problem with lua_newthread, setfenv and modules

[Graham Wakefield <lists@...>]

Hi,

I have an application in which lua scripts may be loaded by the user.  
Each script is given a 'child' lua_State created by lua_newthread().  
Keeping each table's variables separate is beneficial to the  
application, so the child state is given a local environment, with a  
metatable __index to the master globals, like this:

		lua_State *Ls = lua_newthread(L);
		
		// Create a local environment with a link to global environment via  
__index metamethod
		// this means that script variables are not shared between scripts
		lua_pushthread(Ls);
			lua_newtable( Ls );
				lua_pushvalue( Ls, -1 );
				lua_setmetatable( Ls, -2 ); //Set itself as metatable
				lua_pushvalue( Ls, LUA_GLOBALSINDEX );
				lua_setfield( Ls, -2, "__index" );
			lua_setfenv( Ls, -2 );
		lua_pop(Ls, 1);

A user script can load a module using require (e.g. require "lfs"),  
which works as normal. However, if a second script is loaded, the  
global 'lfs' is not accessible to the second script.

script 1:

require "lfs"
print(lfs) -- table (0x....)

script 2:

require "lfs"
print(lfs) -- nil
print(package.loaded.lfs) -- table (0x...)

I can't quite figure out why the second script doesn't get global  
access to the module. I wonder if the require() call is pushing the  
module as a global into script 1's environment, rather than the  
master state. Is this the case?  [in fact, does lua_setfenv() on a  
lua_State do the same as lua_replace(Ls, LUA_GLOBALSINDEX)?]

Is there a known workaround?

Thanks,

Graham