Correct sumneko lua lsp setup for init.lua and plugin development

lua-lsp.lua

-- put this file somewhere in your nvim config, like: ~/.config/nvim/lua/config/lua-lsp.lua
-- usage: require'lspconfig'.sumneko_lua.setup(require("config.lua-lsp"))

local library = {}

local path = vim.split(package.path, ";")

-- this is the ONLY correct way to setup your path
table.insert(path, "lua/?.lua")
table.insert(path, "lua/?/init.lua")

local function add(lib)
  for _, p in pairs(vim.fn.expand(lib, false, true)) do
    p = vim.loop.fs_realpath(p)
    library[p] = true
  end
end

-- add runtime
add("$VIMRUNTIME")

-- add your config
add("~/.config/nvim")

-- add plugins
-- if you're not using packer, then you might need to change the paths below
add("~/.local/share/nvim/site/pack/packer/opt/*")
add("~/.local/share/nvim/site/pack/packer/start/*")

return {
  -- delete root from workspace to make sure we don't trigger duplicate warnings
  on_new_config = function(config, root)
    local libs = vim.tbl_deep_extend("force", {}, library)
    libs[root] = nil
    config.settings.Lua.workspace.library = libs
    return config
  end,
  settings = {
    Lua = {
      runtime = {
        -- Tell the language server which version of Lua you're using (most likely LuaJIT in the case of Neovim)
        version = "LuaJIT",
        -- Setup your lua path
        path = path
      },
      completion = { callSnippet = "Both" },
      diagnostics = {
        -- Get the language server to recognize the `vim` global
        globals = { "vim" }
      },
      workspace = {
        -- Make the server aware of Neovim runtime files
        library = library,
        maxPreload = 2000,
        preloadFileSize = 50000
      },
      -- Do not send telemetry data containing a randomized but unique identifier
      telemetry = { enable = false }
    }
  }
}

types.lua

-- put this file somewhere in your nvim config, like: ~/.config/nvim/lua/types.lua
-- DONT require this file anywhere. It's simply there for the lsp server.

-- this code seems weird, but it hints the lsp server to merge the required packages in the vim global variable
vim = require("vim.shared")
vim = require("vim.uri")
vim = require("vim.inspect")

-- let sumneko know where the sources are for the global vim runtime
vim.lsp = require("vim.lsp")
vim.treesitter = require("vim.treesitter")
vim.highlight = require("vim.highlight")

That's awesome, thanks for doing this! I will install it and check soon.