Allow --ipv6 flag for flutter attach on iOS devices (#123822)

Allow --ipv6 flag for flutter attach on iOS devices

packages/flutter_tools/lib/src/commands/attach.dart

@@ -219,11 +219,19 @@ known, it can be explicitly provided to attach via the command-line, e.g.
     MacOSDesignedForIPadDevices.allowDiscovery = true;
 
     await super.validateCommand();
-    if (await findTargetDevice() == null) {
+
+    final Device? targetDevice = await findTargetDevice();
+    if (targetDevice == null) {
       throwToolExit(null);
     }
+
     debugPort;
-    if (debugPort == null && debugUri == null && argResults!.wasParsed(FlutterCommand.ipv6Flag)) {
+    // Allow --ipv6 for iOS devices even if --debug-port and --debug-url
+    // are unknown
+    if (!_isIOSDevice(targetDevice) &&
+        debugPort == null &&
+        debugUri == null &&
+        argResults!.wasParsed(FlutterCommand.ipv6Flag)) {
       throwToolExit(
         'When the --debug-port or --debug-url is unknown, this command determines '
         'the value of --ipv6 on its own.',
@@ -311,7 +319,7 @@ known, it can be explicitly provided to attach via the command-line, e.g.
           }
           rethrow;
         }
-      } else if ((device is IOSDevice) || (device is IOSSimulator) || (device is MacOSDesignedForIPadDevice)) {
+      } else if (_isIOSDevice(device)) {
         // Protocol Discovery relies on logging. On iOS earlier than 13, logging is gathered using syslog.
         // syslog is not available for iOS 13+. For iOS 13+, Protocol Discovery gathers logs from the VMService.
         // Since we don't have access to the VMService yet, Protocol Discovery cannot be used for iOS 13+.
@@ -395,8 +403,6 @@ known, it can be explicitly provided to attach via the command-line, e.g.
           );
         _logger.printStatus('Waiting for a connection from Flutter on ${device.name}...');
         vmServiceUri = vmServiceDiscovery.uris;
-        // Determine ipv6 status from the scanned logs.
-        usesIpv6 = vmServiceDiscovery.ipv6;
       }
     } else {
       vmServiceUri = Stream<Uri>
@@ -544,6 +550,12 @@ known, it can be explicitly provided to attach via the command-line, e.g.
   }
 
   Future<void> _validateArguments() async { }
+
+  bool _isIOSDevice(Device device) {
+    return (device is IOSDevice) ||
+        (device is IOSSimulator) ||
+        (device is MacOSDesignedForIPadDevice);
+  }
 }
 
 class HotRunnerFactory {

packages/flutter_tools/lib/src/protocol_discovery.dart

@@ -20,9 +20,10 @@ class ProtocolDiscovery {
     required this.throttleDuration,
     this.hostPort,
     this.devicePort,
-    required this.ipv6,
+    required bool ipv6,
     required Logger logger,
-  }) : _logger = logger {
+  }) : _logger = logger,
+       _ipv6 = ipv6 {
     _deviceLogSubscription = logReader.logLines.listen(
       _handleLine,
       onDone: _stopScrapingLogs,
@@ -56,7 +57,7 @@ class ProtocolDiscovery {
   final DevicePortForwarder? portForwarder;
   final int? hostPort;
   final int? devicePort;
-  final bool ipv6;
+  final bool _ipv6;
   final Logger _logger;
 
   /// The time to wait before forwarding a new VM Service URIs from [logReader].
@@ -144,7 +145,7 @@ class ProtocolDiscovery {
       hostUri = deviceUri.replace(port: actualHostPort);
     }
 
-    if (InternetAddress(hostUri.host).isLoopback && ipv6) {
+    if (InternetAddress(hostUri.host).isLoopback && _ipv6) {
       hostUri = hostUri.replace(host: InternetAddress.loopbackIPv6.host);
     }
     return hostUri;

packages/flutter_tools/lib/src/runner/flutter_command.dart

@@ -603,8 +603,7 @@ abstract class FlutterCommand extends Command<void> {
     argParser.addFlag(ipv6Flag,
       negatable: false,
       help: 'Binds to IPv6 localhost instead of IPv4 when the flutter tool '
-            'forwards the host port to a device port. Not used when the '
-            '"--debug-port" flag is not set.',
+            'forwards the host port to a device port.',
       hide: !verboseHelp,
     );
     _usesIpv6Flag = true;

packages/flutter_tools/test/commands.shard/hermetic/attach_test.dart

@@ -591,7 +591,7 @@ void main() {
         DeviceManager: () => testDeviceManager,
       });
 
-      testUsingContext('exits when ipv6 is specified and debug-port is not', () async {
+      testUsingContext('exits when ipv6 is specified and debug-port is not on non-iOS device', () async {
         testDeviceManager.devices = <Device>[device];
 
         final AttachCommand command = AttachCommand(
@@ -615,7 +615,63 @@ void main() {
         FileSystem: () => testFileSystem,
         ProcessManager: () => FakeProcessManager.any(),
         DeviceManager: () => testDeviceManager,
-      },);
+      });
+
+      testUsingContext('succeeds when ipv6 is specified and debug-port is not on iOS device', () async {
+        final FakeIOSDevice device = FakeIOSDevice(
+          logReader: fakeLogReader,
+          portForwarder: portForwarder,
+          majorSdkVersion: 12,
+          onGetLogReader: () {
+            fakeLogReader.addLine('Foo');
+            fakeLogReader.addLine('The Dart VM service is listening on http://[::1]:$devicePort');
+            return fakeLogReader;
+          },
+        );
+        testDeviceManager.devices = <Device>[device];
+        final Completer<void> completer = Completer<void>();
+        final StreamSubscription<String> loggerSubscription = logger.stream.listen((String message) {
+          if (message == '[verbose] VM Service URL on device: http://[::1]:$devicePort') {
+            // The "VM Service URL on device" message is output by the ProtocolDiscovery when it found the VM Service.
+            completer.complete();
+          }
+        });
+        final FakeHotRunner hotRunner = FakeHotRunner();
+        hotRunner.onAttach = (
+          Completer<DebugConnectionInfo>? connectionInfoCompleter,
+          Completer<void>? appStartedCompleter,
+          bool allowExistingDdsInstance,
+          bool enableDevTools,
+        ) async => 0;
+        hotRunner.exited = false;
+        hotRunner.isWaitingForVmService = false;
+        final FakeHotRunnerFactory hotRunnerFactory = FakeHotRunnerFactory()
+          ..hotRunner = hotRunner;
+
+        await createTestCommandRunner(AttachCommand(
+          hotRunnerFactory: hotRunnerFactory,
+          artifacts: artifacts,
+          stdio: stdio,
+          logger: logger,
+          terminal: terminal,
+          signals: signals,
+          platform: platform,
+          processInfo: processInfo,
+          fileSystem: testFileSystem,
+        )).run(<String>['attach', '--ipv6']);
+        await completer.future;
+
+        expect(portForwarder.devicePort, devicePort);
+        expect(portForwarder.hostPort, hostPort);
+
+        await fakeLogReader.dispose();
+        await loggerSubscription.cancel();
+      }, overrides: <Type, Generator>{
+        FileSystem: () => testFileSystem,
+        ProcessManager: () => FakeProcessManager.any(),
+        Logger: () => logger,
+        DeviceManager: () => testDeviceManager,
+      });
 
       testUsingContext('exits when vm-service-port is specified and debug-port is not', () async {
         device.onGetLogReader = () {