Fix ScrollBehavior copyWith (#91834)

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

@@ -85,19 +85,21 @@ class ScrollBehavior {
   /// the widget level, like [PageView.scrollBehavior], in order to change the
   /// default.
   ScrollBehavior copyWith({
-    bool scrollbars = true,
-    bool overscroll = true,
+    bool? scrollbars,
+    bool? overscroll,
     Set<PointerDeviceKind>? dragDevices,
     ScrollPhysics? physics,
     TargetPlatform? platform,
+    AndroidOverscrollIndicator? androidOverscrollIndicator,
   }) {
     return _WrappedScrollBehavior(
       delegate: this,
-      scrollbar: scrollbars,
-      overscrollIndicator: overscroll,
+      scrollbars: scrollbars ?? true,
+      overscroll: overscroll ?? true,
       physics: physics,
       platform: platform,
       dragDevices: dragDevices,
+      androidOverscrollIndicator: androidOverscrollIndicator
     );
   }
 
@@ -251,38 +253,40 @@ class ScrollBehavior {
 class _WrappedScrollBehavior implements ScrollBehavior {
   const _WrappedScrollBehavior({
     required this.delegate,
-    this.scrollbar = true,
-    this.overscrollIndicator = true,
+    this.scrollbars = true,
+    this.overscroll = true,
     this.physics,
     this.platform,
     Set<PointerDeviceKind>? dragDevices,
-  }) : _dragDevices = dragDevices;
+    AndroidOverscrollIndicator? androidOverscrollIndicator,
+  }) : _androidOverscrollIndicator = androidOverscrollIndicator,
+       _dragDevices = dragDevices;
 
   final ScrollBehavior delegate;
-  final bool scrollbar;
-  final bool overscrollIndicator;
+  final bool scrollbars;
+  final bool overscroll;
   final ScrollPhysics? physics;
   final TargetPlatform? platform;
   final Set<PointerDeviceKind>? _dragDevices;
+  @override
+  final AndroidOverscrollIndicator? _androidOverscrollIndicator;
 
   @override
   Set<PointerDeviceKind> get dragDevices => _dragDevices ?? delegate.dragDevices;
 
   @override
-  AndroidOverscrollIndicator get androidOverscrollIndicator => delegate.androidOverscrollIndicator;
-  @override
-  AndroidOverscrollIndicator? get _androidOverscrollIndicator => throw UnimplementedError();
+  AndroidOverscrollIndicator get androidOverscrollIndicator => _androidOverscrollIndicator ?? delegate.androidOverscrollIndicator;
 
   @override
   Widget buildOverscrollIndicator(BuildContext context, Widget child, ScrollableDetails details) {
-    if (overscrollIndicator)
+    if (overscroll)
       return delegate.buildOverscrollIndicator(context, child, details);
     return child;
   }
 
   @override
   Widget buildScrollbar(BuildContext context, Widget child, ScrollableDetails details) {
-    if (scrollbar)
+    if (scrollbars)
       return delegate.buildScrollbar(context, child, details);
     return child;
   }
@@ -294,19 +298,20 @@ class _WrappedScrollBehavior implements ScrollBehavior {
 
   @override
   ScrollBehavior copyWith({
-    bool scrollbars = true,
-    bool overscroll = true,
+    bool? scrollbars,
+    bool? overscroll,
     ScrollPhysics? physics,
     TargetPlatform? platform,
     Set<PointerDeviceKind>? dragDevices,
     AndroidOverscrollIndicator? androidOverscrollIndicator
   }) {
     return delegate.copyWith(
-      scrollbars: scrollbars,
-      overscroll: overscroll,
-      physics: physics,
-      platform: platform,
-      dragDevices: dragDevices,
+      scrollbars: scrollbars ?? this.scrollbars,
+      overscroll: overscroll ?? this.overscroll,
+      physics: physics ?? this.physics,
+      platform: platform ?? this.platform,
+      dragDevices: dragDevices ?? this.dragDevices,
+      androidOverscrollIndicator: androidOverscrollIndicator ?? this.androidOverscrollIndicator,
     );
   }
 
