Will Preact stay API compatible with React 16?

[drcmda]

We usually alias to Preact in production because of the payload savings, but now that we moved to React 16 which was officially released yesterday, preact-compat is down (for instance when returning arrays). That raises questions as to how far we can go with Fiber anyway, even if preact-compat can patch some minor things. But will it support returning arrays, numbers and strings as results, portals, and eventually async scheduling?

[developit]

Hi there! All good questions. Preact-compat has to account for all of these changes, but some of them will remain in compat and not in core. Here's a list:

• Returning Arrays from render(): yes, but this is a huge change for Preact itself. It will come, but it will take time.
• Numbers & strings: this has always been supported in Preact.
• Portals: I like the idea, but there are things like event bubbling redirection that might be unworkable within preact. We'll probably have to patch them into compat. On a personal note, I don't think the event propagation redirection piece of this holds enough value for Preact to adopt it and deviate from using browser events directly.
• Async scheduling: this will absolutely be coming to Preact itself, and we'll ship a decent scheduler enabled by-default in preact-compat once it's available.

[HillLiu]

And hydrate

https://reactjs.org/docs/react-dom.html#hydrate

[vorillaz]

Waiting for hydrate since this is a breaking change for aliasing with Next.js

[effulgentsia]

Returning Arrays from render(): yes, but this is a huge change for Preact itself. It will come, but it will take time.

Is there an issue to follow for that? #406 is closed. I don't know if it's appropriate to reopen that one or start with a new one: is there definitely agreement that it's for Preact rather than for Preact-compat?

[developit]

@effulgentsia I think most people want Array returns in preact itself, but it's also quite possible doing so would necessitate a rewrite of the diff. In terms of ongoing discussion, @tkh44 was working some magic in #703.

[vorillaz]

@developit Watching this closely as Next.js is strictly packed with React 16. Is there any chance to help you out with missing API changes?

[developit]

Yes! Jump on slack and we can work out what to do.

[alexparish]

Does anyone have a rough timeline for React 16 compatibility? Particularly interested in support for the hydrate function.