Vim / NeoVim

Setup using Coc

The following instructions should enable Erlang language server integration via the Coc system (an intellisense engine for both Vim and Neovim).

Installing Coc with vim-plug

For vim-plug users with nodejs >= 10.12 installed, installing the plugin is just:

" Use release branch (Recommended)
Plug 'neoclide/coc.nvim', {'branch': 'release'}

To make the plugin aware of erlang_ls however, it needs configuration.

Coc plugin configuration

Coc is configured through coc-settings.json, which can be opened in vim by issuing the command:

:CocConfig

If erlang_ls is present in your $PATH variable then the following config should suffice:

{
  "languageserver": {
    "erlang": {
      "command": "erlang_ls",
      "filetypes": ["erlang"]
    }
  }
}

When vim starts editing a file of filetype erlang, if the erlang_ls server can be started and connected to, you should see something like the following message from Coc:

[coc.nvim] Erlang LS (in erlang_ls), version: X.Y.Z+build.REF

For suggestions on configuring Coc and possible key-bindings see its example configuration documentation.

Setup for Neovim using the built-in language server client

The following instructions should enable Erlang language server integration using the built-in language server client in Neovim. The nvim-lspconfig plugin is used to configure, launch, and initialize the language server.

Installing nvim-lspconfig

Install using, for example, vim-plug:

Plug 'neovim/nvim-lspconfig'

Enable the language server

Add the following setup call to your init.vim to make the language server attach to Erlang files:

lua require'lspconfig'.erlangls.setup{}

Now, when you open an Erlang file you should see a message like this:

LSP[erlangls][Info] Erlang LS (in <your-project>), version: ..., OTP version: ...

Test it by writing some incorrect code. You should see a syntax error message. Run :LspInfo to get the status of active and configured language servers.

Configuration

There are no default keybindings for the LSP commands. You can find a good example on how to set these up in the Keybindings and completion section on the nvim-lspconfig plugin page. The idea is to create a function that sets up your keybindings and configuration, which is passed to the setup function in the previous section. This function is then called when the Erlang language server is attached. See the Neovim LSP documentation for more information.

Example

" init.vim
...
lua require'lspconfig'.erlangls.setup{}

lua << EOF
local nvim_lsp = require('lspconfig')
local on_attach = function(client, bufnr)
  local function buf_set_keymap(...) vim.api.nvim_buf_set_keymap(bufnr, ...) end
  local function buf_set_option(...) vim.api.nvim_buf_set_option(bufnr, ...) end

  buf_set_option('omnifunc', 'v:lua.vim.lsp.omnifunc')

  -- Mappings.
  local opts = { noremap=true, silent=true }
  buf_set_keymap('n', 'gD', '<cmd>lua vim.lsp.buf.declaration()<CR>', opts)
  buf_set_keymap('n', 'gd', '<cmd>lua vim.lsp.buf.definition()<CR>', opts)
  buf_set_keymap('n', 'K', '<cmd>lua vim.lsp.buf.hover()<CR>', opts)
  buf_set_keymap('n', 'gi', '<cmd>lua vim.lsp.buf.implementation()<CR>', opts)
  buf_set_keymap('n', '<C-k>', '<cmd>lua vim.lsp.buf.signature_help()<CR>', opts)
  buf_set_keymap('n', '<space>wa', '<cmd>lua vim.lsp.buf.add_workspace_folder()<CR>', opts)
  buf_set_keymap('n', '<space>wr', '<cmd>lua vim.lsp.buf.remove_workspace_folder()<CR>', opts)
  buf_set_keymap('n', '<space>wl', '<cmd>lua print(vim.inspect(vim.lsp.buf.list_workspace_folders()))<CR>', opts)
  buf_set_keymap('n', '<space>D', '<cmd>lua vim.lsp.buf.type_definition()<CR>', opts)
  buf_set_keymap('n', '<space>rn', '<cmd>lua vim.lsp.buf.rename()<CR>', opts)
  buf_set_keymap('n', '<space>ca', '<cmd>lua vim.lsp.buf.code_action()<CR>', opts)
  buf_set_keymap('n', 'gr', '<cmd>lua vim.lsp.buf.references()<CR>', opts)
  buf_set_keymap('n', '<space>e', '<cmd>lua vim.lsp.diagnostic.show_line_diagnostics()<CR>', opts)
  buf_set_keymap('n', '[d', '<cmd>lua vim.lsp.diagnostic.goto_prev()<CR>', opts)
  buf_set_keymap('n', ']d', '<cmd>lua vim.lsp.diagnostic.goto_next()<CR>', opts)
  buf_set_keymap('n', '<space>q', '<cmd>lua vim.lsp.diagnostic.set_loclist()<CR>', opts)

  -- Set some keybinds conditional on server capabilities
  if client.resolved_capabilities.document_formatting then
    buf_set_keymap("n", "<space>f", "<cmd>lua vim.lsp.buf.formatting()<CR>", opts)
  end
  if client.resolved_capabilities.document_range_formatting then
    buf_set_keymap("v", "<space>f", "<cmd>lua vim.lsp.buf.range_formatting()<CR>", opts)
  end

  -- Set autocommands conditional on server_capabilities
  if client.resolved_capabilities.document_highlight then
    vim.api.nvim_exec([[
      hi LspReferenceRead cterm=bold ctermbg=Grey guibg=LightYellow
      hi LspReferenceText cterm=bold ctermbg=Grey guibg=LightYellow
      hi LspReferenceWrite cterm=bold ctermbg=Grey guibg=LightYellow
      augroup lsp_document_highlight
        autocmd! * <buffer>
        autocmd CursorHold <buffer> lua vim.lsp.buf.document_highlight()
        autocmd CursorMoved <buffer> lua vim.lsp.buf.clear_references()
      augroup END
    ]], false)
  end
end

 -- Use a loop to conveniently both setup defined servers 
 -- and map buffer local keybindings when the language server attaches
 local servers = { "erlangls" }
 for _, lsp in ipairs(servers) do
  nvim_lsp[lsp].setup { on_attach = on_attach }
 end

EOF

Tips and tricks

Run :h vim.diagnostic.config inside Neovim for instructions on how to display diagnostics. :h vim.lsp.codelens.refresh describes how to show code lenses.