File Extensions in ReScript 9

[jacobp100]

Thank you for filing! Check list:

• [ ] Is it a bug? Usage questions should often be asked in the forum instead.
• [x] Concise, focused, friendly issue title & description.
• [ ] A minimal, reproducible example.
  • [ ] Ideally in OCaml syntax for now. To isolate the problem caused by either Reason or the New Syntax.
• [ ] OS and browser versions, if relevant.
• [ ] Is it already fixed in master?

In ReScript 9 using ES6, all the bs-platform now have a .mjs extension. This does mean you can run your files in node without transforming. However, doesn't work out the box for Jest and React Native (although it is possible to configure them to work). There's a little more information over on this thread.

This might be more of an issue with the tools though.

Also, as an experiment, I wanted to get my whole project to run in node natively. The only the file extension that would work and was supported in ReScript was .mjs. However, I have some of my own JS files where I need to do interop. To have these work in node too, I'd have to give them the .mjs filename too.

This has made my .gitignore pretty complicated. In one submodule, I've resorted to .mjs being ignored with _*.mjs being not ignored. In another, I've hardcoded it to certain directories. Having a .bs.mjs (or maybe .res.js) would really help out here.

There might be two separate issues, or they might end up being solved same thing.

[jacobp100]

You can see my project over on https://github.com/jacobp100/technicalc-core/tree/esm - make sure you're in the esm branch

Edit: I just got Jest to use es modules directly - which means I can fully remove babel from my project. It's still experimental in Jest, but it's so much faster.

Edit 2: I went with type: module in my package.json, and used the .js extension for my js files, and .mjs for ReScript's - it made my gitignore much easier

[bobzhang]

all the bs-platform now have a .mjs extension.

only Es6 has .mjs, the commonjs still has .js extension.

https://github.com/jacobp100/technicalc-core/tree/esm this link seems to be broken. I am a bit confused by your following comment, do you have it work for your examples including react-native?

[jacobp100]

@bobzhang Sorry - I merged it into master. It's now https://github.com/jacobp100/technicalc-core/

I bundle it and copy the bundles over to my react-native project - since I have very specific bundling requirements

[jacobp100]

Just to be clear, I fixed all my issues with config changes. I now run using ES modules in node natively, and no Babel

[bobzhang]

resolved in 9.0.1