Proposal: native compat library for syncing with server-reason-react

[jchavarri]

As server-reason-react is mirroring the API of reason-react, it becomes challenging to keep up over there with the changes done here.

We also don't want to remove the external declarations used on react.rei for performance reasons.

So the solution is to create a second react.rei that is used purely for syncing purposes with server-reason-react, until we have virtual libraries or better support for this. See companion PR ml-in-barcelona/server-reason-react#82.

[jchavarri]

Building this library guarantees that the contract implemented in React.re is fitting the one used in server-reason-react.

Once there are breaking changes, the process will be as follows:

• build of unused_native_compat will fail because contract is not honored anymore
• update React.rei here to reflect new contract until build passes
• copy React.rei over to server-reason-react
• proceed to update implementation in server-reason-react to fulfill new contract

[jchavarri]

Talked to @davesnx offline and we decided to explore a different path, where we use server-reason-react.melange.ppx which is already removing the differences between melange and native, to process react.rei and convert externals into regular let definitions, e.g.

[@mel.module "react"]
external useMemo: ([@mel.uncurry] (unit => 'any)) => 'any = "useMemo";

into

let useMemo: (unit => 'any) => 'any;

That way, we might be able to start working towards a reason-react virtual library that includes the mli "as is" currently.