Fix crash from invalid ListWheelViewport assertion (#126539)

Fixes https://github.com/flutter/flutter/issues/126491

packages/flutter/lib/src/rendering/list_wheel_viewport.dart

@@ -1067,18 +1067,6 @@ class RenderListWheelViewport
     return result;
   }
 
-  static bool _debugAssertValidPaintTransform(ListWheelParentData parentData) {
-    if (parentData.transform == null) {
-      throw FlutterError(
-        'Child paint transform happened to be null. \n'
-        '$RenderListWheelViewport normally paints all of the children it has laid out. \n'
-        'Did you forget to update the $ListWheelParentData.transform during the paint() call? \n'
-        'If this is intetional, change or remove this assertion accordingly.'
-      );
-    }
-    return true;
-  }
-
   static bool _debugAssertValidHitTestOffsets(String context, Offset offset1, Offset offset2) {
     if (offset1 != offset2) {
       throw FlutterError("$context - hit test expected values didn't match: $offset1 != $offset2");
@@ -1090,7 +1078,6 @@ class RenderListWheelViewport
   void applyPaintTransform(RenderBox child, Matrix4 transform) {
     final ListWheelParentData parentData = child.parentData! as ListWheelParentData;
     final Matrix4? paintTransform = parentData.transform;
-    assert(_debugAssertValidPaintTransform(parentData));
     if (paintTransform != null) {
       transform.multiply(paintTransform);
     }
@@ -1110,15 +1097,13 @@ class RenderListWheelViewport
     while (child != null) {
       final ListWheelParentData childParentData = child.parentData! as ListWheelParentData;
       final Matrix4? transform = childParentData.transform;
-      assert(_debugAssertValidPaintTransform(childParentData));
+      // Skip not painted children
+      if (transform != null) {
         final bool isHit = result.addWithPaintTransform(
           transform: transform,
           position: position,
           hitTest: (BoxHitTestResult result, Offset transformed) {
             assert(() {
-            if (transform == null) {
-              return _debugAssertValidHitTestOffsets('Null transform', transformed, position);
-            }
               final Matrix4? inverted = Matrix4.tryInvert(PointerEvent.removePerspectiveTransform(transform));
               if (inverted == null) {
                 return _debugAssertValidHitTestOffsets('Null inverted transform', transformed, position);
@@ -1131,6 +1116,7 @@ class RenderListWheelViewport
         if (isHit) {
           return true;
         }
+      }
       child = childParentData.previousSibling;
     }
     return false;

packages/flutter/test/cupertino/picker_test.dart

@@ -10,6 +10,7 @@ import 'package:flutter/services.dart';
 import 'package:flutter_test/flutter_test.dart';
 
 import '../rendering/mock_canvas.dart';
+import '../rendering/rendering_tester.dart';
 
 class SpyFixedExtentScrollController extends FixedExtentScrollController {
   /// Override for test visibility only.
@@ -528,4 +529,61 @@ void main() {
     expect(controller.positions.length, 0);
   });
 
+  testWidgets('Registers taps and does not crash with certain diameterRatio', (WidgetTester tester) async {
+    // Regression test for https://github.com/flutter/flutter/issues/126491
+
+    final List<int> children = List<int>.generate(100, (int index) => index);
+    final List<int> paintedChildren = <int>[];
+    final Set<int> tappedChildren = <int>{};
+
+    await tester.pumpWidget(CupertinoApp(
+      home: Align(
+        alignment: Alignment.topLeft,
+        child: Center(
+          child: SizedBox(
+            height: 120,
+            child: CupertinoPicker(
+              itemExtent: 55,
+              diameterRatio: 0.9,
+              onSelectedItemChanged: (int index) {},
+              children: children
+                .map<Widget>((int index) =>
+                  GestureDetector(
+                    key: ValueKey<int>(index),
+                    onTap: () {
+                      tappedChildren.add(index);
+                    },
+                    child: SizedBox(
+                      width: 55,
+                      height: 55,
+                      child: CustomPaint(
+                        painter: TestCallbackPainter(onPaint: () {
+                          paintedChildren.add(index);
+                        }),
+                      ),
+                    ),
+                  ),
+                )
+                .toList(),
+            ),
+          ),
+        ),
+      ),
+    ));
+
+    // Children are painted two times for whatever reason
+    expect(paintedChildren, <int>[0, 1, 0, 1]);
+
+    // Expect hitting 0 and 1, which are painted
+    await tester.tap(find.byKey(const ValueKey<int>(0)));
+    expect(tappedChildren, const <int>[0]);
+
+    await tester.tap(find.byKey(const ValueKey<int>(1)));
+    expect(tappedChildren, const <int>[0, 1]);
+
+    // The third child is not painted, so is not hit
+    await tester.tap(find.byKey(const ValueKey<int>(2)), warnIfMissed: false);
+    expect(tappedChildren, const <int>[0, 1]);
+  });
+
 }

packages/flutter/test/widgets/list_wheel_scroll_view_test.dart

@@ -1642,6 +1642,65 @@ void main() {
 
       expect(pageController.page, 1.0);
     });
+
+    testWidgets('ListWheelScrollView does not crash and does not allow taps on children that were laid out, but not painted', (WidgetTester tester) async {
+      // Regression test for https://github.com/flutter/flutter/issues/12649
+
+      final FixedExtentScrollController controller = FixedExtentScrollController();
+      final List<int> children = List<int>.generate(100, (int index) => index);
+      final List<int> paintedChildren = <int>[];
+      final Set<int> tappedChildren = <int>{};
+
+      await tester.pumpWidget(
+        Directionality(
+          textDirection: TextDirection.ltr,
+          child: Center(
+            child: SizedBox(
+              height: 120,
+              child: ListWheelScrollView.useDelegate(
+                controller: controller,
+                physics: const FixedExtentScrollPhysics(),
+                diameterRatio: 0.9,
+                itemExtent: 55,
+                squeeze: 1.45,
+                childDelegate: ListWheelChildListDelegate(
+                  children: children
+                    .map((int index) => GestureDetector(
+                      key: ValueKey<int>(index),
+                      onTap: () {
+                        tappedChildren.add(index);
+                      },
+                      child: SizedBox(
+                        width: 55,
+                        height: 55,
+                        child: CustomPaint(
+                          painter: TestCallbackPainter(onPaint: () {
+                            paintedChildren.add(index);
+                          }),
+                        ),
+                      ),
+                    ))
+                    .toList(),
+                ),
+              ),
+            ),
+          ),
+        ),
+      );
+
+      expect(paintedChildren, <int>[0, 1]);
+
+      // Expect hitting 0 and 1, which are painted
+      await tester.tap(find.byKey(const ValueKey<int>(0)));
+      expect(tappedChildren, const <int>[0]);
+
+      await tester.tap(find.byKey(const ValueKey<int>(1)));
+      expect(tappedChildren, const <int>[0, 1]);
+
+      // The third child is not painted, so is not hit
+      await tester.tap(find.byKey(const ValueKey<int>(2)), warnIfMissed: false);
+      expect(tappedChildren, const <int>[0, 1]);
+    });
   });
 
   testWidgets('ListWheelScrollView creates only one opacity layer for all children', (WidgetTester tester) async {