main.dart

// .then block does not complete
Future<void> foo_then_bad() async {
  final future = Future(() => print('foo_then_bad: started'))
    .then((_) async => () async {
      await Future.delayed(Duration(seconds: 1), null);
      print('foo_then_bad: 111');
      await Future.delayed(Duration(seconds: 1), null);
      print('foo_then_bad: 222');
    });  
  
  return await future;
}

// .then block completes
Future<void> foo_then_good() async {
  final future = Future(() => print('foo_then_good: started'))
    .then((_) async {
      await Future.delayed(Duration(seconds: 1), null);
      print('foo_then_good: 111');
      await Future.delayed(Duration(seconds: 1), null);
      print('foo_then_good: 222');
    });  
  
  return await future;
}

// full async version, for reference
Future<void> foo_async() async {
  final future = Future(() => print('foo_async: started'));
  await future;
    
  await Future.delayed(Duration(seconds: 1), null);
  print('foo_async: 111');
  await Future.delayed(Duration(seconds: 1), null);
  print('foo_async: 222');
}


void main() async {
  // Uncomment to test different versions.
  await foo_then_bad();
  await foo_then_good();
  await foo_async();
}