nvim/lua/init-cmp.lua

local cmp = require'cmp'
cmp.setup({
	formatting = {
		format = function(entry, vim_item)
			-- set a name for each source
			vim_item.menu = ({
				nvim_lsp = "[LSP]",
				path = "[Path]",
				buffer = "[Buffer]",
				ultisnips = "[UltiSnips]",
			})[entry.source.name]
			return vim_item
		end,
	},
	completion = {
		keyword_length = 1,
		max_item_count = 20,
		-- autocomplete = false
	},
	snippet = {
	  expand = function(args)
	    vim.fn["UltiSnips#Anon"](args.body)
	  end,
	},
	mapping = {
		['<C-d>'] = cmp.mapping.scroll_docs(-4),
		['<C-u>'] = cmp.mapping.scroll_docs(4),
		["<C-n>"] = cmp.mapping({
			i = function()
				if cmp.visible() then
					cmp.select_next_item({ behavior = cmp.SelectBehavior.Insert })
				else
					cmp.complete()
				end
			end,
		}),
	},
	sources = {
		{
			name = 'nvim_lsp',
			max_item_count = 8,
			keyword_length = 3,
		},
		{ name = 'path' },
		{
			name = 'buffer',
			keyword_length = 4,
			max_item_count = 20,
		},
		{
			name = 'ultisnips',
			priority_weight = 10,
			keyword_length = 1,
		},
	}
})