect(launchResult.hasObservatory, false);
+      expect(logger.errorText, isEmpty);
+    }, overrides: <Type, Generator>{
+      MDnsObservatoryDiscovery: () => MockMDnsObservatoryDiscovery(),
+      Usage: () => MockUsage(),
+    });
+
+    // Still uses context for analytics and mDNS.
+    testUsingContext('is prompted on >= iOS 14', () async {
+      final FileSystem fileSystem = MemoryFileSystem.test();
+      final FakeProcessManager processManager = FakeProcessManager.list(<FakeCommand>[
+        kDeployCommand,
+        kLaunchDebugCommand,
+      ]);
+      final BufferLogger logger = BufferLogger.test();
+      final IOSDevice device = setUpIOSDevice(
+        sdkVersion: '14.0',
+        processManager: processManager,
+        fileSystem: fileSystem,
+        logger: logger,
+        vmServiceConnector: (String string, {Log log}) async {
+          throw const io.SocketException(
+            'OS Error: Connection refused, errno = 61, address = localhost, port '
+                '= 58943',
+          );
+        },
+      );
+      final IOSApp iosApp = PrebuiltIOSApp(
+        projectBundleId: 'app',
+        bundleName: 'Runner',
+        bundleDir: fileSystem.currentDirectory,
+      );
+      final FakeDeviceLogReader deviceLogReader = FakeDeviceLogReader();
+
+      device.portForwarder = const NoOpDevicePortForwarder();
+      device.setLogReader(iosApp, deviceLogReader);
+
+      when(MDnsObservatoryDiscovery.instance.getObservatoryUri(any, any, usesIpv6: anyNamed('usesIpv6')))
+          .thenAnswer((Invocation invocation) async => null);
+
+      final LaunchResult launchResult = await device.startApp(iosApp,
+        prebuiltApplication: true,
+        debuggingOptions: DebuggingOptions.enabled(BuildInfo.debug),
+        platformArgs: <String, dynamic>{},
+        fallbackPollingDelay: Duration.zero,
+        fallbackThrottleTimeout: const Duration(milliseconds: 10),
+      );
+
+      expect(launchResult.started, false);
+      expect(launchResult.hasObservatory, false);
+      expect(logger.errorText, contains('Settings > Privacy > Local Network'));
+    }, overrides: <Type, Generator>{
+      MDnsObservatoryDiscovery: () => MockMDnsObservatoryDiscovery(),
+      Usage: () => MockUsage(),
+    });
+  });
+
   // Still uses context for TimeoutConfiguration and usage
   testUsingContext('IOSDevice.startApp succeeds in release mode', () async {
     final FileSystem fileSystem = MemoryFileSystem.test();
@@ -430,7 +530,7 @@ IOSDevice setUpIOSDevice({
     fileSystem: fileSystem ?? MemoryFileSystem.test(),
     platform: macPlatform,
     iProxy: IProxy.test(logger: logger, processManager: processManager ?? FakeProcessManager.any()),
-    logger: BufferLogger.test(),
+    logger: logger ?? BufferLogger.test(),
     iosDeploy: IOSDeploy(
       logger: logger ?? BufferLogger.test(),
       platform: macPlatform,