"de-opting to synchronous mode" in use-subscription README

[jamesknelson]

Do you want to request a feature or report a bug?

Outdated README (maybe?)

What do the docs currently say?

use-subscription is safe to use in concurrent mode. However, it achieves correctness by sometimes de-opting to synchronous mode, obviating the benefits of concurrent rendering.

In the linked issue, @bvaughn explains that this is referring to chains of synchronous updates using componentDidUpdate. However, the useSubscription hook now uses a passive useEffect(), as opposed to a synchronous componentDidUpdate().

Would this mean that it's no longer "de-opting to sync mode", and the warning could be removed from the README?

[stale]

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[jamesknelson]

Would still love an answer on this one!

[bvaughn]

The wording of the README isn't super accurate for useSubscription. I kind of copy-pasted that READ (with some tweaks) from createSubscription.

That being said, useSubscription() still has some downsides (both deopts and potential tearing). The decision to use a passive effect instead of an active one was a tradeoff between lesser bad options essentially.

I took the time this afternoon to create a Gist outlining the de-opt and potential tearing cases for useSubscription and a new hook (not yet created but soon to be RFCed) called useMutableSource:
https://gist.github.com/bvaughn/054b82781bec875345bd85a5b1344698

If you'd like to send a PR to update the wording on the use-subscription README, tag me as a reviewer. Else I will do a pass eventually when I get to implementing this new hook.

[dai-shi]

#15317 (comment)
@kitten Have you seen this issue?