Transpilation

[rtsao]

As of now, FastpackTranspiler supports a few, mostly non-standard syntax features (JSX, decorators) and some stage 3 features (spread).

What is the goal of this project in terms of transpilation? Some things like async/await to promises might be useful. Is a full-blown ES2015 to ES5 transpilation out of scope?

If fastpack supported something akin to babel-preset-env (where the language features are transpiled based on target runtimes) that would be awesome.

[thangngoc89]

AFAIK, this project uses Flow parser so it understands any valid Flow code.

[andreypopp]

Hi, we are open for PRs to add more transpilation features to fastpack. We have infra in place for adding more transpilers and tests for them. If you are interested — definitely contribute!

The reason we didn't do it yet is just lack of time. So help is greatly appreciated.

Writing AST transform in OCaml/Reason is a pleasure — for example this is React JSX transpiler — https://github.com/fastpack/fastpack/blob/master/FastpackTranspiler/ReactJSX.ml

[zindel]

@rtsao are there any specific missing important tranpilers in your opinion? We've purposely kept the list short for the beginning in order to only support development in the latest Chrome/FF.

[rtsao]

That's what I was wondering; the set of currently implemented transforms makes sense for modern targets, but I was curious about your amenability to the adding of babel-preset-env feature parity (i.e. transpilation all the way down to ES5, depending on target).

Obviously this would be a rather large undertaking (I'd be interested in helping build this), but it would allow for more-or-less drop-in replacement for Webpack/Babel and open up the possibility of an entirely native build/compile pipeline.

[zindel]

@rtsao ok. That's definitely in the mid-term plan. In the short term we could add the config placeholder and prioritise targets/transpilers to support first

[andreypopp]

Also to mention that in the meantime we are going to rely on babel for prod builds:

fpack src/index.js \
  --output build/js \
  --transpile '^src' \
  --postprocess 'babel --presets es2015' \
  --postprocess 'uglifyjs -cm'