nvim-cmp and Completion

nvim-cmp is the most widely used Neovim completion engine. It aggregates completion sources (LSP, buffer words, file paths, snippets) and displays them in a popup menu.

Core Idea

nvim-cmp is a framework — it shows completions from multiple sources. Each source (LSP, buffer, path, luasnip) is a separate plugin registered with nvim-cmp.

Required Plugins

lua/plugins/completion.lua
return {
  {
    "hrsh7th/nvim-cmp",
    event = "InsertEnter",
    dependencies = {
      -- Sources
      "hrsh7th/cmp-nvim-lsp",      -- LSP completions
      "hrsh7th/cmp-buffer",         -- Buffer words
      "hrsh7th/cmp-path",           -- File paths
      "hrsh7th/cmp-cmdline",        -- Command-line completion
      "saadparwaiz1/cmp_luasnip",   -- Snippet completions

      -- Snippets engine
      {
        "L3MON4D3/LuaSnip",
        version = "v2.*",
        build = "make install_jsregexp",
        dependencies = {
          "rafamadriz/friendly-snippets", -- pre-made snippets
        },
        config = function()
          require("luasnip.loaders.from_vscode").lazy_load()
        end,
      },

      -- Icons in completion menu
      "onsails/lspkind.nvim",
    },
    config = function()
      local cmp = require("cmp")
      local luasnip = require("luasnip")
      local lspkind = require("lspkind")

      cmp.setup({
        snippet = {
          expand = function(args)
            luasnip.lsp_expand(args.body)
          end,
        },

        -- Key mappings
        mapping = cmp.mapping.preset.insert({
          ["&lt;C-b&gt;"] = cmp.mapping.scroll_docs(-4),
          ["&lt;C-f&gt;"] = cmp.mapping.scroll_docs(4),
          ["&lt;C-Space&gt;"] = cmp.mapping.complete(),
          ["&lt;C-e&gt;"] = cmp.mapping.abort(),
          ["&lt;CR&gt;"] = cmp.mapping.confirm({ select = false }),
          ["&lt;Tab&gt;"] = 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" }),
          ["&lt;S-Tab&gt;"] = 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 (in priority order)
        sources = cmp.config.sources({
          { name = "nvim_lsp", priority = 1000 },
          { name = "luasnip", priority = 750 },
          { name = "path", priority = 500 },
        }, {
          { name = "buffer", priority = 250, keyword_length = 3 },
        }),

        -- Appearance
        formatting = {
          format = lspkind.cmp_format({
            mode = "symbol_text",
            maxwidth = 50,
            ellipsis_char = "...",
            symbol_map = {
              Text = "󰉿",
              Method = "󰆧",
              Function = "󰊕",
              Constructor = "",
              Variable = "󰀫",
              Class = "󰠱",
              Interface = "",
              Module = "",
              Property = "󰜢",
              Snippet = "",
              Color = "󰏘",
              File = "󰈙",
              Folder = "󰉋",
            },
          }),
        },

        -- Window
        window = {
          completion = cmp.config.window.bordered(),
          documentation = cmp.config.window.bordered(),
        },

        experimental = {
          ghost_text = true,   -- show preview inline
        },
      })

      -- Cmdline completions
      cmp.setup.cmdline({ "/", "?" }, {
        mapping = cmp.mapping.preset.cmdline(),
        sources = { { name = "buffer" } },
      })

      cmp.setup.cmdline(":", {
        mapping = cmp.mapping.preset.cmdline(),
        sources = cmp.config.sources({
          { name = "path" },
          { name = "cmdline" },
        }),
      })
    end,
  },
}

Completion Key Bindings

Key	Action
<C-Space>	Force open completion menu
<Tab>	Next item / expand snippet
<S-Tab>	Previous item / jump back in snippet
<CR>	Confirm selection
<C-e>	Abort / close menu
<C-b> / <C-f>	Scroll docs up/down

Completion Sources Reference

Source Plugin	Name	Provides
cmp-nvim-lsp	nvim_lsp	Language server completions
cmp-buffer	buffer	Words in open buffers
cmp-path	path	File system paths
cmp-cmdline	cmdline	Cmdline completion
cmp_luasnip	luasnip	Snippet completions
cmp-nvim-lua	nvim_lua	Neovim Lua API
cmp-calc	calc	Math expressions

Writing Custom Snippets with LuaSnip

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

-- Define a custom PHP snippet
ls.add_snippets("php", {
  s("func", {
    t("function "),
    i(1, "functionName"),
    t("("),
    i(2, "$param"),
    t({ ") {", "\t" }),
    i(0),
    t({ "", "}" }),
  }),
})

In LazyVim

LazyVim Context

As of late 2024, LazyVim switched from nvim-cmp to blink.cmp as its default completion engine. blink.cmp is significantly faster as it is written in Rust. The concepts remain the same, but the configuration syntax is completely different.

Aspect	Vanilla Neovim	LazyVim
Engine	nvim-cmp	blink.cmp (default)
Snippets	LuaSnip or native	Native snippets via blink.cmp
Sources	Manual cmp-nvim-lsp, etc.	Bundled in blink.cmp providers

Required Plugins​

Completion Key Bindings​

Completion Sources Reference​

Writing Custom Snippets with LuaSnip​

In LazyVim​

Related​

What's Next​

Required Plugins

Completion Key Bindings

Completion Sources Reference

Writing Custom Snippets with LuaSnip

In LazyVim

Related

What's Next