Code completion, documentation look-up, code navigation and refactoring (merlin)
Type, documentation and function argument display on idle (merlin-eldoc)
REPL (utop)
Syntax-checking (merlin with flycheck-ocaml)
Auto-indentation (ocp-indent)
Code formatting (ocamlformat)
Dune file format (dune)

Table of Contents TOC

Module Flags

This module provides the +opam-site-lisp flag to compile editor support .el files from opam's site-lisp directory. By default all editor plugins are installed from MELPA/GitHub even if the corresponding opam package isn't installed. If this flag is enabled then you must have all of the packages listed in package.el installed via opam.

To enable this, use:

(doom! :lang (ocaml +opam-site-lisp))

Prerequisites

It is highly recommended to install opam. To get all the features you should also install these opam packages, however they are not all required (features should be disabled gracefully when a tool is missing):

opam install merlin utop ocp-indent dune ocamlformat

Features

the following files should have syntax highlighting support:

.ml{i,p,y,}, .eliom{i,}, jbuild, dune, opam

merlin-mode is activated whenever a .merlin file is found (including in a parent directory) and ocamlmerlin executable is present
line-based auto-indentation is provided by ocp-indent when installed

Configuration

if :completion company is enabled then autocomplete is provided by merlin
when :tools flycheck is enabled then flycheck-ocaml is activated to do on-the-fly syntax/type checking via merlin, otherwise this is only done when the file is saved.
spell checking is activated in comments if :tools flyspell is active
a REPL is provided if utop is installed and :feature eval is active
if :editor format is enabled, the ocamlformat executable is available and there is an .ocamlformat file present then format-all-buffer is bound to ocamlformat, otherwise to ocp-indent
if :editor multiple-cursors is enabled then identifiers can be refactored with v R and multiple cursors (this correctly matches identifier occurrences according to scope, it is not purely a textual match)
if :emacs imenu is enabled then top level symbols (modules, type, functions, etc.) can be looked up using SPC / i

Run make install to install all packages, and make doctor to diagnose missing tools.

Appendix

Commands

command	key / ex command	description
`merlin-type-enclosing`	`SPC m t`	display type under point
`tuareg-find-alternate-file`	`SPC m a`	switch between `.ml` and `.mli`
`merlin-locate`	`gd`	lookup definition
`merlin-occurences`	`SPC c D`	lookup references
`merlin-document`	`K`	lookup documentation
`merlin-imenu`	`SPC / i`	symbol lookup in file
`merlin-iedit-occurrences`	`v R`	visual refactor identifier under point (multiple cursors)
`utop`	`SPC o r`	open `utop` as REPL
`utop-eval-region`	`SPC c e`	evaluate selected region in `utop`

Hacks

set-pretty-symbols! is called with the full tuareg prettify symbol list, this can cause columns to change as certain keywords are shortened (e.g. fun becomes λ.
tuareg-opam-update-env is called the first time tuareg is loaded