[flutter_tools/dap] Inform DAP client whether restart is supported (#121610)

[flutter_tools/dap] Inform DAP client whether restart is supported

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

@@ -48,13 +48,6 @@ class FlutterDebugAdapter extends FlutterBaseDebugAdapter {
   /// their handlers.
   final Map<int, Completer<Object?>> _flutterRequestCompleters = <int, Completer<Object?>>{};
 
-  /// Whether or not this adapter can handle the restartRequest.
-  ///
-  /// For Flutter apps we can handle this with a Hot Restart rather than having
-  /// the whole debug session stopped and restarted.
-  @override
-  bool get supportsRestartRequest => true;
-
   /// A list of reverse-requests from `flutter run --machine` that should be forwarded to the client.
   static const Set<String> _requestsToForwardToClient = <String>{
     // The 'app.exposeUrl' request is sent by Flutter to request the client
@@ -399,6 +392,12 @@ class FlutterDebugAdapter extends FlutterBaseDebugAdapter {
     if (_appId == null) {
       throw DebugAdapterException('Unexpected null `appId` in app.start event');
     }
+
+    // Notify the client whether it can call 'restartRequest' when the user
+    // clicks restart, instead of terminating and re-starting its own debug
+    // session (which is much slower, but required for profile/release mode).
+    final bool supportsRestart = (params['supportsRestart'] as bool?) ?? false;
+    sendEvent(CapabilitiesEventBody(capabilities: Capabilities(supportsRestartRequest: supportsRestart)));
   }
 
   /// Handles the app.started event from Flutter.

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

@@ -101,6 +101,44 @@ void main() {
         expect(adapter.pidsToTerminate, isNot(contains(123)));
       });
 
+
+      group('supportsRestartRequest', () {
+        void testRestartSupport(bool supportsRestart) {
+          test('notifies client for supportsRestart: $supportsRestart', () async {
+            final MockFlutterDebugAdapter adapter = MockFlutterDebugAdapter(
+              fileSystem: MemoryFileSystem.test(style: fsStyle),
+              platform: platform,
+              supportsRestart: supportsRestart,
+            );
+
+            final FlutterLaunchRequestArguments args = FlutterLaunchRequestArguments(
+              cwd: '/project',
+              program: 'foo.dart',
+            );
+
+            // Listen for a Capabilities event that modifies 'supportsRestartRequest'.
+            final Future<CapabilitiesEventBody> capabilitiesUpdate = adapter
+                .dapToClientMessages
+                .where((Map<String, Object?> message) => message['event'] == 'capabilities')
+                .map((Map<String, Object?> message) => message['body'] as Map<String, Object?>?)
+                .where((Map<String, Object?>? body) => body != null).cast<Map<String, Object?>>()
+                .map(CapabilitiesEventBody.fromJson)
+                .firstWhere((CapabilitiesEventBody body) => body.capabilities.supportsRestartRequest != null);
+
+            await adapter.configurationDoneRequest(MockRequest(), null, () {});
+            final Completer<void> launchCompleter = Completer<void>();
+            await adapter.launchRequest(MockRequest(), args, launchCompleter.complete);
+            await launchCompleter.future;
+
+            // Ensure the Capabilities update has the expected value.
+            expect((await capabilitiesUpdate).capabilities.supportsRestartRequest, supportsRestart);
+          });
+        }
+
+        testRestartSupport(true);
+        testRestartSupport(false);
+      });
+
       test('calls "app.stop" on terminateRequest', () async {
         final MockFlutterDebugAdapter adapter = MockFlutterDebugAdapter(
           fileSystem: MemoryFileSystem.test(style: fsStyle),

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

@@ -18,6 +18,7 @@ class MockFlutterDebugAdapter extends FlutterDebugAdapter {
     required FileSystem fileSystem,
     required Platform platform,
     bool simulateAppStarted = true,
+    bool supportsRestart = true,
     FutureOr<void> Function(MockFlutterDebugAdapter adapter)? preAppStart,
   }) {
     final StreamController<List<int>> stdinController = StreamController<List<int>>();
@@ -31,6 +32,7 @@ class MockFlutterDebugAdapter extends FlutterDebugAdapter {
       fileSystem: fileSystem,
       platform: platform,
       simulateAppStarted: simulateAppStarted,
+      supportsRestart: supportsRestart,
       preAppStart: preAppStart,
     );
   }
@@ -41,6 +43,7 @@ class MockFlutterDebugAdapter extends FlutterDebugAdapter {
     required super.fileSystem,
     required super.platform,
     this.simulateAppStarted = true,
+    this.supportsRestart = true,
     this.preAppStart,
   }) {
     clientChannel.listen((ProtocolMessage message) {
@@ -51,6 +54,7 @@ class MockFlutterDebugAdapter extends FlutterDebugAdapter {
   int _seq = 1;
   final ByteStreamServerChannel clientChannel;
   final bool simulateAppStarted;
+  final bool supportsRestart;
   final FutureOr<void> Function(MockFlutterDebugAdapter adapter)? preAppStart;
 
   late String executable;
@@ -110,6 +114,7 @@ class MockFlutterDebugAdapter extends FlutterDebugAdapter {
         'event': 'app.start',
         'params': <String, Object?>{
           'appId': 'TEST',
+          'supportsRestart': supportsRestart,
         }
       });
     }