Migrate even more Material framework tests to null safety. (#67849)

packages/flutter/test/widgets/fractionally_sized_box_test.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';
@@ -27,7 +25,7 @@ void main() {
         ),
       ),
     ));
-    final RenderBox box = inner.currentContext.findRenderObject() as RenderBox;
+    final RenderBox box = inner.currentContext!.findRenderObject()! as RenderBox;
     expect(box.size, equals(const Size(50.0, 25.0)));
     expect(box.localToGlobal(Offset.zero), equals(const Offset(25.0, 37.5)));
   });
@@ -43,7 +41,7 @@ void main() {
         child: Placeholder(key: inner),
       ),
     ));
-    final RenderBox box = inner.currentContext.findRenderObject() as RenderBox;
+    final RenderBox box = inner.currentContext!.findRenderObject()! as RenderBox;
     expect(box.size, equals(const Size(400.0, 300.0)));
     expect(box.localToGlobal(box.size.center(Offset.zero)), equals(const Offset(800.0 - 400.0 / 2.0, 0.0 + 300.0 / 2.0)));
   });
@@ -59,7 +57,7 @@ void main() {
         child: Placeholder(key: inner),
       ),
     ));
-    final RenderBox box = inner.currentContext.findRenderObject() as RenderBox;
+    final RenderBox box = inner.currentContext!.findRenderObject()! as RenderBox;
     expect(box.size, equals(const Size(400.0, 300.0)));
     expect(box.localToGlobal(box.size.center(Offset.zero)), equals(const Offset(0.0 + 400.0 / 2.0, 0.0 + 300.0 / 2.0)));
   });
@@ -85,7 +83,7 @@ void main() {
         ),
       ),
     ));
-    final RenderBox box = inner.currentContext.findRenderObject() as RenderBox;
+    final RenderBox box = inner.currentContext!.findRenderObject()! as RenderBox;
     expect(box.size, equals(const Size(50.0, 25.0)));
     expect(box.localToGlobal(Offset.zero), equals(const Offset(25.0, 37.5)));
   });

packages/flutter/test/widgets/gesture_detector_test.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter/rendering.dart';
@@ -14,7 +12,7 @@ void main() {
 
   testWidgets('Uncontested scrolls start immediately', (WidgetTester tester) async {
     bool didStartDrag = false;
-    double updatedDragDelta;
+    double? updatedDragDelta;
     bool didEndDrag = false;
 
     final Widget widget = GestureDetector(
@@ -69,7 +67,7 @@ void main() {
 
     final Widget widget = GestureDetector(
       dragStartBehavior: DragStartBehavior.down,
-      onVerticalDragUpdate: (DragUpdateDetails details) { dragDistance += details.primaryDelta; },
+      onVerticalDragUpdate: (DragUpdateDetails details) { dragDistance += details.primaryDelta ?? 0; },
       onVerticalDragEnd: (DragEndDetails details) { gestureCount += 1; },
       onHorizontalDragUpdate: (DragUpdateDetails details) { fail('gesture should not match'); },
       onHorizontalDragEnd: (DragEndDetails details) { fail('gesture should not match'); },
@@ -95,7 +93,7 @@ void main() {
 
   testWidgets("Pan doesn't crash", (WidgetTester tester) async {
     bool didStartPan = false;
-    Offset panDelta;
+    Offset? panDelta;
     bool didEndPan = false;
 
     await tester.pumpWidget(
@@ -104,7 +102,7 @@ void main() {
           didStartPan = true;
         },
         onPanUpdate: (DragUpdateDetails details) {
-          panDelta = panDelta == null ? details.delta : panDelta + details.delta;
+          panDelta = (panDelta ?? Offset.zero) + details.delta;
         },
         onPanEnd: (DragEndDetails details) {
           didEndPan = true;
@@ -122,8 +120,8 @@ void main() {
     await tester.dragFrom(const Offset(10.0, 10.0), const Offset(20.0, 30.0));
 
     expect(didStartPan, isTrue);
-    expect(panDelta.dx, 20.0);
-    expect(panDelta.dy, 30.0);
+    expect(panDelta!.dx, 20.0);
+    expect(panDelta!.dy, 30.0);
     expect(didEndPan, isTrue);
   });
 
@@ -141,7 +139,7 @@ void main() {
       bool didReceivePointerDown;
       bool didTap;
 
