Support new JSX transforms

[kitsonk]

React 17 introduced new JSX transforms and they are available in TypeScript 4.1. There are two new options for "jsx" in TypeScript:

• "react-jsx"
• "react-jsxdev"

Currently with check these should be supported without any further changes, but are unsupported in --no-check and deno bundle.

We need support from swc before integrating. Ref: swc-project/swc#1103

cc/ @kdy1

[shadowtime2000]

It seems support has been added to SWC, just wondering - what exactly is left that is blocking support for this?

[kitsonk]

A fair amount, as we need to integrate it and test it. It landed too close to 1.8 for us to do the remaining work, so it will likely be in 1.9.

[kitsonk]

I have kept kicking this down the road, but I have started this now. A couple notes so far...

• tsc "blindly" take whatever is in --jsxImportSource and appends onto it /react-runtime or /react-dev-runtime. Same behaviour with swc. This causes a bit of a problem, because we always expect specifiers to end in an extension. We can insert some "magic" based on the settings/configuration, but it means we need to add it to the dependency analysis as well, to pickup the @jsxImportSource pragmas.
• Both tsc and swc support @jsxImportSource pragmas.
• swc doesn't appear to be changing the import with react-jsxdev setting. I am not 100% sure if that is my code or not, need to investigate more.

[kdy1]

If required, I'm open to accepting a trait to override logic for determining import sources.

[kitsonk]

If required, I'm open to accepting a trait to override logic for determining import sources.

Thank you. At the moment, swc is "behaving" like I expect. Considering the behaviour is consistent between swc and tsc, it feels like it would be better to have the Deno module graph do the "magical" resolution.

[kitsonk]

Need swc-project/swc#1933 resolved, but there are other challenges beyond that (mostly how to deal with the types when using the transforms).

[kitsonk]

swc-project/swc#1933 has been fixed now... will get back to this soon-ish

[kitsonk]

Not going to be able to address this for 1.14. There are still some barriers in how we deal with resolving auto-imported specifiers.