#+TITLE: ReasonML layer

#+TAGS: general|layer|multi-paradigm|programming

[[https://reasonml.github.io/img/reason.svg]]

* Table of Contents                     :TOC_5_gh:noexport:
- [[#description][Description]]
  - [[#features][Features:]]
- [[#install][Install]]
  - [[#merlin][Merlin]]
  - [[#refmt][Refmt]]
- [[#key-bindings][Key bindings]]
- [[#thanks][Thanks]]

* Description
Spacemacs layer for ReasonML, based around [[https://github.com/reasonml-editor/reason-mode][reason-mode]].

** Features:
- Syntax highlighting / indentation
- Autocomplete (via =merlin=)
- Lint / error display (via =merlin=, and =flycheck= if =syntax-checking= layer is enabled)
- REPL via =rtop=
- Auto-formatting (via =refmt=)

* Install
To use this configuration layer, add it to your =~/.spacemacs=. You will need to
add =reasonml= to the existing =dotspacemacs-configuration-layers= list in this
file.

This layer depends on the `ocaml` layer which should be installed automatically.

** Merlin
You'll need merlin (binaries =ocamlmerlin= and =ocamlmerlin-reason=) installed
on your system and on your =PATH= for errors and auto-completion.

If you're familiar with =opam= you can

#+BEGIN_SRC sh
  opam install merlin reason
#+END_SRC

to get =ocamlmerlin= and =ocamlmerlin-reason= on your current =opam= switch.

** Refmt
Similarly to Merlin, you'll need the =refmt= binary on your path.

If you're familiar with =opam= you can

#+BEGIN_SRC sh
  opam install reason
#+END_SRC

to get =refmt= in your current =opam switch=.

If your project depends on a specific version of =refmt=, you can set
=refmt-command= (via =customize-mode= or =(setq refmt-command ..)=) to the path
to a particular binary. You can also use the special values ='npm= or ='opam= to
run =refmt= via =npx= or =opam exec=, which will keep you on the correct version
for your current opam switch, or the project-local of =node_modules=.

You can toggle =refmt= on save with =SPC m r t=. To permanently enable it, add the layer variable:

#+BEGIN_SRC emacs-lisp
  (reasonml :variables reason-auto-refmt t)
#+END_SRC

in your =dotspacemacs-configuration-layers=.

* Key bindings
The main key bindings, see =packages.el= for the main list.

| Key binding   | Description                           |
|---------------+---------------------------------------|
| ~SPC m g g~   | Jump to definition                    |
| ~SPC m g G~   | Jump to definition (other window)     |
| ~SPC m g b~   | Jump back                             |
| ~SPC m h t~   | Show type                             |
| ~SPC m h h~   | Show docs                             |
| ~SPC m r d~   | Merlin destruct                       |
| ~SPC m = =~   | Refmt                                 |
| ~SPC m t r~   | Toggle auto-refmt on save             |
| ~SPC m = m r~ | Refmt: convert ml syntax to re syntax |
| ~SPC m = r m~ | Refmt: convert re syntax to ml syntax |

* Thanks
Special thanks to [[https://github.com/fredyr][fredyr]] who wrote the initial version of this layer.