TwoDimensionalChildDelegate should dispatch creation and disposal events (#145684)

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

@@ -885,6 +885,13 @@ Widget _createErrorWidget(Object exception, StackTrace stackTrace) {
 ///   * [TwoDimensionalChildListDelegate], an concrete subclass of this that
 ///     uses a two dimensional array to layout children.
 abstract class TwoDimensionalChildDelegate extends ChangeNotifier {
+  /// Creates a delegate that supplies children for scrolling in two dimensions.
+  TwoDimensionalChildDelegate() {
+    if (kFlutterMemoryAllocationsEnabled) {
+      ChangeNotifier.maybeDispatchObjectCreation(this);
+    }
+  }
+
   /// Returns the child with the given [ChildVicinity], which is described in
   /// terms of x and y indices.
   ///

packages/flutter/test/widgets/ensure_visible_test.dart

@@ -7,7 +7,6 @@ import 'dart:math' as math;
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';
-import 'package:leak_tracker_flutter_testing/leak_tracker_flutter_testing.dart';
 
 import 'two_dimensional_utils.dart';
 
@@ -1063,10 +1062,7 @@ void main() {
       return tester.element(findKey(vicinity));
     }
 
-    testWidgets('Axis.vertical',
-    // TODO(polina-c): RenderTwoDimensionalViewport should dispose _delegate https://github.com/flutter/flutter/issues/145628 [leaks-to-clean]
-    experimentalLeakTesting: LeakTesting.settings.withIgnoredAll(),
-    (WidgetTester tester) async {
+    testWidgets('Axis.vertical', (WidgetTester tester) async {
       await tester.pumpWidget(simpleBuilderTest(useCacheExtent: true));
 
       Scrollable.ensureVisible(findContext(

packages/flutter/test/widgets/scroll_delegate_test.dart

@@ -0,0 +1,29 @@
+// Copyright 2014 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:leak_tracker_flutter_testing/leak_tracker_flutter_testing.dart';
+
+void main() {
+  test('TwoDimensionalChildBuilderDelegate dispatches memory events', () async {
+    await expectLater(
+      await memoryEvents(
+        () => TwoDimensionalChildBuilderDelegate(builder: (_, __) => null).dispose(),
+        TwoDimensionalChildBuilderDelegate,
+      ),
+      areCreateAndDispose,
+    );
+  });
+
+  test('TwoDimensionalChildListDelegate dispatches memory events', () async {
+    await expectLater(
+      await memoryEvents(
+        () => TwoDimensionalChildListDelegate(children: <List<Widget>>[]).dispose(),
+        TwoDimensionalChildListDelegate,
+      ),
+      areCreateAndDispose,
+    );
+  });
+}

packages/flutter/test/widgets/two_dimensional_scroll_view_test.dart

@@ -360,6 +360,8 @@ void main() {
       addTearDown(verticalController.dispose);
       final ScrollController horizontalController = ScrollController();
       addTearDown(horizontalController.dispose);
+      late final TwoDimensionalChildBuilderDelegate delegate;
+      addTearDown(() => delegate.dispose());
 
       await tester.pumpWidget(
         Directionality(
@@ -368,7 +370,7 @@ void main() {
             verticalDetails: ScrollableDetails.vertical(controller: verticalController),
             horizontalDetails: ScrollableDetails.horizontal(controller: horizontalController),
             diagonalDragBehavior: DiagonalDragBehavior.free,
-            delegate: TwoDimensionalChildBuilderDelegate(
+            delegate: delegate = TwoDimensionalChildBuilderDelegate(
               maxXIndex: 100,
               maxYIndex: 100,
               builder: (BuildContext context, ChildVicinity vicinity) {
@@ -503,6 +505,8 @@ void main() {
       addTearDown(verticalController.dispose);
       final ScrollController horizontalController = ScrollController();
       addTearDown(horizontalController.dispose);
+      late final TwoDimensionalChildBuilderDelegate delegate;
+      addTearDown(() => delegate.dispose());
 
       await tester.pumpWidget(
         Directionality(
@@ -511,7 +515,7 @@ void main() {
             verticalDetails: ScrollableDetails.vertical(controller: verticalController),
             horizontalDetails: ScrollableDetails.horizontal(controller: horizontalController),
             diagonalDragBehavior: DiagonalDragBehavior.free,
-            delegate: TwoDimensionalChildBuilderDelegate(
+            delegate: delegate = TwoDimensionalChildBuilderDelegate(
               maxXIndex: 100,
               maxYIndex: 100,
               builder: (BuildContext context, ChildVicinity vicinity) {
@@ -588,6 +592,8 @@ void main() {
         addTearDown(verticalController.dispose);
         final ScrollController horizontalController = ScrollController();
         addTearDown(horizontalController.dispose);
+        late final TwoDimensionalChildBuilderDelegate delegate;
+        addTearDown(() => delegate.dispose());
 
