tapCallState rxjs operator for automated CallState updates

[LcsGa]

Hi everyone,

I’d like to propose a custom RxJS operator to handle CallState updates more concisely for basic use cases. The goal is to avoid repeating the same patchState blocks everywhere.

Instead of writing this:

repository.doSomething(...).pipe(
  tap({
    subscribe: () => patchState(store, setLoading('doSomething')),
    complete: () => patchState(store, setLoaded('doSomething')),
    error: (error) => patchState(store, setError(error, 'doSomething'))
  })
)

We could simply use:

repository.doSomething(...).pipe(
  tapCallState(store, 'doSomething')
)

Here is a base implementation that handles both default and named call states (this is a starting point that could be improved in terms of typing, naming, or additional features if you have any ideas):

function tapCallState<T, State extends CallStateSlice>(
  stateSource: WritableStateSource<State>,
): MonoTypeOperatorFunction<T>;

function tapCallState<T, Collection extends string, State extends NamedCallStateSlice<Collection>>(
  stateSource: WritableStateSource<State>,
  collection: Collection,
): MonoTypeOperatorFunction<T>;

function tapCallState(stateSource: WritableStateSource<any>, collection?: string) {
  return tap({
    subscribe: () => patchState(stateSource, setLoading(collection)),
    complete: () => patchState(stateSource, setLoaded(collection)),
    error: (error) => patchState(stateSource, setError(error, collection)),
  });
}

I'm interested to hear your thoughts on this!