An Emacs major mode for ReasonML.

If your Emacs has package.el (which is automatically the case for Emacs >= 24), you can install reason-mode from the package in MELPA.

Alternatively, you can use quelpa and the following recipe:

(quelpa '(reason-mode :repo "reasonml-editor/reason-mode" :fetcher github :stable t))

Download reason-indent.el, reason-interaction.el, reason-mode.el and refmt.el at the root of this repository and place it in a vendor file next to your Emacs configuration files. Then place the following somewhere in your .emacs.el:

(add-to-list 'load-path "/path/to/vendor")

Note: the following setup assumes Reason and Merlin are installed. This can be achieved by by installing them from OPAM (opam install reason.1.13.7 merlin.2.5.4). Make sure you're on ocaml 4.02.3!

Please verify your installation:

ocamlc -version # 4.02.3
which ocamlmerlin # a valid path to the ocamlmerlin binary, mandatorily

Add the following to your ~/.emacs or ~/.emacs.d/init.el file:

;;----------------------------------------------------------------------------
;; Reason setup
;;----------------------------------------------------------------------------

(defun shell-cmd (cmd)
  "Returns the stdout output of a shell command or nil if the command returned
   an error"
  (car (ignore-errors (apply 'process-lines (split-string cmd)))))

(defun reason-cmd-where (cmd)
  (let ((where (shell-cmd cmd)))
    (if (not (string-equal "unknown flag ----where" where))
      where)))

(let* ((refmt-bin (or (reason-cmd-where "refmt ----where")
                      (shell-cmd "which refmt")
                      (shell-cmd "which bsrefmt")))
       (merlin-bin (or (reason-cmd-where "ocamlmerlin ----where")
                       (shell-cmd "which ocamlmerlin")))
       (merlin-base-dir (when merlin-bin
                          (replace-regexp-in-string "bin/ocamlmerlin$" "" merlin-bin))))
  ;; Add merlin.el to the emacs load path and tell emacs where to find ocamlmerlin
  (when merlin-bin
    (add-to-list 'load-path (concat merlin-base-dir "share/emacs/site-lisp/"))
    (setq merlin-command merlin-bin))

  (when refmt-bin
    (setq refmt-command refmt-bin)))

(require 'reason-mode)
(require 'merlin)
(add-hook 'reason-mode-hook (lambda ()
                              (add-hook 'before-save-hook 'refmt-before-save)
                              (merlin-mode)))

(setq merlin-ac-setup t)

If you have iedit mode set up:

(require 'merlin-iedit)
(defun evil-custom-merlin-iedit ()
  (interactive)
  (if iedit-mode (iedit-mode)
    (merlin-iedit-occurrences)))
(define-key merlin-mode-map (kbd "C-c C-e") 'evil-custom-merlin-iedit)

(Thanks @sgrove: https://gist.github.com/sgrove/c9bdfed77f4da8db108dfb2c188f7baf)

This associates reason-mode with .re and .rei files. To enable it explicitly, do M-x reason-mode.

If you're using different versions of refmt between projects, you can use the project-specific installed version via the special config values:

• 'npm (calls npx refmt ... to use the version of refmt installed in the project's node_modules)
• 'opam (calls opam exec -- refmt ... to use the version of refmt on the current opam switch):

;; can also be set via M-x `customize-mode`
(setq refmt-command 'npm)

Reason-mode provides (opt-in) rtop support. At the moment only the native workflow is supported.

First of all you need to install the Utop Emacs integration. Make sure it is latest master because the feature is fairly new.

Then in your Emacs init file add:

(require 'utop)
(setq utop-command "opam config exec -- rtop -emacs")
(add-hook 'reason-mode-hook #'utop-minor-mode) ;; can be included in the hook above as well

After this, the function utop (C-c C-s) will start rtop in Reason buffers.

There is currently no official reason layer available, but you can install the reason-mode package automatically. Some are working on a layer in the meantime #1149.

dotspacemacs-additional-packages
  '(
    (reason-mode
      :location (recipe
        :repo "reasonml-editor/reason-mode"
        :fetcher github
        :files ("reason-mode.el" "refmt.el" "reason-indent.el" "reason-interaction.el")))
)

Afterwards add the snippet to your dotspacemacs/user-config.

If you have refmt installed, you can add this to your .emacs file to enable auto-format:

(add-hook 'reason-mode-hook (lambda ()
          (add-hook 'before-save-hook #'refmt-before-save)))

The test folder contains tests that can be run via Cask. Once you install cask, if it is the first time run:

cask install
cask exec ./run_tests.sh

If it is not the first time you can omit the first line and execute the tests with the second one only. The environment variable EMACS controls the program that runs emacs.

reason-mode is distributed under the terms of both the MIT license and the Apache License (Version 2.0).

See LICENSE-MIT and LICENSE-APACHE for details.