Lua 5.2 environments and changing a loaded file environment

[Patrick Donnelly <batrick@...>]

Hello List,

I'm trying to decide how best to change the environment of a loaded
"script" file such that it can be given a brand new environment and
re-executed multiple times without recompiling the script (loadin).
Obviously the most straightforward method would be to do something
like:

local f = assert(loadfile(file))
while true do
  -- ...
  debug.setupvalue(f, 1, {})
  f()
  -- ...
end

However, this actually won't work because the f closure will "share"
the upvalue across invocations. Closures created by the first
invocation will use the new table set for the second invocation as
their _ENV. (One could use debug.upvaluejoin to give it a new upvalue,
but this is an even worse hack in my opinion.)

I would rather avoid changing the file any to accomplish this (it
messes with debug output from errors and whatnot) -- that is, I don't
want to add a function to each script that lets me change the
environment dynamically. Does anyone see a better way to do this?

-- 
- Patrick Donnelly