Mason and lspconfig

Mason and lspconfig

The division of labor#

• mason.nvim — a package manager for editor tooling. It downloads language servers (and formatters, linters, debug adapters) into Neovim’s data directory, no system package manager involved.
• nvim-lspconfig — a data package: per-server launch commands, filetypes, and root-detection rules.
• Neovim 0.11+ — provides the native activation: vim.lsp.config() to adjust a server, vim.lsp.enable() to turn it on.

Setup#

With the plugins installed (vim-plug era):

require('mason').setup()
require('mason-lspconfig').setup({ensure_installed = {'lua_ls'}})

vim.lsp.config('lua_ls', {settings = {Lua = {diagnostics = {globals = {'vim'}}}}})

ensure_installed makes Mason fetch the server automatically; you can also install interactively with :Mason or :MasonInstall lua-language-server.

The vim.lsp.config call deep-merges settings over the lspconfig defaults — here telling lua-language-server that vim is a known global, which silences the most famous false diagnostic in Neovim configs.

One PATH gotcha worth knowing#

Mason installs binaries into its own bin directory and puts it on Neovim’s PATH when mason.nvim loads. If mason is lazy-loaded, a file opened directly from the shell (nvim foo.lua) can attach before that happens — and the server silently fails to start. The robust fix is one early line in init.lua:

vim.env.PATH = vim.fn.stdpath('data') .. '/mason/bin:' .. vim.env.PATH

The course repo’s config ships with this fix in place.

Useful keymaps#

Neovim 0.11+ provides defaults (grn rename, grr references, gra code action, K hover, [d/]d diagnostics). The one big omission is go-to-definition:

vim.keymap.set("n", "gd", vim.lsp.buf.definition, {desc="Go to definition"})