nvim/lua/conf/cmp.lua

local cmp = require'cmp'
cmp.setup({
  snippet = {
    expand = function(args)
      vim.fn["vsnip#anonymous"](args.body)
    end,
  },
  mapping = {
    ['<C-y>'] = cmp.mapping.confirm({ select = true }),
    ['<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()
      else
        fallback()
      end
    end
  },
  sources = {
    { name = 'nvim_lsp' },
    --{ name = 'buffer' },
    { name = 'vsnip' },
    --{ name = 'path' },
  }
})
local capabilities = vim.lsp.protocol.make_client_capabilities()
capabilities = require('cmp_nvim_lsp').update_capabilities(capabilities)