[bug] Race condition on `write` and `read`.

[PROGrand]

Problem

Race condition on write and read.

There is FlutterSecureStorage operations async bug:

Future<void> main() async {
  WidgetsFlutterBinding.ensureInitialized();
  const storage = FlutterSecureStorage();
  await storage.write(key: 'key', value: 'value');
  assert(await storage.read(key: 'key') == 'value'); // assertion: platform [read] finishes before platform implementation [write].
}

[Daniel-Cong]

This is a feature / good thing, not a bug. By making it synchronous by default, we can go back to responding to user, while the write operation is continuing in the background. Also you can always add await on your own code if you want it to be blocking. Why are you reading said value right away anyway after writing it? I have never met such scenario in my time writing flutter app.

[hantrungkien]

@Daniel-Cong what do you think about this case:

1. When user want to logout

  Future<void> logout() async {
    await _secureStorage.delete(key: _isLoggedInKey);
    _isLoggedInSubject.add(false);
  }

2. _isLoggedInSubject will notify to GoRouter.refreshListenable to invoke GoRouter.redirect

3. In GoRouter.redirect need to directly call _secureStorage.read to determine logged in or not. However, the result from the read function may be true even though it was deleted in step 1. This causes the router to not redirect as expected.

redirect: (context, state) async {
      final path = state.uri.path;
      final isLoggedIn = (await _secureStorage.read(key: _isLoggedInKey)) != null; // for example
      if (isLoggedIn) {

      } else {

      }
    },