lspconfig - Implement addToDictionary for ltex

ltex.lua

local S = {}

-- define the files for each language
-- new words will be added to the last file in the language table
S.dictionaries = {
	["en-US"] = { vim.fn.stdpath("config") .. "/spell/en.txt" },
}

-- function to avoid interacting with the table directly
function S.getDictFiles(lang)
	local files = S.dictionaries[lang]
	if files then
		return files
	else
		return nil
	end
end

-- combine words from all the files. Each line should contain one word
function S.readDictFiles(lang)
	local files = S.getDictFiles(lang)
	local dict = {}
	if files then
		for _, file in ipairs(files) do
			local f = io.open(file, "r")
			if f then
				for l in f:lines() do
					table.insert(dict, l)
				end
            else
                print("Can not read dict file %q", file)
			end
		end
    else
        print("Lang %q has no files", lang)
	end
	return dict
end

-- Append words to the last element of the language files
function S.addWordsToFiles(lang, words)
	local files = S.getDictFiles(lang)
	if not files then
		return print("no dictionary file defined for lang %q", lang)
	else
		local file = io.open(files[#files - 0], "a+")
		if file then
            for _,word in ipairs(words) do
			file:write(word .. "\n")
            end
			file:close()
		else
			return print("Failed insert %q", vim.inspect(words))
		end
	end
end

-- The following part is a classic lspconfig config section 
local lspconfig = require("lspconfig")
-- notifying wkspc will refresh the settings that contain the dictionary
local wkspc = "workspace/didChangeConfiguration"
-- instead of looping through the list of clients and check client.name == 'ltex' (which many solutions out there are doing)
-- We attach the command function to the bufer then ltex is loaded
local function on_attach(client, bufnr)
	require("plugins.configs.lspconfig").on_attach(client, bufnr)
    -- the second argumeng is named 'ctx', but we don't need it here
    --- command = {argument={...}, command=..., title=...}
	local addToDict = function(command, _)
		for _, arg in ipairs(command.arguments) do
            -- not the most efficent way, we could readDictFiles once per lang
			for lang, words in pairs(arg.words) do
				S.addWordsToFiles(lang, words)
				client.config.settings.ltex.dictionary = {
					[lang] = S.readDictFiles(lang),
				}
			end
		end
        -- notify the client of the new settings
		return client.notify(wkspc, client.config.settings)
	end
    -- add the function to handle the command
    -- then lsp.commands does not find the handler, it will look at opts.handler["workspace/executeCommand"]
	vim.lsp.commands["_ltex.addToDictionary"] = addToDict
end
-- 'pluging.config.lspconfig' is from NvChad configuraion
lspconfig.ltex.setup({
	on_attach = on_attach,
	capabilities = require("plugins.configs.lspconfig").capabilities,
	filetypes = { "tex", "markdown" },
	settings = {
		ltex = {
			dictionary = {
				["en-US"] = S.readDictFiles("en-US"),
			},
		},
	},
})