Test that inspector does not hold objects. (#130102)

packages/flutter/test/widgets/widget_inspector_test.dart

@@ -10,6 +10,7 @@
 library;
 
 import 'dart:convert';
+import 'dart:developer';
 import 'dart:math';
 import 'dart:ui' as ui;
 
@@ -240,6 +241,29 @@ extension TextFromString on String {
   }
 }
 
+/// Forces garbage collection by aggressive memory allocation.
+///
+/// Copied from internal code of
+/// https://github.com/dart-lang/leak_tracker
+Future<void> _forceGC() async {
+  const int gcCycles = 3; // 1 should be enough, but we do 3 to make sure test is not flaky.
+  final int barrier = reachabilityBarrier;
+
+  final List<List<DateTime>> storage = <List<DateTime>>[];
+
+  void allocateMemory() {
+    storage.add(Iterable<DateTime>.generate(10000, (_) => DateTime.now()).toList());
+    if (storage.length > 100) {
+      storage.removeAt(0);
+    }
+  }
+
+  while (reachabilityBarrier < barrier + gcCycles) {
+    await Future<void>.delayed(Duration.zero);
+    allocateMemory();
+  }
+}
+
 final List<Object> _weakValueTests = <Object>[1, 1.0, 'hello', true, false, Object(), <int>[3, 4], DateTime(2023)];
 
 void main() {
@@ -299,6 +323,19 @@ class _TestWidgetInspectorService extends TestWidgetInspectorService {
       expect(WidgetInspectorService.objectToDiagnosticsNode(Alignment.bottomCenter), isNull);
     });
 
+    test('WidgetInspector does not hold objects from GC', () async {
+      List<DateTime>? someObject = <DateTime>[DateTime.now(), DateTime.now()];
+      final String? id = service.toId(someObject, 'group_name');
+
+      expect(id, isNotNull);
+
+      final WeakReference<Object> ref = WeakReference<Object>(someObject);
+      someObject = null;
+      await _forceGC();
+
+      expect(ref.target, null);
+    });
+
     testWidgets('WidgetInspector smoke test', (WidgetTester tester) async {
       // This is a smoke test to verify that adding the inspector doesn't crash.
       await tester.pumpWidget(
@@ -3775,7 +3812,7 @@ class _TestWidgetInspectorService extends TestWidgetInspectorService {
       _CreationLocation location = knownLocations[id]!;
       expect(location.file, equals(file));
       // ClockText widget.
-      expect(location.line, equals(55));
+      expect(location.line, equals(56));
       expect(location.column, equals(9));
       expect(location.name, equals('ClockText'));
       expect(count, equals(1));
@@ -3785,7 +3822,7 @@ class _TestWidgetInspectorService extends TestWidgetInspectorService {
       location = knownLocations[id]!;
       expect(location.file, equals(file));
       // Text widget in _ClockTextState build method.
-      expect(location.line, equals(93));
+      expect(location.line, equals(94));
       expect(location.column, equals(12));
       expect(location.name, equals('Text'));
       expect(count, equals(1));
@@ -3812,7 +3849,7 @@ class _TestWidgetInspectorService extends TestWidgetInspectorService {
       location = knownLocations[id]!;
       expect(location.file, equals(file));
       // ClockText widget.
-      expect(location.line, equals(55));
+      expect(location.line, equals(56));
       expect(location.column, equals(9));
       expect(location.name, equals('ClockText'));
       expect(count, equals(3)); // 3 clock widget instances rebuilt.
@@ -3822,7 +3859,7 @@ class _TestWidgetInspectorService extends TestWidgetInspectorService {
       location = knownLocations[id]!;
       expect(location.file, equals(file));
       // Text widget in _ClockTextState build method.
-      expect(location.line, equals(93));
+      expect(location.line, equals(94));
       expect(location.column, equals(12));
       expect(location.name, equals('Text'));
       expect(count, equals(3)); // 3 clock widget instances rebuilt.