Allow React support to be optional

It would be nice if React support was optional, such that if you didn’t want to use it, the dependencies aren’t downloaded. Currently, the entire React library is imported whether or not you want to use it, which might not be ideal for something like a pure API.

It could be done by allowing React to be added in manually by importing something like react.ts (which would be next to main.ts) and using its exports, or by allowing React to be imported by the consumer and then provided to the API (this would allow users to select a specific version of React as well, or maybe even be able to use Preact).

I’m not sure on the best way to implement it, but if this is something worth looking into, I’d be happy to try and write up a PR!

[luvies]

I’m going to open an issue for middleware since it seems a bit out of scope for this issue (and I wanted to suggest a possible API for it)

[sholladay]

Having thought about this for a few days, here’s what I’ve decided:

1. React support will remain built-in. It’s a selling point and I personally use it a lot. Deno renders JSX out-of-the-box, and most backend projects will need a view engine of some sort, so we might as well leverage it.
2. The user ought to have some control over the React version used by the framework, somewhat akin to Node’s peerDependencies. For that, I will accept a PR that adds a react server option, which can be used to override the built-in version that ships with the framework. However, I would encourage users to use an import map instead, so that only one React is ever downloaded. PR welcome for documenting how to do that.

I’m happy to revisit this approach in the future. In particular, if Deno’s tooling around peer dependencies improves, that may open up new opportunities for us.