@@ -323,8 +328,8 @@ class _WrappedScrollBehavior implements ScrollBehavior {
   @override
   bool shouldNotify(_WrappedScrollBehavior oldDelegate) {
     return oldDelegate.delegate.runtimeType != delegate.runtimeType
-        || oldDelegate.scrollbar != scrollbar
-        || oldDelegate.overscrollIndicator != overscrollIndicator
+        || oldDelegate.scrollbars != scrollbars
+        || oldDelegate.overscroll != overscroll
         || oldDelegate.physics != physics
         || oldDelegate.platform != platform
         || setEquals<PointerDeviceKind>(oldDelegate.dragDevices, dragDevices)

packages/flutter/test/widgets/scroll_behavior_test.dart

@@ -125,4 +125,181 @@ void main() {
     expect(find.byType(StretchingOverscrollIndicator), findsOneWidget);
     expect(find.byType(GlowingOverscrollIndicator), findsNothing);
   }, variant: TargetPlatformVariant.only(TargetPlatform.android));
+
+  group('ScrollBehavior configuration is maintained over multiple copies', () {
+    testWidgets('dragDevices', (WidgetTester tester) async {
+      // Regression test for https://github.com/flutter/flutter/issues/91673
+      const ScrollBehavior defaultBehavior = ScrollBehavior();
+      expect(defaultBehavior.dragDevices, <PointerDeviceKind>{
+        PointerDeviceKind.touch,
+        PointerDeviceKind.stylus,
+        PointerDeviceKind.invertedStylus,
+      });
+
+      // Use copyWith to modify drag devices
+      final ScrollBehavior onceCopiedBehavior = defaultBehavior.copyWith(
+        dragDevices: PointerDeviceKind.values.toSet(),
+      );
+      expect(onceCopiedBehavior.dragDevices, PointerDeviceKind.values.toSet());
+
+      // Copy again. The previously modified drag devices should carry over.
+      final ScrollBehavior twiceCopiedBehavior = onceCopiedBehavior.copyWith();
+      expect(twiceCopiedBehavior.dragDevices, PointerDeviceKind.values.toSet());
+    });
+
+    testWidgets('androidOverscrollIndicator', (WidgetTester tester) async {
+      // Regression test for https://github.com/flutter/flutter/issues/91673
+      const ScrollBehavior defaultBehavior = ScrollBehavior();
+      expect(defaultBehavior.androidOverscrollIndicator, AndroidOverscrollIndicator.glow);
+
+      // Use copyWith to modify androidOverscrollIndicator
+      final ScrollBehavior onceCopiedBehavior = defaultBehavior.copyWith(
+        androidOverscrollIndicator: AndroidOverscrollIndicator.stretch,
+      );
+      expect(onceCopiedBehavior.androidOverscrollIndicator, AndroidOverscrollIndicator.stretch);
+
+      // Copy again. The previously modified value should carry over.
+      final ScrollBehavior twiceCopiedBehavior = onceCopiedBehavior.copyWith();
+      expect(twiceCopiedBehavior.androidOverscrollIndicator, AndroidOverscrollIndicator.stretch);
+    });
+
+    testWidgets('physics', (WidgetTester tester) async {
+      // Regression test for https://github.com/flutter/flutter/issues/91673
+      late ScrollPhysics defaultPhysics;
+      late ScrollPhysics onceCopiedPhysics;
+      late ScrollPhysics twiceCopiedPhysics;
+
+      await tester.pumpWidget(ScrollConfiguration(
+        // Default ScrollBehavior
+        behavior: const ScrollBehavior(),
+        child: Builder(
+          builder: (BuildContext context) {
+            final ScrollBehavior defaultBehavior = ScrollConfiguration.of(context);
+            // Copy once to change physics
+            defaultPhysics = defaultBehavior.getScrollPhysics(context);
+            return ScrollConfiguration(
+              behavior: defaultBehavior.copyWith(physics: const BouncingScrollPhysics()),
+              child: Builder(
+                builder: (BuildContext context) {
+                  final ScrollBehavior onceCopiedBehavior = ScrollConfiguration.of(context);
+                  onceCopiedPhysics = onceCopiedBehavior.getScrollPhysics(context);
+                  return ScrollConfiguration(
+                    // Copy again, physics should follow
+                    behavior: onceCopiedBehavior.copyWith(),
+                    child: Builder(
+                      builder: (BuildContext context) {
+                        twiceCopiedPhysics = ScrollConfiguration.of(context).getScrollPhysics(context);
+                        return SingleChildScrollView(child: Container(height: 1000));
+                      }
+                    )
+                  );
+                }
+              )
+            );
+          }
+        ),
+      ));
+
+      expect(defaultPhysics, const ClampingScrollPhysics(parent: RangeMaintainingScrollPhysics()));
