strict.lua

--------------------------------------------------------------------------------
--- Global environment protection
-- @module lua-nucleo.strict
-- This file is a part of lua-nucleo library
-- @copyright lua-nucleo authors (see file `COPYRIGHT` for the license)
--------------------------------------------------------------------------------

local type, pairs, error, rawget, rawset, tostring
    = type, pairs, error, rawget, rawset, tostring

local declared = { }

declare = function(name)
  declared[name] = true
end

exports = function(names)
  local name_type = type(names)
  if name_type == "table" then
    for k, name in pairs(names) do
      declare(name)
    end
  elseif name_type == "string" then
    declare(names)
  else
    error("Bad type for export: " .. name_type, 2)
  end
end

is_declared = function(name)
  return declared[name] == true
end

get_declared_iter_ = function()
  return pairs(declared)
end

uninstall_strict_mode_ = function()
  setmetatable(_G, nil)
  declared = { }
end

if getmetatable(_G) ~= nil then
  error("_G already got metatable")
end

-- NOTE: declare global variables for interactive mode of Lua interpreter
declare('_PROMPT')
declare('_PROMPT2')

-- NOTE: declare global variables for Lua versions compatibility
declare('unpack')
declare('newproxy')
declare('loadstring')
declare('setfenv')

setmetatable(_G, {
  __index = function(t, k)
    if declared[k] then
      return rawget(t, k)
    end

    error("attempted to access undeclared global: "..tostring(k), 2)
  end;

  __newindex = function(t, k, v)
    if declared[k] then
      return rawset(t, k, v)
    end

    error("attempted to write to undeclared global: "..tostring(k), 2)
  end;
})