createRef API like React 16.3

[LPGhatguy]

React 16.3+ exposes a new ref API that's intended to be the default instead of the callback refs that both React and Roact have.

I've found that a lot of users new to the React model try to do things like call setState inside refs, or do all sorts of trickery inside of them, when they really should be doing those things in didMount instead.

Switching the recommended API to a createRef-like API would prevent these issues in the future.

[AmaranthineCodices]

This would work way better than function-based refs. I am skeptical about one of the details of this:

When the ref attribute is used on a custom class component, the ref object receives the mounted instance of the component as its current.

This doesn't feel right. It's nice to completely encapsulate component behavior, and this breaks the encapsulation. With this functionality, I can write code that only works when a component is stateful, and mess with its internals arbitrarily. This is not ideal - it feels really imperative, as opposed to the general declarative nature of Roact and React.

[LPGhatguy]

I didn't even notice that, that's pretty sketchy.

We can ignore that feature for now, and if we end up really (really really) wanting that, we can add it later.

[AmaranthineCodices]

I'm working on this locally; should have something tomorrow or Wednesday.