+      expect(onceCopiedPhysics, const BouncingScrollPhysics());
+      expect(twiceCopiedPhysics, const BouncingScrollPhysics());
+    });
+
+    testWidgets('platform', (WidgetTester tester) async {
+      // Regression test for https://github.com/flutter/flutter/issues/91673
+      late TargetPlatform defaultPlatform;
+      late TargetPlatform onceCopiedPlatform;
+      late TargetPlatform twiceCopiedPlatform;
+
+      await tester.pumpWidget(ScrollConfiguration(
+        // Default ScrollBehavior
+        behavior: const ScrollBehavior(),
+        child: Builder(
+            builder: (BuildContext context) {
+              final ScrollBehavior defaultBehavior = ScrollConfiguration.of(context);
+              // Copy once to change physics
+              defaultPlatform = defaultBehavior.getPlatform(context);
+              return ScrollConfiguration(
+                  behavior: defaultBehavior.copyWith(platform: TargetPlatform.fuchsia),
+                  child: Builder(
+                      builder: (BuildContext context) {
+                        final ScrollBehavior onceCopiedBehavior = ScrollConfiguration.of(context);
+                        onceCopiedPlatform = onceCopiedBehavior.getPlatform(context);
+                        return ScrollConfiguration(
+                          // Copy again, physics should follow
+                            behavior: onceCopiedBehavior.copyWith(),
+                            child: Builder(
+                                builder: (BuildContext context) {
+                                  twiceCopiedPlatform = ScrollConfiguration.of(context).getPlatform(context);
+                                  return SingleChildScrollView(child: Container(height: 1000));
+                                }
+                            )
+                        );
+                      }
+                  )
+              );
+            }
+        ),
+      ));
+
+      expect(defaultPlatform, TargetPlatform.android);
+      expect(onceCopiedPlatform, TargetPlatform.fuchsia);
+      expect(twiceCopiedPlatform, TargetPlatform.fuchsia);
+    });
+
+    Widget wrap(ScrollBehavior behavior) {
+      return Directionality(
+          textDirection: TextDirection.ltr,
+          child: MediaQuery(
+            data: const MediaQueryData(size: Size(500, 500)),
+            child: ScrollConfiguration(
+                behavior: behavior,
+                child: Builder(
+                    builder: (BuildContext context) => SingleChildScrollView(child: Container(height: 1000))
+                )
+            ),
+          )
+      );
+    }
+
+    testWidgets('scrollbar', (WidgetTester tester) async {
+      // Regression test for https://github.com/flutter/flutter/issues/91673
+      const  ScrollBehavior defaultBehavior = ScrollBehavior();
+      await tester.pumpWidget(wrap(defaultBehavior));
+      // Default adds a scrollbar
+      expect(find.byType(RawScrollbar), findsOneWidget);
+      final ScrollBehavior onceCopiedBehavior = defaultBehavior.copyWith(scrollbars: false);
+
+      await tester.pumpWidget(wrap(onceCopiedBehavior));
+      // Copy does not add scrollbar
+      expect(find.byType(RawScrollbar), findsNothing);
+      final ScrollBehavior twiceCopiedBehavior = onceCopiedBehavior.copyWith();
+
+      await tester.pumpWidget(wrap(twiceCopiedBehavior));
+      // Second copy maintains scrollbar setting
+      expect(find.byType(RawScrollbar), findsNothing);
+
+      // For default scrollbars
+    }, variant: TargetPlatformVariant.desktop());
+
+    testWidgets('overscroll', (WidgetTester tester) async {
+      // Regression test for https://github.com/flutter/flutter/issues/91673
+      const  ScrollBehavior defaultBehavior = ScrollBehavior();
+      await tester.pumpWidget(wrap(defaultBehavior));
+      // Default adds a glowing overscroll indicator
+      expect(find.byType(GlowingOverscrollIndicator), findsOneWidget);
+      final ScrollBehavior onceCopiedBehavior = defaultBehavior.copyWith(overscroll: false);
+
+      await tester.pumpWidget(wrap(onceCopiedBehavior));
+      // Copy does not add indicator
+      expect(find.byType(GlowingOverscrollIndicator), findsNothing);
+      final ScrollBehavior twiceCopiedBehavior = onceCopiedBehavior.copyWith();
+
+      await tester.pumpWidget(wrap(twiceCopiedBehavior));
+      // Second copy maintains overscroll setting
+      expect(find.byType(GlowingOverscrollIndicator), findsNothing);
+
+      // For default glowing indicator
+    }, variant: TargetPlatformVariant.only(TargetPlatform.android));
+  });
 }