ReScript / NextJS Starter

This is a NextJS based template with following setup:

• Full Tailwind v2 config & basic css scaffold (+ production setup w/ purge-css & cssnano)
• ReScript + React
• Some ReScript Bindings for Next to get you started
• Preconfigured Dependencies: @rescript/react

Note: This setup is based on the v1 package-lock format utilized by npm@6. If you want to use the newer v2 version, delete the package-lock.json file and install the dependencies with npm@7.

Development

Run ReScript in dev mode:

npm run res:start

In another tab, run the Next dev server:

npm run dev

Useful commands

Build CSS seperately via postcss (useful for debugging)

# Devmode
npx postcss styles/main.css -o test.css

# Production
NODE_ENV=production npx postcss styles/main.css -o test.css

Test production setup with Next

# Make sure to uncomment the `target` attribute in `now.json` first, before you run this:
npm run build
PORT=3001 npm start

Tips

ES6 vs CommonJS

This template is complying to the ES6 module format, and therefore compiles ReScript code to mjs files. In case you want to use this template with the old commonjs format, do the following changes:

1. Set package-specs and suffix to the following configuration:

{
  //...
  "package-specs": {
    "module": "commonjs",
    "in-source": true
  },
  "suffix": ".bs.js",
}

2. Replace all import paths in pages that refer to src/MyResFile.mjs to src/MyResFile.bs.js

// pages/_app.js
+import ResApp from "src/App.mjs"
+import ResApp from "src/App.bs.js"

Done. You are now running on commonjs modules.

Don't be afraid to adapt your Next bindings

We ship some general bindings for NextJS, but we try to keep them simple. Some use-cases and APIs might not be reflected yet, so feel free to adapt the file as you see fit for your app.

As with every file fork, if you keep the changes git trackable, it's pretty straight-forward to pull in upstream changes later on.

Fast Refresh & ReScript

Make sure to create interface files (.resi) for each page/*.res file.

Fast Refresh requires you to only export React components, and it's easy to unintenionally export other values that will disable Fast Refresh (you will see a message in the browser console whenever this happens).

For the 100% "always-works-method", we recommend putting your ReScript components in e.g. the src directory, and re-export them in plain pages/*.js files instead (check out the templates initial pages directory to see how we forward our React components to make sure we fulfill the Fast-Refresh naming conventions).

Filenames with special characters

ReScript supports filenames with special characters: e.g. pages/blog/[slug].res, but be aware that you can't access these these modules within other modules (since there is no syntax to express modules with e.g. [ characters). Also don't forget to create an additional .resi file to comply to Fast Refresh rules.

Q & A

Why are the generated .mjs files tracked in git?

In ReScript, it's a good habit to keep track of the actual JS output the compiler emits. It allows quick sanity checking if we made any changes that actually have an impact on the resulting JS code (especially when doing major compiler upgrades, it's a good way to verify if production code will behave the same way as before the upgrade).

This will also make it easier for your Non-ReScript coworkers to read and understand the changes in Github PRs, and call you out when you are writing inefficient code.

If you want to opt-out, feel free to remove all compiled .mjs files within the src directory and add src/**/*.mjs in your .gitignore.

How trustworthy is this template?

This template was created through our learnings of building the ReScript Documentation Platform (which is built in NextJS), and is maintained by one of the ReScript core team members. It irregularly receives updates depending on demand and urgency (e.g. important changes in the Next.res bindings, or package dependencies).