Remove alternate axis assertion from StretchingOverscrollIndicator (#120734)

* remove axes assertion

* Update packages/flutter/lib/src/widgets/overscroll_indicator.dart

Author: Piinks

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

@@ -707,6 +707,11 @@ class _StretchingOverscrollIndicatorState extends State<StretchingOverscrollIndi
     if (!widget.notificationPredicate(notification)) {
       return false;
     }
+    if (notification.metrics.axis != widget.axis) {
+      // This widget is explicitly configured to one axis. If a notification
+      // from a different axis bubbles up, do nothing.
+      return false;
+    }
 
     if (notification is OverscrollNotification) {
       _lastOverscrollNotification = notification;
@@ -716,7 +721,6 @@ class _StretchingOverscrollIndicatorState extends State<StretchingOverscrollIndi
         _accepted = confirmationNotification.accepted;
       }
 
-      assert(notification.metrics.axis == widget.axis);
       if (_accepted) {
         _totalOverscroll += notification.overscroll;
 

packages/flutter/test/widgets/overscroll_stretch_indicator_test.dart

@@ -78,6 +78,65 @@ void main() {
     );
   }
 
+  testWidgets('Stretch overscroll will do nothing when axes do not match', (WidgetTester tester) async {
+    final GlobalKey box1Key = GlobalKey();
+    final GlobalKey box2Key = GlobalKey();
+    final ScrollController controller = ScrollController();
+    await tester.pumpWidget(
+      Directionality(
+        textDirection: TextDirection.ltr,
+        child: MediaQuery(
+          data: const MediaQueryData(size: Size(800.0, 600.0)),
+          child: ScrollConfiguration(
+            behavior: const ScrollBehavior().copyWith(overscroll: false),
+            child: StretchingOverscrollIndicator(
+              axisDirection: AxisDirection.right,
+              child: CustomScrollView(
+                controller: controller,
+                slivers: <Widget>[
+                  SliverToBoxAdapter(child: Container(
+                    color: const Color(0xD0FF0000),
+                    key: box1Key,
+                    height: 250.0,
+                  )),
+                  SliverToBoxAdapter(child: Container(
+                    color: const Color(0xFFFFFF00),
+                    key: box2Key,
+                    height: 250.0,
+                    width: 300.0,
+                  )),
+                ],
+              ),
+            ),
+          ),
+        ),
+      )
+    );
+
+    expect(find.byType(StretchingOverscrollIndicator), findsOneWidget);
+    expect(find.byType(GlowingOverscrollIndicator), findsNothing);
+    final RenderBox box1 = tester.renderObject(find.byKey(box1Key));
+    final RenderBox box2 = tester.renderObject(find.byKey(box2Key));
+
+    expect(controller.offset, 0.0);
+    expect(box1.localToGlobal(Offset.zero), Offset.zero);
+    expect(box2.localToGlobal(Offset.zero), const Offset(0.0, 250.0));
+
+    final TestGesture gesture = await tester.startGesture(tester.getCenter(find.byType(CustomScrollView)));
+    // Overscroll the start, no stretching occurs.
+    await gesture.moveBy(const Offset(0.0, 200.0));
+    await tester.pumpAndSettle();
+    expect(box1.localToGlobal(Offset.zero), Offset.zero);
+    expect(box2.localToGlobal(Offset.zero).dy, 250.0);
+
+    await gesture.up();
+    await tester.pumpAndSettle();
+
+    // Overscroll released
+    expect(box1.localToGlobal(Offset.zero), Offset.zero);
+    expect(box2.localToGlobal(Offset.zero), const Offset(0.0, 250.0));
+  });
+
   testWidgets('Stretch overscroll vertically', (WidgetTester tester) async {
     final GlobalKey box1Key = GlobalKey();
     final GlobalKey box2Key = GlobalKey();