lua/etc/strict.lua

   1 --
   2 -- strict.lua
   3 -- checks uses of undeclared global variables
   4 -- All global variables must be 'declared' through a regular assignment
   5 -- (even assigning nil will do) in a main chunk before being used
   6 -- anywhere or assigned to inside a function.
   7 --
   8
   9 local mt = getmetatable(_G)
  10 if mt == nil then
  11   mt = {}
  12   setmetatable(_G, mt)
  13 end
  14
  15 mt.__declared = {}
  16
  17 local function what ()
  18   local d = debug.getinfo(3, "S")
  19   return d and d.what or "C"
  20 end
  21
  22 mt.__newindex = function (t, n, v)
  23   if not mt.__declared[n] then
  24     local w = what()
  25     if w ~= "main" and w ~= "C" then
  26       error("assign to undeclared variable '"..n.."'", 2)
  27     end
  28     mt.__declared[n] = true
  29   end
  30   rawset(t, n, v)
  31 end
  32
  33 mt.__index = function (t, n)
  34   if not mt.__declared[n] and what() ~= "C" then
  35     error("variable '"..n.."' is not declared", 2)
  36   end
  37   return rawget(t, n)
  38 end
  39