[Bug]: RemoteState.Guard will return success for a null value in release mode and error in debug mode

[chadrickman]

Describe the bug
If you pass a future to RemoteState.Guard that returns a null value, in release mode it'll go through as a success but in debug mode the assert that the value can't be null will be prevent it and an error state is returned.

Expected behavior
An error state should be returned for for both instances or a different state might need to be addressed.

Screenshots
N/A

Smartphone (please complete the following information):

• No device specific

[chimon2000]

@chadrickman that assertion sounds like it is happening inside the dart language. Also, is null a valid value?

[chimon2000]

@chadrickman thinking about it further, I'm not sure if this is a bug so much as it is just not conveying that the return type could be nullable.

Pretending that there is a future that can return an int or null

  Future<RemoteState<int>> getCount() async {
    RemoteState<int> state = RemoteState.loading();

    state = await RemoteState.guard(() => _counterClient.getCount());

    return state;
  }

In this case, if _counterClient.getCount() can return null then it is probably better to change the function to forward the nullable value or to handle the null scenario explicitly.

  Future<RemoteState<int>> getCount() async {
    RemoteState<int> state = RemoteState.loading();

    /// getCount returns Future<int?> forcing us to handle null.
    state = await RemoteState.guard(
        () => _counterClient.getCount().then((count) => count ?? 0));

    return state;
  }

/// Example where we forward null up.
  Future<RemoteState<int?>> getCount() async {
    RemoteState<int?> state = RemoteState.loading();

    /// getCount returns Future<int?> so we just forward null up the chain.
    state = await RemoteState.guard(
        () => _counterClient.getCount());

    return state;
  }