React 19 & concurrent rendering

[tom-sherman]

It's a very ambitious title, I know...

The goal is to support latest canaries and concurrent rendering. If we ever get as far as this being working, it'll need to land in a new major version of ink and it'll be blocked by React 19 (unless we wanna publish an ink version that depends on a react canary version).

I think this also unlocks a more responsive Ink. Spun that out into a separate discussion here: #657

[tom-sherman]

I have a way forward with the tests. It involves wrapping rendering in act(), unmounting all instances at the end of tests, and moving some tests to async.

[tom-sherman]

@vadimdemedes @sindresorhus refactoring all of the tests is going to take substantial effort and I'm aware that there's no specific issue for this work. I just wanted to check in with you as to whether this change is something you're in favour of before I invest time into refactoring the tests.

I think this is going to see pretty much every test touched, and so definitely requires some consensus and coordination.

[tom-sherman]

It would also be good to match the react-dom and react-three-fiber APIs of createRoot(container).render(). This would allow simplifying the API a bit eg. No need for options to be a NodeJS.WriteStream | RenderOptions union anymore as the stream would be passed into the container. We can also get rid of the instances WeakMap this way.

To summarise my proposal:

const root = createRoot({ stdout, stdin });
root.render(<App />);`

[sindresorhus]

I think this is a good idea in general, but the final decision is up to @vadimdemedes.

[sindresorhus]

I think it also may be a bit too early. We cannot merge this until React 19 is out as otherwise we are not able to do new releases, and if this stays open for a long time with so many tests changes, it will be prone to lots of merge conflicts.

[tom-sherman]

That's a good point, I wonder if there is a different way forward.

For example a new createRoot API could be shipped in a minor version (or @next tag) that uses a vendored React canary version - Next.js does this.

I think there's lots of value around allowing users (particularly library authors) to opt into this change before React 19 is released.