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https://github.com/reasonml-editor/reason-mode

Emacs major mode for working with ReasonML
https://github.com/reasonml-editor/reason-mode

emacs ocaml reasonml

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Emacs major mode for working with ReasonML

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# reason-mode

![Build Status](https://travis-ci.org/reasonml-editor/reason-mode.svg?branch=master)



An Emacs major mode for [ReasonML](https://reasonml.github.io/).



## Installation



### Prerequisites



**Note**: the following setup assumes Reason and Merlin are installed. This can be achieved by installing them from OPAM (`opam install reason merlin`). 



If you are using bucklescript, make sure you are using a compatible OCaml version (you can find the version of ocaml compatible with your bucklescript installation by running `npm bsc -version`).

At the time of writing this documentation, install OCaml 4.06.1 (for bucklescript 7.\*)



**Please verify your installation**:



```sh

ocamlc -version # 4.06.1 if you are using bucklescript

which ocamlmerlin # a valid path to the ocamlmerlin binary, mandatorily

which ocamlmerlin-reason # a valid path to the ocamlmerlin-reason binary, mandatorily

```



### MELPA



If your Emacs has `package.el` (which is automatically the case for Emacs >= 24), you can install `reason-mode` from the package in [MELPA](https://melpa.org/#/getting-started).



### QUELPA

Alternatively, you can use [quelpa](https://github.com/quelpa/quelpa) and the following recipe:



```lisp

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

```



### Manual Installation



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`:



```lisp

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

```



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



```elisp

;;----------------------------------------------------------------------------

;; 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:



```lisp

(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](https://gist.github.com/sgrove/c9bdfed77f4da8db108dfb2c188f7baf))



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



### Project specific version of `refmt`



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):



```lisp

;; can also be set via M-x `customize-mode`

(setq refmt-command 'npm)

```



### Utop



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](https://github.com/diml/utop#integration-with-emacs). Make sure it is latest `master` because the feature is fairly new.



Then in your Emacs init file add:



```lisp

(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.



### Spacemacs



The [`reasonml`](https://develop.spacemacs.org/layers/+lang/reasonml/README.html) layer is available in the develop version of spacemacs.



For the stable version of spacemacs, you can install the `reason-mode` package automatically.



```lisp

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](#manual-installation) to your `dotspacemacs/user-config`.



### Features



#### Auto-format before saving



If you have refmt installed, you can add this to your `.emacs` file to enable

auto-format:



```lisp

(add-hook 'reason-mode-hook (lambda ()

          (add-hook 'before-save-hook #'refmt-before-save)))

```



### Tests via Cask + ERT



The `test` folder contains tests that can be run via [Cask](https://github.com/cask/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.



## License



`reason-mode` is distributed under the terms of both the MIT license and the

Apache License (Version 2.0).



See [LICENSE-MIT](LICENSE-MIT) and [LICENSE-APACHE](LICENSE-APACHE) for details.