[Jython-dev] fix to put python imports before java

[Charlie G. <cha...@gm...>]

Hi,

Bugs 1421812 and 1246413 both look like they stem from the java import
mechanism being called before the python importers since it was put on
meta_path as part of the new PEP 302 system.  In 1421812 Samuele has a
nice summary of the problem where he suggests either putting the
python importer before the java importer on the meta_path or having
the java importer be in a separate entry point that gets applied after
everything else.  The Open Issues section of PEP 302 it mentions that
they don't have a mechanism to run hooks after sys.path is processed.
They suggest adding a "cookie" to the end of sys.path that triggers a
special import hook after everything else has had a chance to try to
import an entry.  That sounded exactly like the second option Samuele
mentioned and it had the nice benefit of not pushing the java importer
off into a special case.  So in the attached patch I've appended a
"__classpath__" entry to sys.path and switched the JavaImporter from
meta path to a path hook.  It only comes into effect on the path
"__classpath__".  It passes the new bug test I added for when the bad
java imports come into play, and doesn't cause any new failures in the
existing tests.

Does this sound like an adequate solution?

Charlie