Toy Language Server

This is a toy project that I'm building from scratch without any external dependencies and only using python's stdlib.

Motivation

My curiosity about how code completion and other language support features work in code editors like VS Code and Neovim led me to build my own language server from scratch as a learning experience and to improve my skills as a developer.

Goal

In the longrun my goal is to build a language server,

• for: LÖVE 2D framework
• with: Python
• over: STDIO
• supporting: code completion
• for client: Neovim

Progress

• Handle initialization
• Handle basic server lifecycle messages
  . . .

Setup

Setting up the server with Neovim is really easy, inside Neovim's config folder create a file init.lua and add this config.

local client = vim.lsp.start_client({
	name = "your language server name",
	cmd = {"python", "path\\to\\script.py"} -- escape the '\' (for Windows)
})

if not client then
	vim.notify("Couldn't setup the client.")
	return 
end

-- the server will be attached when a markdown file is opened, specify the type you want to work with
vim.api.nvim_create_autocmd(
    "FileType",
    {pattern="markdown", callback=function() vim.lsp.buf_attach_client(0, client) end}
)

When you open a markdown file, you can check if the server is actually up by executing checkhealth lsp in COMMAND mode (press colon in NORMAL mode). See %localappdata%\ToyLanguageServer\Log\server.log for viewing the events and actions the server performs.

Helpful Resources

• Language Server Protocol specification.
• JSON-RPC specification.
• TJ DeVries's "LSP from scratch" video (Go implementation).