Deriving subscribed behaviour from Context or event emitter

[oblador]

I was really happy to see subscribed option being merged which helps a lot for react-native use cases – thanks a bunch!

I've been starting to implement it in my fairly large and complex app. It's fine to do on a few select hooks, but applying it to all is both quite cumbersome and cause a lot of unnecessary re-renders for my recently unfocused screen (which is the opposite of what I'm trying to achieve).

Looking at Legend State, they are using a context provider with an imperative API, which is precisely what I want to make it maximally performant. Would you be up for something like this? Happy to send a PR 👍

[oblador]

Before I start working on this, @TkDodo will you accept such a PR?

[TkDodo]

can you elaborate how this would be better?

[oblador]

A few:

• Not having to change third party hooks (primarily internal but also external) that use RQ but that don't expose all options
• Greatly simplified implementation in apps – I don't have to rewrite every component to use a selector for focus/subscribed, instead I can either solve it at the query/hook level, or even better at the screen level
• No unnecessary re-renders when screen focus changed, but RQ didn't

[TkDodo]

No unnecessary re-renders when screen focus changed, but RQ didn't

I don’t think that’s true because if we have a react context under the hood that’s subscribed to the boolean value, all query consumers would re-render when that focus value changes, no ?

[oblador]

The key here is with an imperative API, so in the linked example you call a method to toggle it, not settings state to re-render with a new provider value. Instead you'll subscribe to changes via an event emitter or something like that, alternatively call a getter when you need to decide whether to act on a change or not.

[TkDodo]

sorry, this proposal is too abstract for me. you mentioned context provider yourself so that’s why I thought you mean react context?

anyways, if you want to make a PR, please do so. I cannot decide upfront if I will merge it though, as I need to see it to understand it I guess ...