ShowCaretOnScreen is correctly scheduled within a SliverMainAxisGroup (#141671)

Fixes #141577 
Fixes #135407

Author: yiiim

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

@@ -203,6 +203,30 @@ class RenderSliverMainAxisGroup extends RenderSliver with ContainerRenderObjectM
     }
   }
 
+  @override
+  double? childScrollOffset(RenderObject child) {
+    assert(child.parent == this);
+    final GrowthDirection growthDirection = constraints.growthDirection;
+    switch (growthDirection) {
+      case GrowthDirection.forward:
+        double childScrollOffset = 0.0;
+        RenderSliver? current = childBefore(child as RenderSliver);
+        while (current != null) {
+          childScrollOffset += current.geometry!.scrollExtent;
+          current = childBefore(current);
+        }
+        return childScrollOffset;
+      case GrowthDirection.reverse:
+        double childScrollOffset = 0.0;
+        RenderSliver? current = childAfter(child as RenderSliver);
+        while (current != null) {
+          childScrollOffset -= current.geometry!.scrollExtent;
+          current = childAfter(current);
+        }
+        return childScrollOffset;
+    }
+  }
+
   @override
   double childMainAxisPosition(RenderSliver child) {
     switch (constraints.axisDirection) {
@@ -254,6 +278,15 @@ class RenderSliverMainAxisGroup extends RenderSliver with ContainerRenderObjectM
       offset += childLayoutGeometry.scrollExtent;
       maxPaintExtent += child.geometry!.maxPaintExtent;
       child = childAfter(child);
+      assert(() {
+        if (child != null && maxPaintExtent.isInfinite) {
+          throw FlutterError(
+            'Unreachable sliver found, you may have a sliver behind '
+            'a sliver with infinite extent. '
+          );
+        }
+        return true;
+      }());
     }
 
     final double totalScrollExtent = offset;

packages/flutter/test/widgets/editable_text_test.dart

@@ -17101,6 +17101,44 @@ void main() {
     await tester.pumpAndSettle();
     expect(notifyCount, equals(1));
   });
+
+  testWidgets('ShowCaretOnScreen is correctly scheduled within a SliverMainAxisGroup', (WidgetTester tester) async {
+    final ScrollController scrollController = ScrollController();
+    addTearDown(scrollController.dispose);
+    final Widget widget = MaterialApp(
+      home: Scaffold(
+        body: CustomScrollView(
+        controller: scrollController,
+        slivers: const <Widget>[
+          SliverMainAxisGroup(
+              slivers: <Widget>[
+                SliverToBoxAdapter(
+                  child: SizedBox(
+                    height: 600,
+                  ),
+                ),
+                SliverToBoxAdapter(
+                  child: SizedBox(
+                    height: 44,
+                    child: TextField(),
+                  ),
+                ),
+                SliverToBoxAdapter(
+                  child: SizedBox(
+                    height: 500,
+                  ),
+                ),
+              ],
+            )
+          ],
+        ),
+      ),
+    );
+    await tester.pumpWidget(widget);
+    await tester.showKeyboard(find.byType(EditableText));
+    await tester.pumpAndSettle();
+    expect(scrollController.offset, 75.0);
+  });
 }
 
 class UnsettableController extends TextEditingController {

packages/flutter/test/widgets/sliver_main_axis_group_test.dart

@@ -728,6 +728,23 @@ void main() {
     ) as RenderSliverMainAxisGroup;
     expect(renderGroup.geometry!.cacheExtent, 850.0);
   });
+
+  testWidgets('SliverMainAxisGroup correctly handles ensureVisible', (WidgetTester tester) async {
+    final GlobalKey key = GlobalKey();
+    await tester.pumpWidget(
+      _buildSliverMainAxisGroup(
+        viewportHeight: 300,
+        slivers: <Widget>[
+          const SliverToBoxAdapter(child: SizedBox(height: 300)),
+          SliverToBoxAdapter(child: SizedBox(key: key, height: 100)),
+          const SliverToBoxAdapter(child: SizedBox(height: 300)),
+        ]
+      )
+    );
+    Scrollable.ensureVisible(key.currentContext!);
+    await tester.pumpAndSettle();
+    expect(tester.getTopLeft(find.byKey(key)), Offset.zero);
+  });
 }
 
 Widget _buildSliverList({