-      Future<void> pumpWidgetTree(HitTestBehavior behavior) {
+      Future<void> pumpWidgetTree(HitTestBehavior? behavior) {
         return tester.pumpWidget(
           Directionality(
             textDirection: TextDirection.ltr,
@@ -732,7 +730,7 @@ void main() {
       await tester.pumpWidget(RawGestureDetector(
         key: key,
       ));
-      key.currentState.debugFillProperties(builder);
+      key.currentState!.debugFillProperties(builder);
 
       final List<String> description = builder.properties
         .where((DiagnosticsNode node) => !node.isFiltered(DiagnosticLevel.info))
@@ -767,7 +765,7 @@ void main() {
         child: Container(),
         semantics: _EmptySemanticsGestureDelegate(),
       ));
-      key.currentState.debugFillProperties(builder);
+      key.currentState!.debugFillProperties(builder);
 
       final List<String> description = builder.properties
         .where((DiagnosticsNode node) => !node.isFiltered(DiagnosticLevel.info))
@@ -791,7 +789,7 @@ void main() {
         semantics: _EmptySemanticsGestureDelegate(),
         excludeFromSemantics: true,
       ));
-      key.currentState.debugFillProperties(builder);
+      key.currentState!.debugFillProperties(builder);
 
       final List<String> description = builder.properties
         .where((DiagnosticsNode node) => !node.isFiltered(DiagnosticLevel.info))
@@ -806,13 +804,12 @@ void main() {
 
     group('error control test', () {
       test('constructor redundant pan and scale', () {
-        FlutterError error;
+        late FlutterError error;
         try {
           GestureDetector(onScaleStart: (_) {}, onPanStart: (_) {},);
         } on FlutterError catch (e) {
           error = e;
         } finally {
-          expect(error, isNotNull);
           expect(
             error.toStringDeep(),
             'FlutterError\n'
@@ -832,7 +829,7 @@ void main() {
       });
 
       test('constructor duplicate drag recognizer', () {
-        FlutterError error;
+        late FlutterError error;
         try {
           GestureDetector(
             onVerticalDragStart: (_) {},
@@ -842,7 +839,6 @@ void main() {
         } on FlutterError catch (e) {
           error = e;
         } finally {
-          expect(error, isNotNull);
           expect(
             error.toStringDeep(),
             'FlutterError\n'
@@ -868,14 +864,13 @@ void main() {
             ),
           ),
         );
-        FlutterError error;
+        late FlutterError error;
         try {
-          key.currentState.replaceGestureRecognizers(
+          key.currentState!.replaceGestureRecognizers(
             <Type, GestureRecognizerFactory>{});
         } on FlutterError catch (e) {
           error = e;
         } finally {
-          expect(error, isNotNull);
           expect(error.diagnostics.last.level, DiagnosticLevel.hint);
           expect(
             error.diagnostics.last.toStringDeep(),
@@ -913,8 +908,8 @@ class _EmptySemanticsGestureDelegate extends SemanticsGestureDelegate {
 /// A [TestVariant] that runs tests multiple times with different buttons.
 class ButtonVariant extends TestVariant<int> {
   const ButtonVariant({
-    @required this.values,
-    @required this.descriptions,
+    required this.values,
+    required this.descriptions,
   }) : assert(values.length != 0); // ignore: prefer_is_empty
 
   @override
@@ -922,12 +917,12 @@ class ButtonVariant extends TestVariant<int> {
 
   final Map<int, String> descriptions;
 
-  static int button;
+  static int button = 0;
 
   @override
   String describeValue(int value) {
     assert(descriptions.containsKey(value), 'Unknown button');
-    return descriptions[value];
+    return descriptions[value]!;
   }
 
   @override

packages/flutter/test/widgets/gesture_disambiguation_test.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter/gestures.dart';

packages/flutter/test/widgets/global_keys_duplicated_test.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter/foundation.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
@@ -61,7 +59,7 @@ void main() {
   });
 
   testWidgets('GlobalKey children of two nodes', (WidgetTester tester) async {
-    StateSetter nestedSetState;
+    late StateSetter nestedSetState;
     bool flag = false;
     await tester.pumpWidget(Stack(
       textDirection: TextDirection.ltr,

packages/flutter/test/widgets/global_keys_moving_test.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 
@@ -17,7 +15,7 @@ class Item {
 List<Item> items = <Item>[Item(), Item()];
 
 class StatefulLeaf extends StatefulWidget {
-  const StatefulLeaf({ GlobalKey key }) : super(key: key);
+  const StatefulLeaf({ GlobalKey? key }) : super(key: key);
 
   @override
   StatefulLeafState createState() => StatefulLeafState();
@@ -31,7 +29,7 @@ class StatefulLeafState extends State<StatefulLeaf> {
 }
 
 class KeyedWrapper extends StatelessWidget {
-  const KeyedWrapper(this.key1, this.key2, { Key key }) : super(key: key);
+  const KeyedWrapper(this.key1, this.key2, { Key? key }) : super(key: key);
 
   final Key key1;
   final GlobalKey key2;

packages/flutter/test/widgets/grid_paper_test.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/grid_view_layout_test.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/widgets/grid_view_test.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter/rendering.dart';
@@ -578,8 +576,7 @@ void main() {
         itemCount: 1000,
         gridDelegate: const SliverGridDelegateWithFixedCrossAxisCount(crossAxisCount: 3),
         itemBuilder: (BuildContext context, int index) {
-          counters[index] ??= 0;
-          counters[index] += 1;
+          counters[index] = (counters[index] ?? 0) + 1;
           return SizedBox(
             key: ValueKey<int>(index),
             width: 200,