Make ViewStore.yield(while:) main actor.

[mbrandonw]

Considering that viewStore.send(_:while:) is @MainActor, it seems this one should be too.

[jshier]

I'm not sure this follows logically. While send(_:while:) is on main since it's primary use is to handle loading, yield(while:) seems like a sort of primitive that could be used for any conditional wait, including those off main. Unless, is this a move towards bringing reducers entirely onto main?

[stephencelis]

@jshier Because the condition is derived from state that lives on the main actor, we think it's important that it runs here as well.

We've also already had to push this direction for any reducers that use async effects, and we also deprecated Store.unchecked awhile ago.

We'll be able to revisit more aspects of the task/threading model in the future when we can abandon the rest of our pre-concurrency thread model, and should eventually get back to a space where we can better support both Swift concurrency and non-main reducers/stores, but weren't able to maintain both during these current, migratory moments.

[stephencelis]

Nice! I think this was just an oversight and we probably should have added it when it first shipped.

[jshier]

We'll be able to revisit more aspects of the task/threading model in the future when we can abandon the rest of our pre-concurrency thread model, and should eventually get back to a space where we can better support both Swift concurrency and non-main reducers/stores, but weren't able to maintain both during these current, migratory moments.

Ah, makes sense. Non-main reducers will likely become more important as things continue to scale.