nvim/lua/plugins/completion.lua

return {
  "hrsh7th/nvim-cmp",
  dependencies = {
    -- Adds LSP completion capabilities
    "hrsh7th/cmp-buffer",
    "hrsh7th/cmp-cmdline",
    "hrsh7th/cmp-nvim-lsp",
    "hrsh7th/cmp-path",
    "neovim/nvim-lspconfig",

    -- Snippets
    "L3MON4D3/LuaSnip", -- snippet engine
    "rafamadriz/friendly-snippets", -- pre-configured snippet texts
    "saadparwaiz1/cmp_luasnip", -- nvim-cmp source
  },
  event = { "InsertEnter", "CmdlineEnter" },
  opts = function()
    local cmp = require("cmp")
    local luasnip = require("luasnip")
    local has_words_before = function()
      unpack = unpack or table.unpack
      local line, col = unpack(vim.api.nvim_win_get_cursor(0))
      return col ~= 0 and vim.api.nvim_buf_get_lines(0, line - 1, line, true)[1]:sub(col, col):match("%s") == nil
    end

    require("mason").setup()
    require("luasnip.loaders.from_vscode").lazy_load()

    cmp.setup({
      -- keybinds
      -- see: https://github.com/hrsh7th/nvim-cmp/wiki/Example-mappings
      mapping = {
        ["<Tab>"] = cmp.mapping(function(fallback)
          if cmp.visible() then
            cmp.select_next_item()
          elseif luasnip.expand_or_jumpable() then
            luasnip.expand_or_jump()
          elseif has_words_before() then
            cmp.complete()
          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" }),

        ["<CR>"] = cmp.mapping.confirm(),
        ["<Up>"] = cmp.mapping.select_prev_item({ behavior = "select" }),
        ["<Down>"] = cmp.mapping.select_next_item({ behavior = "select" }),
      },

      -- snippet engine
      snippet = {
        expand = function(args)
          require("luasnip").lsp_expand(args.body)
        end,
      },

      -- completion source
      sources = cmp.config.sources({
        { name = "nvim_lsp" },
        { name = "luasnip" },
        { name = "buffer" },
        { name = "path" },
      }),
    })

    -- Use buffer source for `/` and `?`
    cmp.setup.cmdline({ "/", "?" }, {
      mapping = cmp.mapping.preset.cmdline(),
      sources = {
        { name = "buffer" },
      },
    })

    -- Use cmdline & path source for ':'
    cmp.setup.cmdline(":", {
      mapping = cmp.mapping.preset.cmdline(),
      sources = cmp.config.sources({
        { name = "path" },
        { name = "cmdline" },
      }),
    })
  end,
}