[Feature Request] Store without a Fetcher

[fardavide]

Is your feature request related to a problem? Please describe.
I would like to be able to create a (Mutable)Store for local-only data.
The goal is to replace the Repositories with Stores; the issue comes when I can't write directly to a Store that is not Mutable, but to create a MutableStore I need an Updater and a Bookeeper

Describe the solution you'd like

val localStore: MutableStore = 
  StoreBuilder
    .from(sourceOfTruth) // no fetcher
    .build() // it returns a MutableStore, because no Fetcher is declared

Describe alternatives you've considered

• Keep repositories for local only data -> different approaches in the code-base
• Pass local data source directly to the use case -> no 🙅🏻‍♂️
• Create a LocalStore in the project, which would be a clone of Store, but with local data only -> it would be confusing, it would still behave differently from the original Store, without in-memory cache and it would need to be maintained "manually"

Additional context
none

[matt-ramotar]

Hey there @4face-studi0 - Thanks for raising!

@digitalbuddha - Thoughts on a special MutableStore without Fetcher, Updater, and Bookkeeper? MutableStore delegates to Store. On first thought I think we should not change Store to handle this, but have no concern about introducing a new special MutableStore that is effectively OfflineMutableStore.

[digitalbuddha]

Interesting idea, what functionality would this store give you that dealing directly with a source of truth would not?

[fardavide]

@digitalbuddha from the top of my experience, the main benefits I see are:

1. performance benefits, trough the built-in in-memory cache
2. API benefits, since one would already have a Store that matches the pattern used elsewhere in the project, with steam and get methods.

The second one doesn't give a strong practical benefit, but I don't like the idea of having a clone of Store built in the project.
Once you committed to framework, you committed 🙂
As now, the best solution I found for myself, is just using a Store for local/remote data and the classic Repository pattern for local-only one

[digitalbuddha]

Got it thank you for the explanation. Let me give it some thought as edge cases and breaking of the usual unidirectional flow are concerns

[matt-ramotar]

#556