Conditionally enable module loading by default

Enabling module loading by default doesn't work when there are multiple
Lua modules because the symbols collide with each other when loaded with
RTLD_GLOBAL.
Make the default use of the dlopenflags conditional on there only being
one available Lua module.

lupa/__init__.py

@@ -51,10 +51,13 @@ def _import_newest_lib():
  # prefer Lua over LuaJIT and high versions over low versions.
  module_name = max(modules, key=lambda m: (m[1] == 'lua', tuple(map(int, m[2] or '0'))))
 
- # We need to enable global symbol visibility for lupa in order to
- # support binary module loading in Lua. If we can enable it here, we
- # do it temporarily.
- with eager_global_linking():
+ # Allowing module loading using dlopenflags by default doesn't work when there are multiple
+ # Lua modules because the symbols collide with each other when loaded with RTLD_GLOBAL.
+ # Enable this by default only if there is exactly one lua module available.
+ if len(modules) == 1:
+ with allow_lua_module_loading():
+ _newest_lib = __import__(module_name[0], level=1, fromlist="*", globals=globals())
+ else:
  _newest_lib = __import__(module_name[0], level=1, fromlist="*", globals=globals())
 
  return _newest_lib