cacheExtent setter regression?

main.dart

import 'package:flutter/rendering.dart';
import 'package:flutter/widgets.dart';
import 'package:flutter_test/flutter_test.dart';

void main() {
  test('RenderViewport cacheExtent setter bug reproduction', () {
    final viewport = RenderViewport(
      axisDirection: AxisDirection.down,
      crossAxisDirection: AxisDirection.right,
      offset: ViewportOffset.fixed(0.0),
    );

    // New default is viewport-based
    expect(viewport.scrollCacheExtent.style, CacheExtentStyle.viewport);

    // Using deprecated setter with a pixel value
    viewport.cacheExtent = 300.0;

    // BUG: It still thinks it's in 'viewport' style, so it's now 300 viewports.
    expect(viewport.scrollCacheExtent.style, CacheExtentStyle.viewport);
    expect(viewport.scrollCacheExtent.value, 300.0);
  });

  testWidgets('Extremely large cache extent from deprecated setter', (WidgetTester tester) async {
    final List<int> builtIndices = [];
    await tester.pumpWidget(
      Directionality(
        textDirection: TextDirection.ltr,
        child: ListView.builder(
          itemBuilder: (context, index) {
            builtIndices.add(index);
            return SizedBox(height: 100, child: Text('Item $index'));
          },
        ),
      ),
    );

    final RenderViewport renderViewport = tester.renderObject(find.byType(Viewport));
    await tester.pump();
    expect(builtIndices.length, lessThan(20));

    // REGRESSION: Using the deprecated setter.
    // A developer setting 300.0 likely expects 300 pixels of cache.
    // However, it incorrectly preserves the 'viewport' style from the new default.
    renderViewport.cacheExtent = 300.0;

    builtIndices.clear();
    await tester.pump();

    // In a 600px high viewport, 300 viewports = 1800 items!
    print('Items built with cacheExtent=300: ${builtIndices.length}');
    expect(builtIndices.length, greaterThan(1000));
  });
}