Re: Simulating getfenv for Lua 5.2

[Roberto Ierusalimschy <roberto@...>]

> We're considering moving to Lua 5.2 upon release. While it's looking
> promising, the biggest hurdle for us is the abolition of getfenv.
> 
> We're using getfenv to simulate Python's package system, such that:
> 
> import 'hello.world'
> 
> imports a lua file into the variable 'world' of _this_ environment.

If 'import' is only called from the main function in a module, then you
can safely assume that the environment will be the first upvalue of the
callee function. So, you can use debug.getupvalue to get its value:

  function import(fname)
      ...
      local this_env = {}
      loadin(fname, this_env)
      local _, calling_env = debug.getupvalue(debug.getinfo(2).func, 1)
      assert(_ == "_ENV")
      calling_env['world'] = this_env
  end

(Untested code...)

-- Roberto