Neovim

The ELP project can be used as a language server in Neovim.

Installation

mason.nvim

The easiest way to install the ELP server is to use mason.nvim, a package manager focused on language servers, linters and similar tools. If you use Neovim for programming, you likely already have mason.nvim installed. It is also included in all the most popular "batteries included" configurations/distributions of Neovim such kickstart.nvim, LazyVim, NVChad and others.

With mason.nvim installed, you can install the ELP server by running the following command:

:MasonInstall elp

from within Neovim.

Alternatively you can run :Mason and browse the list of available packages, then press i when elp is highlighted.

Updating ELP

You can update all packages managed by mason.nvim by running :Mason and pressing U.

Manual installation

Alternatively, if you don't have mason.nvim installed, you can install the ELP binary and configure key mappings manually.

Example config

Here is an example user config to be placed in your init.vim file (~/.config/nvim/init.vim on Unix systems):

nnoremap <SPACE> <Nop>
let mapleader=" "

call plug#begin()
Plug 'neovim/nvim-lspconfig'
call plug#end()

lua <<EOF
local opts = { noremap=true, silent=true }
vim.api.nvim_set_keymap('n', '<leader>e', '<cmd>lua vim.diagnostic.open_float()<CR>', opts)

local on_attach = function(client, bufnr)
  vim.api.nvim_buf_set_option(bufnr, 'omnifunc', 'v:lua.vim.lsp.omnifunc')
  vim.api.nvim_buf_set_keymap(bufnr, 'n', 'gd', '<cmd>lua vim.lsp.buf.definition()<CR>', opts)
  vim.api.nvim_buf_set_keymap(bufnr, 'n', 'K', '<cmd>lua vim.lsp.buf.hover()<CR>', opts)
  vim.api.nvim_buf_set_keymap(bufnr, 'n', '<leader>rn', '<cmd>lua vim.lsp.buf.rename()<CR>', opts)
  vim.api.nvim_buf_set_keymap(bufnr, 'n', 'gr', '<cmd>lua vim.lsp.buf.references()<CR>', opts)
  vim.api.nvim_buf_set_keymap(bufnr, 'n', '<leader>ca', '<cmd>lua vim.lsp.buf.code_action()<CR>', opts)
  if client.server_capabilities.inlayHintProvider then
    vim.api.nvim_buf_set_keymap(bufnr, 'n', '<leader>ih',
      '<cmd>lua vim.lsp.inlay_hint.enable(not vim.lsp.inlay_hint.is_enabled())<CR>',
      { noremap=true, silent=true, desc = '[T]oggle Inlay [H]ints' })
  end
end

require('lspconfig').elp.setup {
  on_attach = on_attach,
  settings = {
    elp = {
      diagnostics = {
        disabled = {
          "W0030",
          "W0031",
          "W0032"
        }
      }
    }
  }
}
EOF

In this example config, the Leader key is mapped to <space>.

vim-plug, a minimalist Vim plugin manager is used to install nvim-lspconfig.

The Lua code then defines the following key mappings in "normal" Vim mode:

• <space>e displays diagnostics, for example the red text in above screenshot
• gd goes to the definition
• K shows function specs
• <space>rn renames a variable
• gr shows references
• <space>ca suggests code actions for warnings displayed ELP
• <space>ih toggles displaying inlay hints (for example function argument hints)

Finally, you can disable some warnings globally for all your Erlang projects.

Troubleshooting

:LspInfo shows the current status of the LSP client.

:LspLog opens the log file for the LSP client, which can be useful for debugging.