         await tester.pumpWidget(
           Directionality(
@@ -596,7 +602,7 @@ void main() {
               verticalDetails: ScrollableDetails.vertical(controller: verticalController),
               horizontalDetails: ScrollableDetails.horizontal(controller: horizontalController),
               diagonalDragBehavior: DiagonalDragBehavior.free,
-              delegate: TwoDimensionalChildBuilderDelegate(
+              delegate: delegate = TwoDimensionalChildBuilderDelegate(
                 maxXIndex: 20,
                 maxYIndex: 1,
                 builder: _testChildBuilder,
@@ -636,6 +642,8 @@ void main() {
         addTearDown(verticalController.dispose);
         final ScrollController horizontalController = ScrollController();
         addTearDown(horizontalController.dispose);
+        late final TwoDimensionalChildBuilderDelegate delegate;
+        addTearDown(() => delegate.dispose());
 
         await tester.pumpWidget(
           Directionality(
@@ -644,7 +652,7 @@ void main() {
               verticalDetails: ScrollableDetails.vertical(controller: verticalController),
               horizontalDetails: ScrollableDetails.horizontal(controller: horizontalController),
               diagonalDragBehavior: DiagonalDragBehavior.weightedEvent,
-              delegate: TwoDimensionalChildBuilderDelegate(
+              delegate: delegate = TwoDimensionalChildBuilderDelegate(
                 maxXIndex: 20,
                 maxYIndex: 1,
                 builder: _testChildBuilder,
@@ -684,6 +692,8 @@ void main() {
         addTearDown(verticalController.dispose);
         final ScrollController horizontalController = ScrollController();
         addTearDown(horizontalController.dispose);
+        late final TwoDimensionalChildBuilderDelegate delegate;
+        addTearDown(() => delegate.dispose());
 
         await tester.pumpWidget(
           Directionality(
@@ -692,7 +702,7 @@ void main() {
               verticalDetails: ScrollableDetails.vertical(controller: verticalController),
               horizontalDetails: ScrollableDetails.horizontal(controller: horizontalController),
               diagonalDragBehavior: DiagonalDragBehavior.weightedContinuous,
-              delegate: TwoDimensionalChildBuilderDelegate(
+              delegate: delegate = TwoDimensionalChildBuilderDelegate(
                 maxXIndex: 20,
                 maxYIndex: 1,
                 builder: _testChildBuilder,
@@ -734,6 +744,8 @@ void main() {
         addTearDown(verticalController.dispose);
         final ScrollController horizontalController = ScrollController();
         addTearDown(horizontalController.dispose);
+        late final TwoDimensionalChildBuilderDelegate delegate;
+        addTearDown(() => delegate.dispose());
 
         await tester.pumpWidget(
           Directionality(
@@ -742,7 +754,7 @@ void main() {
               verticalDetails: ScrollableDetails.vertical(controller: verticalController),
               horizontalDetails: ScrollableDetails.horizontal(controller: horizontalController),
               diagonalDragBehavior: DiagonalDragBehavior.free,
-              delegate: TwoDimensionalChildBuilderDelegate(
+              delegate: delegate = TwoDimensionalChildBuilderDelegate(
                 maxXIndex: 1,
                 maxYIndex: 20,
                 builder: _testChildBuilder,
@@ -782,6 +794,8 @@ void main() {
         addTearDown(verticalController.dispose);
         final ScrollController horizontalController = ScrollController();
         addTearDown(horizontalController.dispose);
+        late final TwoDimensionalChildBuilderDelegate delegate;
+        addTearDown(() => delegate.dispose());
 
         await tester.pumpWidget(
           Directionality(
@@ -790,7 +804,7 @@ void main() {
               verticalDetails: ScrollableDetails.vertical(controller: verticalController),
               horizontalDetails: ScrollableDetails.horizontal(controller: horizontalController),
               diagonalDragBehavior: DiagonalDragBehavior.weightedEvent,
-              delegate: TwoDimensionalChildBuilderDelegate(
+              delegate: delegate = TwoDimensionalChildBuilderDelegate(
                 maxXIndex: 1,
                 maxYIndex: 20,
                 builder: _testChildBuilder,
@@ -830,6 +844,8 @@ void main() {
         addTearDown(verticalController.dispose);
         final ScrollController horizontalController = ScrollController();
         addTearDown(horizontalController.dispose);
+        late final TwoDimensionalChildBuilderDelegate delegate;
+        addTearDown(() => delegate.dispose());
 
         await tester.pumpWidget(
           Directionality(
@@ -838,7 +854,7 @@ void main() {
               verticalDetails: ScrollableDetails.vertical(controller: verticalController),
               horizontalDetails: ScrollableDetails.horizontal(controller: horizontalController),
               diagonalDragBehavior: DiagonalDragBehavior.weightedContinuous,
-              delegate: TwoDimensionalChildBuilderDelegate(
+              delegate: delegate = TwoDimensionalChildBuilderDelegate(
                 maxXIndex: 1,
                 maxYIndex: 20,
                 builder: _testChildBuilder,

packages/flutter/test/widgets/two_dimensional_viewport_test.dart

@@ -335,6 +335,7 @@ void main() {
             );
           }
         );
+        addTearDown(builderDelegate.dispose);
 
         await tester.pumpWidget(simpleBuilderTest(
           delegate: builderDelegate,