How do I setup elixir-ls using nvim-lspconfig with autocompletion in neovim? - autocomplete

Question

I would like to set up the Elixir language server in Neovim using the built-in language server client and nvim-lspconfig.
Documentation for this seems to be spread out in multiple places:
nvim-lspconfig README
nvim-lspconfig wiki about autocomplete
nvim-lspconfig elixir-ls server configuration documentation
elixir-ls installation instructions
I am a little overwhelmed and have made multiple attempts to do this, but always give up without success. I also found a useful looking guide: How to Set Up Neovim for Elixir Development, but it makes quite a few assumptions, seems to eroneously do some configuration twice, and also switches config format halfway through, so wasn't a usable summary for me (after following the instructions, documentation popups were not working, and I was unable to scroll inside the autocomplete popups - I also had a lot of copy/pasted config I didn't understand).
So far I understand the required steps are:
Install neovim
Install elixir-ls manually (it doesn't seem to be possible currently to install via asdf due to a lack of ability to ask elixir-ls for its version)
Install required neovim plugins: nvim-lspconfig + whatever is required for autocomplete
Set up necessary config for nvim-lspconfig and autocomplete.
I have managed to do up to part-way through step 3, but have not sucesfully worked out the required dependencies and configuration for autocomplete.
What do I need to do to have a working elixir-ls setup in neovim, with autocomplete, using nvim-lspconfig and neovim's built-in language server client?

Answer 1

I managed to get everything working with the combination of some plugins for completion in neovim. They are:
hrsh7th/nvim-cmp - the autocompletion plugin
hrsh7th/cmp-nvim-lsp - the integration of nvim-cmp with neovim's LSP
L3MON4D3/LuaSnip - a snippets plugin
saadparwaiz1/cmp_luasnip - the snippets source for nvim-cmp
This is the same list of plugins from the nvim-cmp recommendation of neovim's Wiki.
I'm using packer to manage the plugins. I'm also installing the plugins before configuring them.
Here is the installation lines:
use 'neovim/nvim-lspconfig'
use 'nvim-treesitter/completion-treesitter' -- Only if you are using TS
use 'hrsh7th/nvim-cmp' -- Autocompletion plugin
use 'hrsh7th/cmp-nvim-lsp' -- LSP source for nvim-cmp
use 'saadparwaiz1/cmp_luasnip' -- Snippets source for nvim-cmp
use 'L3MON4D3/LuaSnip' -- Snippets plugin
And then the configuration part:
-- Add additional capabilities supported by nvim-cmp
local capabilities = vim.lsp.protocol.make_client_capabilities()
capabilities = require('cmp_nvim_lsp').update_capabilities(capabilities)
-- Configure ElixirLS as the LSP server for Elixir.
require'lspconfig'.elixirls.setup{
cmd = { "/home/my-user/path-to/elixir-ls/release/language_server.sh" },
-- on_attach = custom_attach, -- this may be required for extended functionalities of the LSP
capabilities = capabilities,
flags = {
debounce_text_changes = 150,
},
elixirLS = {
dialyzerEnabled = false,
fetchDeps = false,
};
}
local luasnip = require 'luasnip'
-- nvim-cmp
local cmp = require 'cmp'
cmp.setup {
snippet = {
expand = function(args)
require('luasnip').lsp_expand(args.body)
end,
},
mapping = {
['<C-p>'] = cmp.mapping.select_prev_item(),
['<C-n>'] = cmp.mapping.select_next_item(),
['<C-d>'] = cmp.mapping.scroll_docs(-4),
['<C-f>'] = cmp.mapping.scroll_docs(4),
['<C-Space>'] = cmp.mapping.complete(),
['<C-e>'] = cmp.mapping.close(),
['<CR>'] = cmp.mapping.confirm {
behavior = cmp.ConfirmBehavior.Replace,
select = true,
},
['<Tab>'] = function(fallback)
if cmp.visible() then
cmp.select_next_item()
elseif luasnip.expand_or_jumpable() then
luasnip.expand_or_jump()
else
fallback()
end
end,
['<S-Tab>'] = function(fallback)
if cmp.visible() then
cmp.select_prev_item()
elseif luasnip.jumpable(-1) then
luasnip.jump(-1)
else
fallback()
end
end,
},
sources = {
{ name = 'nvim_lsp' },
{ name = 'luasnip' },
},
}
You can find all my neovim config in my dotfiles repo: https://github.com/philss/dotfiles
For reference, here is the nvim version I'm using (installed from source):
NVIM v0.7.0-dev+864-g2818de8b7
Build type: RelWithDebInfo
LuaJIT 2.1.0-beta3
Features: +acl +iconv +tui

Answer 2

In addition to the accepted answer, I suggest installing language server via Homebrew or similar instead of cloning repo and compiling. Philip's answer is correct. Just make your life easier by using a package manager for language server installation.
If you use LunarVim, which is like a NeoVim IDE, the configuration is minimal.
Nearly all dependencies for completion are already installed.
I also found it is better for Mac users to use Homebrew to install Elixir Language Server like so:
brew install elixir-ls
You don't need to keep track of the updates manually. It is usually upgraded along with other dev dependencies via brew update && brew upgrade.
Try this for LunarVim:
-- generic LSP settings
--
-- ---#usage disable automatic installation of servers
-- lvim.lsp.automatic_servers_installation = false
local lspconfig = require("lspconfig")
-- Neovim doesn't support snippets out of the box, so we need to mutate the
-- capabilities we send to the language server to let them know we want snippets.
local capabilities = vim.lsp.protocol.make_client_capabilities()
capabilities.textDocument.completion.completionItem.snippetSupport = true
-- ---configure a server manually. !!Requires `:LvimCacheReset` to take effect!!
-- ---see the full default list `:lua print(vim.inspect(lvim.lsp.automatic_configuration.skipped_servers))`
-- vim.list_extend(lvim.lsp.automatic_configuration.skipped_servers, { "pyright" })
-- local opts = {} -- check the lspconfig documentation for a list of all possible options
-- require("lvim.lsp.manager").setup("pyright", opts)
-- Elixir LS
lspconfig.elixirls.setup {
cmd = { "/usr/local/Cellar/elixir-ls/0.10.0/libexec/language_server.sh" },
-- on_attach = custom_attach, -- this may be required for extended functionalities of the LSP
capabilities = capabilities,
flags = {
debounce_text_changes = 150,
},
elixirLS = {
dialyzerEnabled = false,
fetchDeps = false,
};
}