[dap] Don't wait for appStarted before responding to launch/attach + don't...

[dap] Don't wait for appStarted before responding to launch/attach + don't call app.stop for unstarted app (#109386)

packages/flutter_tools/lib/src/debug_adapters/flutter_adapter.dart

@@ -59,11 +59,9 @@ class FlutterDebugAdapter extends DartDebugAdapter<FlutterLaunchRequestArguments
   /// Whether or not the app.started event has been received.
   bool get _receivedAppStarted => appStartedCompleter.isCompleted;
 
-  /// The VM Service URI received from the app.debugPort event.
-  Uri? _vmServiceUri;
-
   /// The appId of the current running Flutter app.
-  String? _appId;
+  @visibleForTesting
+  String? appId;
 
   /// The ID to use for the next request sent to the Flutter run daemon.
   int _flutterRequestId = 1;
@@ -311,13 +309,6 @@ class FlutterDebugAdapter extends DartDebugAdapter<FlutterLaunchRequestArguments
       processArgs: processArgs,
       env: args.env,
     );
-
-    // Delay responding until the app is launched and (optionally) the debugger
-    // is connected.
-    await appStartedCompleter.future;
-    if (enableDebugger) {
-      await debuggerInitialized;
-    }
   }
 
   @visibleForOverriding
@@ -404,23 +395,22 @@ class FlutterDebugAdapter extends DartDebugAdapter<FlutterLaunchRequestArguments
     // Send a request to stop/detach to give Flutter chance to do some cleanup.
     // It's possible the Flutter process will terminate before we process the
     // response, so accept either a response or the process exiting.
-    final String method = isAttach ? 'app.detach' : 'app.stop';
-    await Future.any<void>(<Future<void>>[
-      sendFlutterRequest(method, <String, Object?>{'appId': _appId}),
-      _process?.exitCode ?? Future<void>.value(),
-    ]);
+    if (appId != null) {
+      final String method = isAttach ? 'app.detach' : 'app.stop';
+      await Future.any<void>(<Future<void>>[
+        sendFlutterRequest(method, <String, Object?>{'appId': appId}),
+        _process?.exitCode ?? Future<void>.value(),
+      ]);
+    }
 
     terminatePids(ProcessSignal.sigterm);
     await _process?.exitCode;
   }
 
   /// Connects to the VM Service if the app.started event has fired, and a VM Service URI is available.
-  void _connectDebuggerIfReady() {
-    final Uri? serviceUri = _vmServiceUri;
-
-    if (_receivedAppStarted && serviceUri != null) {
+  Future<void> _connectDebugger(Uri vmServiceUri) async {
       if (enableDebugger) {
-        connectDebugger(serviceUri);
+        await connectDebugger(vmServiceUri);
       } else {
         // Usually, `connectDebugger` (in the base Dart adapter) will send this
         // event when it connects a debugger. Since we're not connecting a
@@ -431,29 +421,30 @@ class FlutterDebugAdapter extends DartDebugAdapter<FlutterLaunchRequestArguments
         //   adapter once rolled into Flutter.
         sendEvent(
           RawEventBody(<String, Object?>{
-            'vmServiceUri': serviceUri.toString(),
+            'vmServiceUri': vmServiceUri.toString(),
           }),
           eventType: 'dart.debuggerUris',
         );
       }
-    }
   }
 
   /// Handles the app.start event from Flutter.
   void _handleAppStart(Map<String, Object?> params) {
-    _appId = params['appId'] as String?;
-    assert(_appId != null);
+    appId = params['appId'] as String?;
+    if(appId == null) {
+      throw DebugAdapterException('Unexpected null `appId` in app.start event');
+    }
   }
 
   /// Handles the app.started event from Flutter.
-  void _handleAppStarted() {
+  Future<void> _handleAppStarted() async {
     appStartedCompleter.complete();
-    _connectDebuggerIfReady();
 
     // Send a custom event so the editor knows the app has started.
     //
     // This may be useful when there's no VM Service (for example Profile mode)
     // but the editor still wants to know that startup has finished.
+    await debuggerInitialized; // Ensure we're fully initialized before sending.
     sendEvent(
       RawEventBody(<String, Object?>{}),
       eventType: 'flutter.appStarted',
@@ -472,13 +463,16 @@ class FlutterDebugAdapter extends DartDebugAdapter<FlutterLaunchRequestArguments
   }
 
