neovim-config/lua/plugins/nvim-cmp.lua

local cmp = require('cmp')
local lspkind = require('lspkind')

cmp.setup({
  experimental = { ghost_text = true },
  snippet = {
    -- REQUIRED - you must specify a snippet engine
    expand = function(args)
      vim.fn['vsnip#anonymous'](args.body) -- For `vsnip` users.
      -- require('luasnip').lsp_expand(args.body) -- For `luasnip` users.
      -- require('snippy').expand_snippet(args.body) -- For `snippy` users.
      -- vim.fn["UltiSnips#Anon"](args.body) -- For `ultisnips` users.
    end,
  },
  window = {
    -- completion = cmp.config.window.bordered(),
    -- documentation = cmp.config.window.bordered(),
  },
  mapping = cmp.mapping.preset.insert({
    ['<C-b>'] = cmp.mapping.scroll_docs(-4),
    ['<C-f>'] = cmp.mapping.scroll_docs(4),
    ['<C-Space>'] = cmp.mapping.complete(),
    ['<C-e>'] = cmp.mapping.abort(),
    ['<CR>'] = cmp.mapping.confirm({ select = true }), -- Accept currently selected item. Set `select` to `false` to only confirm explicitly selected items.
    ["<Tab>"] = cmp.mapping(function(fallback)
      if cmp.visible() then
          cmp.select_next_item()
      else
        fallback()
      end
    end, { "i", "s" }),
    ["<S-Tab>"] = cmp.mapping(function(fallback)
      if cmp.visible() then
          cmp.select_prev_item()
      else
        fallback()
      end
    end, { "i", "s" }),
  }),
  sources = cmp.config.sources({
    {
      name = 'nvim_lsp_signature_help',
      priority = 100,
      group_index = 1,
    },
    {
      name = 'nvim_lsp',
      priority = 100,
      group_index = 1,
    },
    {
      name = 'cmp_tabnine',
      priority = 90,
      group_index = 2,
    },
    {
      name = 'buffer',
      priority = 80,
      group_index = 3,
    },
    {
      name = 'path',
      priority = 80,
      group_index = 3,
    },
    { name = 'vsnip' }, -- For vsnip users.
    -- { name = 'luasnip' }, -- For luasnip users.
    -- { name = 'ultisnips' }, -- For ultisnips users.
    -- { name = 'snippy' }, -- For snippy users.
  }),
  sorting = {
    comparators = {
      function(...) return require('cmp_buffer'):compare_locality(...) end,
    }
  },
  formatting = {
    format = lspkind.cmp_format({
      mode = 'symbol_text',
      maxwidth = 50,
      ellipsis_char = '…',
    })
  }
})

-- Set configuration for specific filetype.
cmp.setup.filetype('gitcommit', {
  sources = cmp.config.sources({
    { name = 'cmp_git' }, -- You can specify the `cmp_git` source if you were installed it.
  }, {
    { name = 'buffer' },
  })
})

-- Use buffer source for `/` and `?` (if you enabled `native_menu`, this won't work anymore).
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', keyword_pattern=[=[[^[:blank:]\!]*]=], keyword_length=3 }
  })
})

-- Add additional capabilities supported by nvim-cmp
local capabilities = require('cmp_nvim_lsp').default_capabilities()

local lspconfig = require("lspconfig")

-- Enable some language servers with the additional completion capabilities offered by nvim-cmp
local servers = { 'pyright', 'tsserver', 'html', 'cssls' }
for _, lsp in ipairs(servers) do
  lspconfig[lsp].setup({
    -- on_attach = my_custom_on_attach,
    capabilities = capabilities,
  })
end

return {
  capabilities,
}