[google_maps_flutter_web] Gracefully bypass HeatmapLayer when unsupported by Maps JS SDK

Google Maps JS API version 3.65 deprecated and completely removed the
HeatmapLayer constructor. To resolve the resulting runtime crashes on the
web platform, this change implements a dynamic, strongly-typed feature-detection
helper (isHeatmapSupported()) inside dom_window_extension.dart using standard
nullable JS interop extensions.

The HeatmapsController is shielded to return early and log a deduplicated warning
message on the console via debugPrint at most once per controller lifecycle, making
heatmap operations safe no-ops in 3.65+ environments.

The web integration tests (shape_test.dart and shapes_test.dart) are updated to import
dom_window_extension.dart directly and dynamically skip the heatmap controller test
groups when the class is not supported by the browser environment.

Author: jeffkwoh

packages/google_maps_flutter/google_maps_flutter_web/CHANGELOG.md

@@ -1,5 +1,6 @@
 ## NEXT
 
+* Gracefully bypasses `HeatmapLayer` instantiation and operations when unsupported by the loaded Google Maps JavaScript API (version 3.65+), preventing runtime web crashes.
 * Updates minimum supported SDK version to Flutter 3.38/Dart 3.10.
 
 ## 0.6.2+1

packages/google_maps_flutter/google_maps_flutter_web/example/integration_test/shape_test.dart

@@ -8,8 +8,12 @@ import 'dart:js_interop';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:google_maps/google_maps.dart' as gmaps;
 import 'package:google_maps/google_maps_visualization.dart' as visualization;
+import 'package:google_maps_flutter_platform_interface/google_maps_flutter_platform_interface.dart';
 import 'package:google_maps_flutter_web/google_maps_flutter_web.dart';
 import 'package:integration_test/integration_test.dart';
+import 'package:web/web.dart' as web;
+
+import 'shared_mocks.dart';
 
 /// Test Shapes (Circle, Polygon, Polyline)
 void main() {
@@ -203,47 +207,109 @@ void main() {
   });
 
   group('HeatmapController', () {
-    late visualization.HeatmapLayer heatmap;
+    group('Heatmap on Google Maps JS SDK v3.64 (Supported)', () {
+      late visualization.HeatmapLayer heatmap;
+      late JSObject? originalHeatmapLayer;
+      late JSObject? visualizationNamespace;
 
-    setUp(() {
-      heatmap = visualization.HeatmapLayer();
-    });
+      setUp(() {
+        injectMockHeatmapLayer();
 
-    testWidgets('update', (WidgetTester tester) async {
-      final controller = HeatmapController(heatmap: heatmap);
-      final options = visualization.HeatmapLayerOptions()
-        ..data = <gmaps.LatLng>[gmaps.LatLng(0, 0)].toJS;
+        final JSObject? google = web.window.nullableGoogle;
+        final JSObject? maps = google!.nullableMaps;
+        visualizationNamespace = maps!.nullableVisualization;
+        originalHeatmapLayer = visualizationNamespace?.nullableHeatmapLayer;
 
-      expect(heatmap.data.array.toDart, hasLength(0));
+        visualizationNamespace?.nullableHeatmapLayer =
+            web.window.mockHeatmapLayer;
 
-      controller.update(options);
+        heatmap = visualization.HeatmapLayer();
+      });
+
+      tearDown(() {
+        if (visualizationNamespace != null) {
+          visualizationNamespace!.nullableHeatmapLayer = originalHeatmapLayer;
+        }
+      });
+
+      testWidgets('update', (WidgetTester tester) async {
+        final controller = HeatmapController(heatmap: heatmap);
+        final options = visualization.HeatmapLayerOptions()
+          ..data = <gmaps.LatLng>[gmaps.LatLng(0, 0)].toJS;
+
+        expect(heatmap.data.array.toDart, hasLength(0));
+
+        controller.update(options);
+
+        expect(heatmap.data.array.toDart, hasLength(1));
+      });
+
+      group('remove', () {
+        late HeatmapController controller;
+
+        setUp(() {
+          controller = HeatmapController(heatmap: heatmap);
+        });
 
-      expect(heatmap.data.array.toDart, hasLength(1));
+        testWidgets('drops gmaps instance', (WidgetTester tester) async {
+          controller.remove();
+
+          expect(controller.heatmap, isNull);
+        });
+
+        testWidgets('cannot call update after remove', (
+          WidgetTester tester,
+        ) async {
+          final options = visualization.HeatmapLayerOptions()
+            ..dissipating = true;
+
+          controller.remove();
+
+          expect(() {
+            controller.update(options);
+          }, throwsAssertionError);
+        });
+      });
     });
 
-    group('remove', () {
-      late HeatmapController controller;
+    group('Heatmap on Google Maps JS SDK v3.65 (Unsupported)', () {
+      late JSObject? originalHeatmapLayer;
+      late JSObject? visualizationNamespace;
 
       setUp(() {
-        controller = HeatmapController(heatmap: heatmap);
+        final JSObject? google = web.window.nullableGoogle;
+        final JSObject? maps = google!.nullableMaps;
+        visualizationNamespace = maps!.nullableVisualization;
+        originalHeatmapLayer = visualizationNamespace?.nullableHeatmapLayer;
       });
 
-      testWidgets('drops gmaps instance', (WidgetTester tester) async {
-        controller.remove();
-
-        expect(controller.heatmap, isNull);
+      tearDown(() {
+        if (visualizationNamespace != null) {
+          visualizationNamespace!.nullableHeatmapLayer = originalHeatmapLayer;
+        }
       });
 
-      testWidgets('cannot call update after remove', (
+      testWidgets('gracefully bypasses and logs warning exactly once', (
         WidgetTester tester,
       ) async {
-        final options = visualization.HeatmapLayerOptions()..dissipating = true;
-
-        controller.remove();
-
-        expect(() {
-          controller.update(options);
-        }, throwsAssertionError);
+        final controller = HeatmapsController();
+        final map = gmaps.Map(
+          web.document.createElement('div') as web.HTMLDivElement,
+        );
+        controller.bindToMap(123, map);
+
+        final heatmaps = <Heatmap>{
+          const Heatmap(
+            heatmapId: HeatmapId('1'),
+            data: <WeightedLatLng>[],
+            radius: HeatmapRadius.fromPixels(20),
+          ),
+        };
+
+        controller.addHeatmaps(heatmaps);
+
+        expect(controller.heatmaps.isEmpty, isTrue);
+        expect(controller.pendingHeatmaps.length, 1);
       });
     });
   });