Recreating setfenv() in Lua 5.2

Question

How can I recreate the functionality of setfenv in Lua 5.2? I\'m having some trouble understanding exactly how you are supposed to use the new _ENV

Answer 1

To recreate setfenv/getfenv in Lua 5.2 you can do the following:

if not setfenv then -- Lua 5.2
  -- based on http://lua-users.org/lists/lua-l/2010-06/msg00314.html
  -- this assumes f is a function
  local function findenv(f)
    local level = 1
    repeat
      local name, value = debug.getupvalue(f, level)
      if name == '_ENV' then return level, value end
      level = level + 1
    until name == nil
    return nil end
  getfenv = function (f) return(select(2, findenv(f)) or _G) end
  setfenv = function (f, t)
    local level = findenv(f)
    if level then debug.setupvalue(f, level, t) end
    return f end
end

RPFeltz's answer (load(string.dump(f)...)) is a clever one and may work for you, but it doesn't deal with functions that have upvalues (other than _ENV).

There is also compat-env module that implements Lua 5.1 functions in Lua 5.2 and vice versa.