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-b>'] = cmp.mapping.scroll_docs(-4),
    ['<C-f>'] = cmp.mapping.scroll_docs(4),
    ['<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 = cmp.config.sources({
    { name = 'nvim_lsp' },
    { name = 'vsnip' },
  },{
    { name = 'buffer' },
    --{ name = 'path' },
  }),
})

cmp.setup.cmdline({ '/', '?' }, {
  mapping = cmp.mapping.preset.cmdline(),
  sources = {
    { name = 'buffer' }
  }
})

-- Use cmdline & path source for ':' (if you enabled `native_menu`, this won't work anymore).
cmp.setup.cmdline(':', {
  mapping = cmp.mapping.preset.cmdline(),
  sources = cmp.config.sources({
    { name = 'path' }
  }, {
    { name = 'cmdline' }
  })
})