Pagination approach at pub example won't dispose fetchPackagesProvider of a page even if it's out of screen

[AhmedLSayed9]

The pagination approach at pub example (Also mentioned by Remi at FlutterVikings before) won't dispose fetchPackagesProvider of a page even if it's out of screen.

i.e: If you scroll down and load second page then scroll to the top, all PackageItem of the second page will be disposed but the corresponding provider fetchPackagesProvider of that page won't be disposed.

The reason is that we're using ref of the main SearchPage widget to fetch a page:

riverpod/examples/pub/lib/search.dart

Line 86 in 4dda346

final packageList = ref.watch(

A potential solution is to wrap PackageItem with Consumer but that's not possible with declarative pagination as we need to return null to end the pagination.

Here's a minimal sample that clarifies the issue:

@riverpod
String test1(Test1Ref ref, int index) {
  ref.onDispose(() {
    print('dispose test1 at $index');
  });
  return index.toString();
}

@riverpod
String test2(Test2Ref ref, int index) {
  ref.onDispose(() {
    print('dispose test2 at $index');
  });
  return index.toString();
}

void main() {
  runApp(const ProviderScope(child: MyApp()));
}

class MyApp extends ConsumerWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    return MaterialApp(
      home: Scaffold(
        body: CustomScrollView(
          cacheExtent: 0,
          slivers: [
            SliverList(
              delegate: SliverChildBuilderDelegate(
                (context, index) {
                  ref.watch(test1Provider(index));
                  return Consumer(
                    builder: (context, ref, child) {
                      ref.watch(test2Provider(index));
                      return ListTile(title: Text(index.toString()));
                    },
                  );
                },
              ),
            ),
          ],
        ),
      ),
    );
  }
}