Vim Completion Configuration

A Bit of History

Vim has built-in support for completions in insert or replace modes, mostly based on the content of the current file and included files. By default, it uses separate Emacs-style key bindings (<C-x C-key>) for different kinds of completions. See :help ins-completion for more information.

The modern approach is utilizing language server protocol, a.k.a. LSP, and machine learning.

The concept of LSP is pioneered by vscode, so a lot of language servers are written in Node.js and TypeScript. While mostly used for LSP, CoC brings the ecosystem of vscode extensions to vim, which makes porting them to vim easier.

Then Neovim 0.5+ introduces native LSP support, based on Lua instead of Node.js. However, as mentioned above, since a lot of language servers are written in Node.js, most likely Node.js is still needed.

Machine Learning based Completion

Popular options of machine learning assisted completion are:

• Tabnine
• GitHub Copilot
• Codeium
• Amazon CodeWhisperer

I have used Tabnine (free plan) for a while. It does not include whole line and full-function code completion. Although Tabnine Pro offers offline installation, it requires contacting sales. Its free plan is based on the cloud, just like Copilot.

Tabnine Pro is $12 per month, slightly higher than Copilot ($10 per month). And qualified open source project contributors can use Copilot for free.

Both Codeium and Amazon CodeWhisperer are free for personal use. Currently, CodeWhisperer only supports VSCode and JetBrain IDEs.

I use Copilot and Codeium at the same time under Neovim, where nvim-cmp can use both as a completion source. Codeium tends to offer multi-line completion as a whole, and Copilot are more likely to provide completions line by line. The completion quality is roughly the same, as I have experienced.

My LazyVim Configuration for Copilot and Codeium

-- lua/config/lazy.lua
require("lazy").setup({
  spec = {
    { "LazyVim/LazyVim", import = "lazyvim.plugins" },
    { import = "lazyvim.plugins.extras.coding.copilot" },
    { import = "plugins" },
  },
})

-- lua/plugins/cmp.lua
return {
  -- The official plugin does not support nvim-cmp, use a community one instead.
  {
    "jcdickinson/codeium.nvim",
    dependencies = {
      "nvim-lua/plenary.nvim",
      "hrsh7th/nvim-cmp",
    },
    config = function()
      require("codeium").setup({})
    end,
  },
}