Make flutter attach respect the --dds-port flag. (#105560)

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

@@ -428,6 +428,7 @@ known, it can be explicitly provided to attach via the command-line, e.g.
     final DebuggingOptions debuggingOptions = DebuggingOptions.enabled(
       buildInfo,
       enableDds: enableDds,
+      ddsPort: ddsPort,
       devToolsServerAddress: devToolsServerAddress,
     );
 

packages/flutter_tools/test/integration.shard/flutter_attach_test.dart

@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 import 'package:file/file.dart';
+import 'package:flutter_tools/src/base/io.dart';
 import 'package:vm_service/vm_service.dart';
 
 import '../src/common.dart';
@@ -10,14 +11,30 @@ import 'test_data/basic_project.dart';
 import 'test_driver.dart';
 import 'test_utils.dart';
 
+Future<int> getFreePort() async {
+  int port = 0;
+  final ServerSocket serverSocket = await ServerSocket.bind(InternetAddress.loopbackIPv4, 0);
+  port = serverSocket.port;
+  await serverSocket.close();
+  return port;
+}
+
 void main() {
-  late FlutterRunTestDriver flutterRun, flutterAttach;
   final BasicProject project = BasicProject();
   late Directory tempDir;
 
   setUp(() async {
     tempDir = createResolvedTempDirectorySync('attach_test.');
     await project.setUpIn(tempDir);
+  });
+
+  tearDown(() {
+    tryToDelete(tempDir);
+  });
+
+  group('DDS in flutter run', () {
+    late FlutterRunTestDriver flutterRun, flutterAttach;
+    setUp(() {
       flutterRun = FlutterRunTestDriver(tempDir,    logPrefix: '   RUN  ');
       flutterAttach = FlutterRunTestDriver(
         tempDir,
@@ -32,7 +49,6 @@ void main() {
     tearDown(() async {
       await flutterAttach.detach();
       await flutterRun.stop();
-    tryToDelete(tempDir);
     });
 
     testWithoutContext('can hot reload', () async {
@@ -103,4 +119,42 @@ void main() {
         matches: equals(vmServiceUri),
       );
     });
+  });
+
+  group('DDS in flutter attach', () {
+    late FlutterRunTestDriver flutterRun, flutterAttach;
+    setUp(() {
+      flutterRun = FlutterRunTestDriver(
+        tempDir,
+        logPrefix: '   RUN  ',
+        spawnDdsInstance: false,
+      );
+      flutterAttach = FlutterRunTestDriver(
+        tempDir,
+        logPrefix: 'ATTACH  ',
+      );
+    });
+
+    tearDown(() async {
+      await flutterAttach.detach();
+      await flutterRun.stop();
+    });
+
+    testWithoutContext('uses the designated dds port', () async {
+      final int ddsPort = await getFreePort();
+
+      await flutterRun.run(withDebugger: true);
+      await flutterAttach.attach(
+        flutterRun.vmServicePort!,
+        additionalCommandArgs: <String>[
+          '--dds-port=$ddsPort',
+        ],
+      );
+
+      final Response response = await flutterAttach.callServiceExtension('ext.flutter.connectedVmServiceUri');
+      final String vmServiceUriString = response.json!['value'] as String;
+      final Uri vmServiceUri = Uri.parse(vmServiceUriString);
+      expect(vmServiceUri.port, equals(ddsPort));
+    });
+  });
 }