Edit

Editor Setup

Merlin is the tool used for code completion, type querying, locating definitions etc for OCaml. Regardless of which editor you use, you’ll want to install Merlin for your ocaml compiler with opam install merlin.

Visual Studio Code

This is the easiest editor to set up for OCaml. Just install the OCaml and Reason IDE extension:

code --install-extension freebroccolo.reasonml

Vim or Neovim

Vim and Neovim are relatively complex tools, and their configuration requires editing their .vimrc file (in the case of Neovim, it’s .config/nvim/init.vim on Linux).

Merlin Plugin

In order to just have basic Merlin support, all you need is to add this snippet to enable Merlin’s VIM plugin:

if executable('opam')
  let g:opamshare=substitute(system('opam config var share'),'\n$','','''')
  if isdirectory(g:opamshare."/merlin/vim")
    execute "set rtp+=" . g:opamshare."/merlin/vim"
  endif
endif

This approach has the advantage of loading the same plugin version as is available in Merlin via OPAM, preventing any mismatches.

Use :help merlin to find out the keybindings. A completion engine, like Ale, is recommended as well.

emacs

Install tooling libraries and the user-setup assitant with

opam install user-setup merlin tuareg ocamlformat ocp-indent

Then run the user-setup installation

opam user-setup install