   /// Handles the app.debugPort event from Flutter, connecting to the VM Service if everything else is ready.
-  void _handleDebugPort(Map<String, Object?> params) {
+  Future<void> _handleDebugPort(Map<String, Object?> params) async {
     // Capture the VM Service URL which we'll connect to when we get app.started.
     final String? wsUri = params['wsUri'] as String?;
     if (wsUri != null) {
-      _vmServiceUri = Uri.parse(wsUri);
+      final Uri vmServiceUri = Uri.parse(wsUri);
+      // Also wait for app.started before we connect, to ensure Flutter's
+      // initialization is all complete.
+      await appStartedCompleter.future;
+      await _connectDebugger(vmServiceUri);
     }
-    _connectDebuggerIfReady();
   }
 
   /// Handles the Flutter process exiting, terminating the debug session if it has not already begun terminating.
@@ -601,7 +595,7 @@ class FlutterDebugAdapter extends DartDebugAdapter<FlutterLaunchRequestArguments
   ]) async {
     try {
       await sendFlutterRequest('app.restart', <String, Object?>{
-        'appId': _appId,
+        'appId': appId,
         'fullRestart': fullRestart,
         'pause': enableDebugger,
         'reason': reason,

packages/flutter_tools/test/general.shard/dap/flutter_adapter_test.dart

@@ -120,6 +120,30 @@ void main() {
 
         expect(adapter.flutterRequests, contains('app.stop'));
       });
+
+      test('does not call "app.stop" on terminateRequest if app was not started', () async {
+        final MockFlutterDebugAdapter adapter = MockFlutterDebugAdapter(
+          fileSystem: MemoryFileSystem.test(style: fsStyle),
+          platform: platform,
+          simulateAppStarted: false,
+        );
+
+        final FlutterLaunchRequestArguments args = FlutterLaunchRequestArguments(
+          cwd: '/project',
+          program: 'foo.dart',
+        );
+
+        await adapter.configurationDoneRequest(MockRequest(), null, () {});
+        final Completer<void> launchCompleter = Completer<void>();
+        await adapter.launchRequest(MockRequest(), args, launchCompleter.complete);
+        await launchCompleter.future;
+
+        final Completer<void> terminateCompleter = Completer<void>();
+        await adapter.terminateRequest(MockRequest(), TerminateArguments(restart: false), terminateCompleter.complete);
+        await terminateCompleter.future;
+
+        expect(adapter.flutterRequests, isNot(contains('app.stop')));
+      });
     });
 
     group('attachRequest', () {

packages/flutter_tools/test/general.shard/dap/mocks.dart

@@ -15,6 +15,7 @@ class MockFlutterDebugAdapter extends FlutterDebugAdapter {
   factory MockFlutterDebugAdapter({
     required FileSystem fileSystem,
     required Platform platform,
+    bool simulateAppStarted = true,
   }) {
     final StreamController<List<int>> stdinController = StreamController<List<int>>();
     final StreamController<List<int>> stdoutController = StreamController<List<int>>();
@@ -26,6 +27,7 @@ class MockFlutterDebugAdapter extends FlutterDebugAdapter {
       channel,
       fileSystem: fileSystem,
       platform: platform,
+      simulateAppStarted: simulateAppStarted,
     );
   }
 
@@ -35,10 +37,12 @@ class MockFlutterDebugAdapter extends FlutterDebugAdapter {
     ByteStreamServerChannel channel, {
     required FileSystem fileSystem,
     required Platform platform,
+    this.simulateAppStarted = true,
   }) : super(channel, fileSystem: fileSystem, platform: platform);
 
   final StreamSink<List<int>> stdin;
   final Stream<List<int>> stdout;
+  final bool simulateAppStarted;
 
   late String executable;
   late List<String> processArgs;
@@ -57,7 +61,10 @@ class MockFlutterDebugAdapter extends FlutterDebugAdapter {
 
     // Pretend we launched the app and got the app.started event so that
     // launchRequest will complete.
-    appStartedCompleter.complete();
+    if (simulateAppStarted) {
+      appId = 'TEST';
+      appStartedCompleter.complete();
+    }
   }
 
   @override