I received a nil value when attempting to override the mason-lspconfig handlers in my configuration using the following code.
There was a similar issue and solution raised on GitHub at nvim-luasnip, but it didn't solve my issue.
I think the issue is with mason-lspconfig as the setup handler is returning a nil value, but I couldn’t find a solution.
Code
return {
"neovim/nvim-lspconfig",
event = { "BufReadPre", "BufNewFile" },
dependencies = {
"hrsh7th/cmp-nvim-lsp",
{ "antosha417/nvim-lsp-file-operations", config = true },
{ "folke/neodev.nvim", opts = {} },
},
config = function()
-- import lspconfig plugin
local lspconfig = require("lspconfig")
-- import mason_lspconfig plugin
local mason_lspconfig = require("mason-lspconfig")
-- import cmp-nvim-lsp plugin
local cmp_nvim_lsp = require("cmp_nvim_lsp")
local keymap = vim.keymap -- for conciseness
vim.api.nvim_create_autocmd("LspAttach", {
group = vim.api.nvim_create_augroup("UserLspConfig", {}),
callback = function(ev)
-- Buffer local mappings.
-- See `:help vim.lsp.*` for documentation on any of the below functions
local opts = { buffer = ev.buf, silent = true }
-- set keybinds
opts.desc = "Show LSP references"
keymap.set("n", "gR", "<cmd>Telescope lsp_references<CR>", opts) -- show definition, references
opts.desc = "Go to declaration"
keymap.set("n", "gD", vim.lsp.buf.declaration, opts) -- go to declaration
opts.desc = "Show LSP definitions"
keymap.set("n", "gd", "<cmd>Telescope lsp_definitions<CR>", opts) -- show lsp definitions
opts.desc = "Show LSP implementations"
keymap.set("n", "gi", "<cmd>Telescope lsp_implementations<CR>", opts) -- show lsp implementations
opts.desc = "Show LSP type definitions"
keymap.set("n", "gt", "<cmd>Telescope lsp_type_definitions<CR>", opts) -- show lsp type definitions
opts.desc = "See available code actions"
keymap.set({ "n", "v" }, "<leader>ca", vim.lsp.buf.code_action, opts) -- see available code actions, in visual mode will apply to selection
opts.desc = "Smart rename"
keymap.set("n", "<leader>rn", vim.lsp.buf.rename, opts) -- smart rename
opts.desc = "Show buffer diagnostics"
keymap.set("n", "<leader>D", "<cmd>Telescope diagnostics bufnr=0<CR>", opts) -- show diagnostics for file
opts.desc = "Show line diagnostics"
keymap.set("n", "<leader>d", vim.diagnostic.open_float, opts) -- show diagnostics for line
opts.desc = "Go to previous diagnostic"
keymap.set("n", "[d", vim.diagnostic.goto_prev, opts) -- jump to previous diagnostic in buffer
opts.desc = "Go to next diagnostic"
keymap.set("n", "]d", vim.diagnostic.goto_next, opts) -- jump to next diagnostic in buffer
opts.desc = "Show documentation for what is under cursor"
keymap.set("n", "K", vim.lsp.buf.hover, opts) -- show documentation for what is under cursor
opts.desc = "Restart LSP"
keymap.set("n", "<leader>rs", ":LspRestart<CR>", opts) -- mapping to restart lsp if necessary
end,
})
-- used to enable autocompletion (assign to every lsp server config)
local capabilities = cmp_nvim_lsp.default_capabilities()
-- Change the Diagnostic symbols in the sign column (gutter)
local signs = { Error = " ", Warn = " ", Hint = " ", Info = " " }
for type, icon in pairs(signs) do
local hl = "DiagnosticSign" .. type
vim.fn.sign_define(hl, { text = icon, texthl = hl, numhl = "" })
end
mason_lspconfig.setup_handlers({
-- default handler for installed servers
function(server_name)
lspconfig[server_name].setup({
capabilities = capabilities,
})
["emmet_ls"] = function()
-- configure emmet language server
lspconfig["emmet_ls"].setup({
capabilities = capabilities,
filetypes = { "html", "typescriptreact", "javascriptreact", "css", "sass", "scss", "less", "svelte" },
})
end,
["lua_ls"] = function()
-- configure lua server (with special settings)
lspconfig["lua_ls"].setup({
capabilities = capabilities,
settings = {
Lua = {
-- make the language server recognize "vim" global
diagnostics = {
globals = { "vim" },
},
completion = {
callSnippet = "Replace",
},
},
},
})
end,
end,
})
end,
}
Error output
Failed to run `config` for nvim-lspconfig
...ister/.config/nvim/lua/meister/plugins/lsp/lspconfig.lua:81: attempt to call field 'setup_handlers' (a nil value)
# stacktrace:
- lua/meister/plugins/lsp/lspconfig.lua:81 _in_ **config**
- vim/_editor.lua:0
- /auto-session/lua/auto-session/init.lua:746
From version 2.0.0 released 06 May 2025, the handlers setting and setup_handlers() function have been removed. These have been replaced with the new native vim.lsp.config() API and a new automatic_enable setting.
An example setup is given on the version 2.0.0 release page:
-- Configure a server via `vim.lsp.config()` or `{after/}lsp/lua_ls.lua`
vim.lsp.config('lua_ls', {
settings = {
Lua = {
runtime = {
version = 'LuaJIT',
},
diagnostics = {
globals = {
'vim',
'require',
},
},
},
},
})
require("mason").setup()
-- Note: `nvim-lspconfig` needs to be in 'runtimepath' by the time you set up mason-lspconfig.nvim
require("mason-lspconfig").setup {
ensure_installed = { "lua_ls" }
}
For versions <2.0.0, the easiest solution is to call setup with your table of handler overrides like so:
mason_lspconfig.setup({handlers = {...}})
If you want to use setup_handlers, then I believe you have to call setup first, then setup_handlers like so:
mason_lspconfig.setup({
ensure_installed = {"lua_ls", 'emmet_ls'}
})
mason_lspconfig.setup_handlers({...})