add an error count field to the Flutter.Error event (#36768)

* add an error count field to the Flutter.Error event

* review comments; more tests

* normalize comments

packages/flutter/lib/src/widgets/widget_inspector.dart

@@ -908,8 +908,10 @@ mixin WidgetInspectorService {
 
   static const String _consoleObjectGroup = 'console-group';
 
+  int _errorsSinceReload = 0;
+
   void _reportError(FlutterErrorDetails details) {
-    postEvent('Flutter.Error', _nodeToJson(
+    final Map<String, Object> errorJson = _nodeToJson(
       details.toDiagnosticsNode(),
       _SerializationDelegate(
         groupName: _consoleObjectGroup,
@@ -919,7 +921,21 @@ mixin WidgetInspectorService {
         maxDescendentsTruncatableNode: 5,
         service: this,
       ),
-    ));
+    );
+
+    errorJson['errorsSinceReload'] = _errorsSinceReload;
+    _errorsSinceReload += 1;
+
+    postEvent('Flutter.Error', errorJson);
+  }
+
+  /// Resets the count of errors since the last hot reload.
+  ///
+  /// This data is sent to clients as part of the 'Flutter.Error' service
+  /// protocol event. Clients may choose to display errors received after the
+  /// first error differently.
+  void _resetErrorCount() {
+    _errorsSinceReload = 0;
   }
 
   /// Called to register service extensions.
@@ -1838,6 +1854,7 @@ mixin WidgetInspectorService {
   /// [BindingBase.reassembleApplication].
   void performReassemble() {
     _clearStats();
+    _resetErrorCount();
   }
 }
 

packages/flutter/test/widgets/widget_inspector_test.dart

@@ -8,11 +8,11 @@ import 'dart:math';
 import 'dart:ui' as ui;
 
 import 'package:flutter/foundation.dart';
+import 'package:flutter/gestures.dart' show DragStartBehavior;
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';
-import 'package:flutter/gestures.dart' show DragStartBehavior;
 
 // Start of block of code where widget creation location line numbers and
 // columns will impact whether tests pass.
@@ -2331,6 +2331,71 @@ class TestWidgetInspectorService extends Object with WidgetInspectorService {
       );
     }, skip: isBrowser);
 
+    testWidgets('ext.flutter.inspector.structuredErrors', (WidgetTester tester) async {
+      List<Map<Object, Object>> flutterErrorEvents = service.getEventsDispatched('Flutter.Error');
+      expect(flutterErrorEvents, isEmpty);
+
+      final FlutterExceptionHandler oldHandler = FlutterError.onError;
+
+      try {
+        // Enable structured errors.
+        expect(await service.testBoolExtension(
+            'structuredErrors', <String, String>{'enabled': 'true'}),
+            equals('true'));
+
+        // Create an error.
+        FlutterError.reportError(FlutterErrorDetailsForRendering(
+          library: 'rendering library',
+          context: ErrorDescription('during layout'),
+          exception: StackTrace.current,
+        ));
+
+        // Validate that we received an error.
+        flutterErrorEvents = service.getEventsDispatched('Flutter.Error');
+        expect(flutterErrorEvents, hasLength(1));
+
+        // Validate the error contents.
+        Map<Object, Object> error = flutterErrorEvents.first;
+        expect(error['description'], 'Exception caught by rendering library');
+        expect(error['children'], isEmpty);
+
+        // Validate that we received an error count.
+        expect(error['errorsSinceReload'], 0);
+
+        // Send a second error.
+        FlutterError.reportError(FlutterErrorDetailsForRendering(
+          library: 'rendering library',
+          context: ErrorDescription('also during layout'),
+          exception: StackTrace.current,
+        ));
+
+        // Validate that the error count increased.
+        flutterErrorEvents = service.getEventsDispatched('Flutter.Error');
+        expect(flutterErrorEvents, hasLength(2));
+        error = flutterErrorEvents.last;
+        expect(error['errorsSinceReload'], 1);
+
+        // Reload the app.
+        tester.binding.reassembleApplication();
+        await tester.pump();
+
+        // Send another error.
+        FlutterError.reportError(FlutterErrorDetailsForRendering(
+          library: 'rendering library',
+          context: ErrorDescription('during layout'),
+          exception: StackTrace.current,
+        ));
+
+        // And, validate that the error count has been reset.
+        flutterErrorEvents = service.getEventsDispatched('Flutter.Error');
+        expect(flutterErrorEvents, hasLength(3));
+        error = flutterErrorEvents.last;
+        expect(error['errorsSinceReload'], 0);
+      } finally {
+        FlutterError.onError = oldHandler;
+      }
+    });
+
     testWidgets('Screenshot of composited transforms - only offsets', (WidgetTester tester) async {
       // Composited transforms are challenging to take screenshots of as the
       // LeaderLayer and FollowerLayer classes used by CompositedTransformTarget