the nothing language server

nothing-ls.lua

-- NOTE: to TC of the future
-- if you attempt to make an actual language server, *please* read the specification
-- https://microsoft.github.io/language-server-protocol/specifications/specification-current
-- here's a sample server so you can read along too, in case you ever forget how it's done
--
-- NOTE: for everyone else
-- the nothing language server: a (really buggy) language server that does nothing
-- this thing is public domain (we're talking https://unlicense.org/)
--
-- NOTE: for both
-- it doesn't use sockets, it uses standard I/O
-- go look up sockets somewhere else fool
-- (I don't know sockets either)

-- you'll have to use https://github.com/rxi/json.lua for this one,
-- but any json library with a "decode" and "encode" methods will suffice
local json = require 'json'

-- shorthand for sending a table back
local function send(t)
	t.jsonrpc = '2.0'
	local out = json.encode(t)
	-- output the header, and then the content
	-- https://microsoft.github.io/language-server-protocol/specifications/specification-current#headerPart
	io.stdout:write('Content-Length: ', #out)
	io.stdout:write('\r\n\r\n', out, '\n')
end

-- these are the most important streams in this program
-- so it just makes sense to disable buffering on them
io.stdin:setvbuf 'no'
io.stdout:setvbuf 'no'

local intialized = false

-- all requests sent by the client that runs this server
-- will be logged in this file, might be helpful for actual lsp development
local requestsSent = assert(io.open('requests.txt', 'w+b'))

while true do
	local input = io.read()

	if input then
		-- this is *not* a good way to parse the header.
		-- please just parse it properly.
		local len = tonumber(assert(input:match 'Content%-Length: (%d+)'))
		if input:match 'Content%-Type: .-' then input = io.read() end
		input = io.read() -- obligatory empty line

		input = io.read(len)
		requestsSent:write(input, '\n')
		local request = json.decode(input)

		if not intialized then
			-- https://microsoft.github.io/language-server-protocol/specifications/specification-current#initialize
			if request.method == 'exit' then
				requestsSent:close()
				os.exit(-1)
			elseif request.method == 'initialize' then
				send { id = request.id, method = 'initialized' }
			else
				-- spoiler: -32002 means uninitalized server
				send { id = request.id, code = -32002 }
			end
		else
			-- do nothing
			-- yeah, mindblowing
		end
	end

	-- do *not* yield using this.
	-- I'm pretty sure it will either completely
	-- freeze both the server and the client, or
	-- cause something else to happen, but it's
	-- probably not good, I have not tried it
	-- and nor will I
	os.execute 'sleep 1'
end

-- now you'll have to go on from here, good luck and hope you arrive at your destination sane :)