Pass app.started events to the DAP client + dart.debuggerUris for Profile mode (#106337)

Author: DanTup

packages/flutter_tools/lib/src/debug_adapters/README.md

@@ -70,6 +70,10 @@ Some custom requests are available for clients to call. Below are the Flutter-sp
 
 The debug adapter may emit several custom events that are useful to clients. Below are the Flutter-specific custom events, and the standard Dart DAP custom events are [documented here](https://github.com/dart-lang/sdk/blob/main/pkg/dds/tool/dap/README.md#custom-events).
 
+### `flutter.appStarted`
+
+This event is emitted when the application has started up. Unlike `dart.debuggerUris`, this event occurs even for `noDebug` launches or those that do not include a VM Service.
+
 ### `flutter.serviceExtensionStateChanged`
 
 When the value of a Flutter service extension changes, this event is emitted and includes the new value. Values are always encoded as strings, even if numeric/boolean.

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

@@ -397,8 +397,25 @@ class FlutterDebugAdapter extends DartDebugAdapter<FlutterLaunchRequestArguments
   /// 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) {
-      connectDebugger(serviceUri, resumeIfStarting: true);
+      if (enableDebugger) {
+        connectDebugger(serviceUri, resumeIfStarting: true);
+      } else {
+        // Usually, `connectDebugger` (in the base Dart adapter) will send this
+        // event when it connects a debugger. Since we're not connecting a
+        // debugger we send this ourselves, to allow clients to connect to the
+        // VM Service for things like starting DevTools, even if debugging is
+        // not available.
+        // TODO(dantup): Switch this to call `sendDebuggerUris()` on the base
+        //   adapter once rolled into Flutter.
+        sendEvent(
+          RawEventBody(<String, Object?>{
+            'vmServiceUri': serviceUri.toString(),
+          }),
+          eventType: 'dart.debuggerUris',
+        );
+      }
     }
   }
 
@@ -412,6 +429,15 @@ class FlutterDebugAdapter extends DartDebugAdapter<FlutterLaunchRequestArguments
   void _handleAppStarted() {
     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.
+    sendEvent(
+      RawEventBody(<String, Object?>{}),
+      eventType: 'flutter.appStarted',
+    );
   }
 
   /// Handles the daemon.connected event, recording the pid of the flutter_tools process.
@@ -427,12 +453,6 @@ 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) {
-    // When running in noDebug mode, Flutter may still provide us a VM Service
-    // URI, but we will not connect it because we don't want to do any debugging.
-    if (!enableDebugger) {
-      return;
-    }
-
     // 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) {

packages/flutter_tools/test/integration.shard/debug_adapter/flutter_adapter_test.dart

@@ -302,6 +302,24 @@ void main() {
 
       await dap.client.terminate();
     });
+
+    testWithoutContext('provides appStarted events to the client', () async {
+      final BasicProject project = BasicProject();
+      await project.setUpIn(tempDir);
+
+      // Launch the app and wait for it to send a 'flutter.appStarted' event.
+      await Future.wait(<Future<void>>[
+        dap.client.event('flutter.appStarted'),
+        dap.client.start(
+          launch: () => dap.client.launch(
+            cwd: project.dir.path,
+            toolArgs: <String>['-d', 'flutter-tester'],
+          ),
+        ),
+      ], eagerError: true);
+
+      await dap.client.terminate();
+    });
   });
 
   group('attach', () {