nvim/ftplugin/rust.lua

local cmp_nvim_lsp = require 'cmp_nvim_lsp'
local capabilities = vim.lsp.protocol.make_client_capabilities()
capabilities.textDocument.completion.completionItem.snippetSupport = true
capabilities = cmp_nvim_lsp.default_capabilities(capabilities)

local function has_formatter(ft)
	local sources = require 'null-ls.sources'
	local available = sources.get_available(ft, 'NULL_LS_FORMATTING')
	return #available > 0
end

local function lsp_keymaps(bufnr)
	local opt = { noremap = true, silent = true }
	local keymap = vim.api.nvim_buf_set_keymap
	keymap(bufnr, 'n', 'gD', '<cmd>lua vim.lsp.buf.declaration()<CR>', opt)
	keymap(bufnr, 'n', 'gd', '<cmd>lua vim.lsp.buf.definition()<CR>', opt)
	keymap(bufnr, 'n', 'K', '<cmd>lua vim.lsp.buf.hover()<CR>', opt)
	keymap(bufnr, 'n', 'gI', '<cmd>lua vim.lsp.buf.implementation()<CR>', opt)
	keymap(bufnr, 'n', 'gr', '<cmd>TroubleToggle lsp_references<CR>', opt)
	keymap(bufnr, 'n', 'gl', '<cmd>lua vim.diagnostic.open_float()<CR>', opt)
	keymap(bufnr, 'n', '<leader>lf', '<cmd>lua vim.lsp.buf.format { async = true }<cr>', opt)
	keymap(bufnr, 'n', '<leader>li', '<cmd>LspInfo<cr>', opt)
	keymap(bufnr, 'n', '<leader>lI', '<cmd>LspInstallInfo<cr>', opt)
	keymap(bufnr, 'n', '<leader>la', '<cmd>lua vim.lsp.buf.code_action()<cr>', opt)
	keymap(bufnr, 'n', '<leader>lj', '<cmd>lua vim.diagnostic.goto_next({buffer=0})<cr>', opt)
	keymap(bufnr, 'n', '<leader>lk', '<cmd>lua vim.diagnostic.goto_prev({buffer=0})<cr>', opt)
	keymap(bufnr, 'n', '<leader>lr', '<cmd>lua vim.lsp.buf.rename()<cr>', opt)
	keymap(bufnr, 'n', '<leader>ls', '<cmd>lua vim.lsp.buf.signature_help()<CR>', opt)
	keymap(bufnr, 'n', '<leader>lq', '<cmd>lua vim.diagnostic.setloclist()<CR>', opt)
	keymap(bufnr, 'n', '<leader>e', '<cmd>lua vim.diagnostic.open_float()<CR>', opt)
end

local on_attach = function(client, bufnr)
	--[[ vim.api.nvim_buf_set_option(bufnr, 'omnifunc', 'v:lua.vim.lsp.omnifunc') ]]
	lsp_keymaps(bufnr)
	local ft = vim.api.nvim_buf_get_option(bufnr, 'filetype')
	local nls = require 'plugins.null-ls'

	local enable = false
	if has_formatter(ft) then
		enable = client.name == 'null-ls'
	else
		enable = not (client.name == 'null-ls')
	end

	client.server_capabilities.documentFormattingProvider = enable
end
require('rust-tools').setup {
	server = {
		on_attach = on_attach,
		standalone = false,
	},
}