dune

; `dirs` is a stanza to tell dune which subfolders from the current folder
; (where the `dune` file is) it should process. Here it is saying to include
; all directories that don't start with . or _, but exclude node_modules.

(dirs :standard \ node_modules)

; `melange.emit` is a Dune stanza that will produce build rules to generate
; JavaScript files from sources using the Melange compiler
; https://dune.readthedocs.io/en/stable/melange.html#melange-emit

(melange.emit
 ; The `target` field is used by Dune to put all JavaScript artifacts in a
 ; specific folder inside `_build/default`
 (target output)
 ; Here's the list of dependencies of the stanza. In this case (being
 ; `melange.emit`), Dune will look into those dependencies and generate rules
 ; with JavaScript targets for the modules in those libraries as well.
 ; Caveat: the libraries need to be specified with `(modes melange)`.
 (libraries reason-react)
 ; The `preprocess` field lists preprocessors which transform code before it is
 ; compiled. melange.ppx allows to use Melange attributes [@mel. ...]
 ; (https://melange.re/v2.0.0/communicate-with-javascript/#attributes)
 ; reason-react-ppx allows to use JSX for ReasonReact components by using the
 ; [@JSX] attributes from Reason: https://reasonml.github.io/docs/en/jsx
 (preprocess
  (pps melange.ppx reason-react-ppx))
 ; module_systems lets you specify commonjs (the default) or es6
 (module_systems es6))