Nested widget does not reparent children with global keys

[aikalant]

When the globally key'd children of a Nested widget vary in order or quantity between rebuilds, it looks like they are not reparented as they would if they were built manually without Nested.

Attached a flutter app demonstrating this - tap the red button a few times to induce an error:
nested_bug.zip

import 'dart:math';

import 'package:collection/collection.dart';
import 'package:flutter/widgets.dart';
import 'package:nested/nested.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return WidgetsApp(
      title: 'Nested Bug',
      color: const Color.fromARGB(255, 0, 0, 0),
      builder: (context, _) => const App(),
    );
  }
}

class App extends StatefulWidget {
  const App({super.key});

  @override
  State<App> createState() => _AppState();
}

class _AppState extends State<App> {
  static final List<GlobalKey> keys = List.generate(10, (index) => GlobalKey());
  var numNestedWidgets = 0;
  var useNested = false;

  @override
  Widget build(BuildContext context) {
    final buttons = Column(
      mainAxisAlignment: MainAxisAlignment.center,
      children: [
        GestureDetector(
          onTap: () {
            print("\x1B[2J\x1B[0;0H"); //clear console
            setState(() {
              useNested = false;
              numNestedWidgets = Random().nextInt(10);
            });
          },
          child: Container(
            width: 200,
            height: 100,
            alignment: Alignment.center,
            color: const Color.fromARGB(255, 64, 133, 46),
            child: const Text('rebuild manually'),
          ),
        ),
        Text('nested widgets: $numNestedWidgets',
            style: const TextStyle(color: Color.fromARGB(255, 0, 0, 0))),
        GestureDetector(
          onTap: () {
            print("\x1B[2J\x1B[0;0H"); //clear console
            setState(() {
              useNested = true;
              numNestedWidgets = Random().nextInt(10);
            });
          },
          child: Container(
            width: 200,
            height: 100,
            alignment: Alignment.center,
            color: const Color.fromARGB(255, 133, 46, 46),
            child: const Text('rebuild with Nested'),
          ),
        )
      ],
    );
    if (useNested) {
      print('rebuilding with $numNestedWidgets nested widgets (nested)');
      final nestedWidgets = generateNestedWidgets(context);
      return nestedWidgets.isEmpty
          ? buttons
          : Nested(children: nestedWidgets, child: buttons);
    } else {
      print('rebuilding with $numNestedWidgets nested widgets (manual)');
      return generateNestedWidget(keys.sample(numNestedWidgets), buttons);
    }
  }

  Widget generateNestedWidget(Iterable<GlobalKey> keys, Widget lastChild) {
    return keys.isEmpty
        ? lastChild
        : NestedWidget(
            key: keys.first,
            child: generateNestedWidget(keys.skip(1), lastChild),
          );
  }

  List<SingleChildWidget> generateNestedWidgets(BuildContext context) {
    return keys
        .sample(numNestedWidgets)
        .map((key) => NestedWidget(key: key))
        .toList();
  }
}

class NestedWidget extends SingleChildStatefulWidget {
  const NestedWidget({super.key, super.child});

  @override
  SingleChildState<NestedWidget> createState() => _NestedWidgetState();
}

class _NestedWidgetState extends SingleChildState<NestedWidget> {
  @override
  void initState() {
    print('nested widget state regenerated');
    super.initState();
  }

  @override
  Widget buildWithChild(BuildContext context, Widget? child) {
    return child ?? const SizedBox.shrink();
  }
}