Use new Context API in React 16.3

[timdorr]

Re: facebook/react#11818 and reactjs/rfcs#2 (<- Warning: super long PR)

There's a new render prop/children-as-function API for context coming in the next React minor release. The big thing that's relevant to us: It works across shouldComponentUpdate boundaries without the need for subscriptions. So, no more need for the blocked updates guide. Huzzah!

It will require some refactoring. And backwards compat is going to be...interesting. We may have to bump to 5.0.0 to make it clean. FWIW, React Redux is considering this too, so we're not alone. (The whole major version/breaking changes debate is probably going to fire up again 🙄 )

I'm going to start tooling around with it over the weekend. The fun bit: turning on this and async rendering at the same time 😲

[brianespinosa]

This is the best news I've heard all week.

[pshrmn]

Handling backwards compatibility is the big issue for me. I half feel like there will need to be two versions of components (<Link> & <LegacyLink>?) until the old context can safely be removed, but I haven't wrapped my head around what will be required yet.

[timdorr]

It's pretty easy to do feature detection:

if (React.createContext) {
  // new hotness
} else {
  // old and busted
}

It's just a matter of how different the refactor would be and how much that would bloat the bundle size.

[odiseo42]

My prayers have been answered! \o/

[Inucoder]

I'm very happy about the update blocking issue getting finally fixed! It's really a pain to deal with when working with libraries like react-redux or your own shouldComponentUpdate implementations on large projects. I have spent several hours working around the problem and my guess was you guys were going to solve it for the next major release!

[pshrmn]

Edit no. 2: I think I just misunderstood this before. I'm reading the tests now and nesting is supported. 😅

[Inucoder]

@timdorr, do you have an ETA for when this update might make it to a release? That would help our team plan ahead because we have a few React Router related tasks in schedule that would not make sense to execute if this nice fix gets released. Regards, keep the great work.

[pshrmn]

@Inucoder You can watch #5908 but there isn't really a schedule and it is more dependent on React releases. React 16.3 should be released in a few weeks, so that is the first time anyone can easily test the new context API out, and even then it will be "unstable". React 17 should be when the stable context API is released, which is on the order of months.

[hilkeheremans]

A potential, but probably not ideal alternative for backwards compatibility is to polyfill when needed:
https://github.com/thejameskyle/create-react-context

Not actively suggested this as I haven't tested this, just throwing it out there as an option.

[timdorr]

@hilkeheremans Yes, I'm doing that in #5908

[corysimmons]

@hilkeheremans Seems to work fairly seamlessly https://codesandbox.io/s/1vnnrmnv4

[sshmyg]

What about new context API for react-router 3?