Remove single axis assertion (#120738)

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

@@ -201,6 +201,11 @@ class _GlowingOverscrollIndicatorState extends State<GlowingOverscrollIndicator>
     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;
+    }
 
     // Update the paint offset with the current scroll position. This makes
     // sure that the glow effect correctly scrolls in line with the current
@@ -236,7 +241,6 @@ class _GlowingOverscrollIndicatorState extends State<GlowingOverscrollIndicator>
         }
       }
       assert(controller != null);
-      assert(notification.metrics.axis == widget.axis);
       if (_accepted[isLeading]!) {
         if (notification.velocity != 0.0) {
           assert(notification.dragDetails == null);

packages/flutter/test/widgets/overscroll_indicator_test.dart

@@ -233,6 +233,35 @@ void main() {
     expect(painter, doesNotOverscroll);
   });
 
+  testWidgets('Overscroll ignored from alternate axis', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      const Directionality(
+        textDirection: TextDirection.ltr,
+        child: ScrollConfiguration(
+          behavior: TestScrollBehaviorNoGlow(),
+          child: GlowingOverscrollIndicator(
+            axisDirection: AxisDirection.right,
+            color: Color(0xFF0000FF),
+            child: CustomScrollView(
+              physics: AlwaysScrollableScrollPhysics(),
+              slivers: <Widget>[
+                SliverToBoxAdapter(child: SizedBox(height: 20.0)),
+              ],
+            ),
+          ),
+        ),
+      ),
+    );
+    final RenderObject painter = tester.renderObject(find.byType(CustomPaint));
+    await slowDrag(tester, const Offset(200.0, 200.0), const Offset(0.0, 5.0));
+    expect(painter, doesNotOverscroll);
+    await slowDrag(tester, const Offset(200.0, 200.0), const Offset(0.0, -5.0));
+    expect(painter, doesNotOverscroll);
+
+    await tester.pumpAndSettle(const Duration(seconds: 1));
+    expect(painter, doesNotOverscroll);
+  });
+
   testWidgets('Overscroll horizontally', (WidgetTester tester) async {
     await tester.pumpWidget(
       const Directionality(
@@ -570,3 +599,12 @@ class TestScrollBehavior2 extends ScrollBehavior {
     );
   }
 }
+
+class TestScrollBehaviorNoGlow extends ScrollBehavior {
+  const TestScrollBehaviorNoGlow();
+
+  @override
+  Widget buildOverscrollIndicator(BuildContext context, Widget child, ScrollableDetails details) {
+    return child;
+  }
+}