今天推荐用 nvim-cmp + LuaSnip，因为它同时覆盖 LSP 补全和片段。若你使用较新的 Neovim，也可以先用内置补全保持轻量。

把插件加进 Day07 的 require("lazy").setup({...}) 列表。Telescope 保留，新增 cmp 和 LuaSnip。

require("lazy").setup({
  {
    "nvim-telescope/telescope.nvim",
    branch = "0.1.x",
    dependencies = { "nvim-lua/plenary.nvim" },
  },
  {
    "hrsh7th/nvim-cmp",
    dependencies = {
      "hrsh7th/cmp-nvim-lsp",
      "hrsh7th/cmp-buffer",
      "hrsh7th/cmp-path",
      "L3MON4D3/LuaSnip",
      "saadparwaiz1/cmp_luasnip",
    },
  },
})

新增 lua/config/completion.lua，然后在 init.lua 里插件加载后 require 它。

local cmp = require("cmp")
local luasnip = require("luasnip")

cmp.setup({
  preselect = cmp.PreselectMode.None,
  completion = {
    completeopt = "menu,menuone,noinsert,noselect",
  },
  snippet = {
    expand = function(args)
      luasnip.lsp_expand(args.body)
    end,
  },
  mapping = cmp.mapping.preset.insert({
    ["<C-Space>"] = cmp.mapping.complete(),
    ["<C-e>"] = cmp.mapping.abort(),
    ["<CR>"] = cmp.mapping.confirm({ select = false }),
    ["<Tab>"] = cmp.mapping(function(fallback)
      if cmp.visible() then
        cmp.select_next_item()
      elseif luasnip.expand_or_jumpable() then
        luasnip.expand_or_jump()
      else
        fallback()
      end
    end, { "i", "s" }),
    ["<S-Tab>"] = cmp.mapping(function(fallback)
      if cmp.visible() then
        cmp.select_prev_item()
      elseif luasnip.jumpable(-1) then
        luasnip.jump(-1)
      else
        fallback()
      end
    end, { "i", "s" }),
  }),
  sources = cmp.config.sources({
    { name = "nvim_lsp" },
    { name = "luasnip" },
    { name = "path" },
  }, {
    { name = "buffer" },
  }),
})

LSP 客户端会告诉服务器自己支持哪些能力。接入 cmp 后，要把增强后的 completion capability 传给 gopls。

local capabilities = vim.lsp.protocol.make_client_capabilities()

local ok, cmp_lsp = pcall(require, "cmp_nvim_lsp")
if ok then
  capabilities = cmp_lsp.default_capabilities(capabilities)
end

-- inside vim.lsp.start({
--   name = "gopls",
--   cmd = { "gopls" },
--   root_dir = root_dir(),
--   on_attach = on_attach,
--   capabilities = capabilities,
-- })

新增 lua/config/snippets.lua。片段少一点，准一点。今天只保留四类：函数、测试、表驱动测试、error return。

local ls = require("luasnip")
local s = ls.snippet
local t = ls.text_node
local i = ls.insert_node

ls.add_snippets("go", {
  s("gofunc", {
    t("func "), i(1, "Name"), t("("), i(2), t({ ") {", "\t" }),
    i(0),
    t({ "", "}" }),
  }),
  s("gotest", {
    t("func Test"), i(1, "Name"), t({ "(t *testing.T) {", "\t" }),
    i(0),
    t({ "", "}" }),
  }),
  s("goerr", {
    t({ "if err != nil {", "\treturn " }), i(1, "err"),
    t({ "", "}" }),
  }),
  s("gotable", {
    t({ "tests := []struct {", "\tname string", "\tinput " }), i(1, "string"),
    t({ "", "\twant " }), i(2, "string"),
    t({ "", "}{", "\t{name: " }), i(3, "\"case\""),
    t(", input: "), i(4, "\"input\""),
    t(", want: "), i(5, "\"want\""),
    t({ "},", "}", "", "for _, tt := range tests {", "\tt.Run(tt.name, func(t *testing.T) {", "\t\t" }),
    i(0),
    t({ "", "\t})", "}" }),
  }),
})

回到 Day05 的项目，用补全和片段完成一次真实小改动。

记录你最后保留了哪些补全行为。以后觉得补全吵，先回来看这份日志，而不是继续加插件。

# Day08 completion and snippets log

## Completion
- engine:
- confirm key:
- manual trigger:
- preselect:

## Snippets
- gofunc:
- gotest:
- gotable:
- goerr:

## Validation
- LSP candidate tested:
- snippet expanded:
- go test result:

## Friction
- one completion behavior I disliked:
- one setting I changed: