Gaps between Jython and Django
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To run Django on Jython, with a PostgreSQL backend, the following steps are necessary:
Use the [https://jython.svn.sourceforge.net/svnroot/jython/branches/modern/ Modern branch] of Jython. This consolidated the bugs, workarounds, and patches found below -- plus a bunch more -- in a stable, almost-ready-to-be-merged-into-trunk version of Jython. The most important aspect is that we have tried to make Jython conform more to CPython, using Django as our guide, although there are some gaps - especially if Django already had incorporated fixes. Our driving goal is to converge on these gaps over time.
- Use the Django trunk (tested with rev 6992, later should be OK too).
Apply these two patches, [https://jython.svn.sourceforge.net/svnroot/jython/trunk/sandbox/jbaker/django/dispatch/robustapply.py django.dispatch.robustapply] ([https://hg.leosoto.com/django.jythonport/rev/bb2b9048ed14f72e99c5c133c7ecaaeb0a5c425c diff]) and [https://jython.svn.sourceforge.net/svnroot/jython/trunk/sandbox/jbaker/django/views/debug.py django.views.debug] ([https://hg.leosoto.com/django.jythonport/rev/663bcf5efc31409899fcdc10009bc92df3e1f6b9 diff]) due to Leo Soto. These should be in Django trunk soon.
- Copy these three files from CPythonLib to Lib: gettext.py, locale.py, optparse.py. Please note that these files are only partially working on Jython, that's why they haven't been promoted yet (gettext.py actually works, as verified by test_gettext.py, but depends on still failing locale.py). But they are very close, and they appear to be fine for Django. Certainly fine for this round of development!
Use the backend [https://jython.svn.sourceforge.net/svnroot/jython/trunk/sandbox/jbaker/django/db/backends/postgresql_zxjdbc/ zxjdbc_postgresql], which was contributed by Leo Soto.
Here's what works:
syncdb and the very cool Django admin run; many unit tests pass. You can run with internationalization enabled. You do need to run the dev server with --noreload for now. We need to document here how to run with [http://www.xhaus.com/modjy/ modjy], which is Alan Kennedy's servlet container for WSGI apps.
In running the model unit tests, here are the things we seem to be missing, accounting for most of the approximately 75 failures:
Many doctests are fragile, because they depend on the dict traversal ordering; in Jython, this is different that CPython, and if we adopt ConcurrentHashMap, it's not even repeatable. This is a pervasive bug in Django.
* We still have some encoding problems, again seen in doctests. An example where output is expected to be lower case hex, not upper case. I fixed the problem in PyUnicode, but there are more places.
Problem with the ManagerDescriptor handling, in django.db.models.manager.
- No decorators yet! (But they are coming soon, even available experimentally for Jython.)
There may be some other rough categories, we need to look at the failures more systematically. All that doctest noise is certainly annoying!
Former Major problems
(Preserved to show how much we had to go through...)
Jython does not support non-str keys in __dict__ right now. Jim Baker replaced the custom dictionary in PyStringMap with a HashMap (along Groves' earlier work). This change should resolve this problem. Try the [https://jython.svn.sourceforge.net/svnroot/jython/branches/modern/ modern] branch. Problem encountered in django/utils/_threading_local.py.
Something goes wrong with re.compile(u"([\u0080-\uffff])") in django/utils/text.py I think it is a lacking in our array implementation but this needs more investigation.
django/views/debug.py wants to know a function's __module__. functions don't have a __module__ attribute in jython yet. [http://sourceforge.net/tracker/index.php?func=detail&aid=1800472&group_id=12867&atid=312867 patch]
inspect.getargs() doesn't work.
That's because co_code isn't supported by PyTableCode.
But, co_code is used by getargs() only to discover anonymous tuple arguments. Commenting such section seems to be enough to get the other cases working.
workaround [https://dev.archer.edu.au/projects/kepler/svn/jython-django/trunk/jython-patches/co_code-workaround.patch patch]. just sets co_code = "". i haven't come across any problems for this inside django yet, but i'm sure it'll break other python code -- TristanKing
time module lacks strptime().
workaround [https://dev.archer.edu.au/projects/kepler/svn/jython-django/trunk/jython-patches/time-strptime.patch patch]. this is incomplete, untested, and not optimal but works for the django tutorial -- TristanKing
inspect.isclass(time) shouldn't return True [http://sourceforge.net/tracker/index.php?func=detail&aid=1786009&group_id=12867&atid=112867 bug]
Django [http://code.djangoproject.com/changeset/6194 works around this] until it's fixed.
Former Minor annoyances
slice should be a type, not a function. [http://sourceforge.net/tracker/index.php?func=detail&aid=1791931&group_id=12867&atid=112867 bug] [http://sourceforge.net/tracker/index.php?func=detail&aid=1798544&group_id=12867&atid=312867 patch]
PyBoolean.__tojava__ returns an Integer
It affects zxJDBC unless a DataHandler sets the right type of boolean parameters. Fortunately, JDBC30DataHandler does this thing, at least on my limited tests -- LeonardoSoto
Jython does not have __builtins__ as a module. Django adds "_" as a convenience method for calling gettext in django/conf/__init__.py.
According to the Python docs, __builtins__ is a implementation detail and shouldn't be used by portable applications, so it's a Django problem. (See note about __builtins__ here: http://docs.python.org/ref/naming.html)
Jython methods are not descriptors. It seems a implementation detail. [http://code.djangoproject.com/ticket/5664 django patch]
Jython classes which extend dict cannot be compared to a dict. [https://sourceforge.net/tracker/index.php?func=detail&aid=1804011&group_id=12867&atid=112867 bug] [https://dev.archer.edu.au/projects/kepler/changeset/149?format=diff&new=149 django patch]
Jython doesn't recognize __unicode__ methods assigned to instances.
But, this is the only __*__ method where CPython allows this, and it's not documented anywhere. So, it's a implementation detail and should be fixed on Django. [http://code.djangoproject.com/ticket/5560 django patch]
Already Fixed
(And many more!)
Jython does not have sys.stdout.isatty. Jython should get added to the exclusions around that call in django/core/management.py (win32 and 'Pocket PC' are already excluded).
Fixed in [http://code.djangoproject.com/changeset/6032 Django changeset 6032]
stringmap (or the __dict__ implementation) needs a pop(o) method.
Jython lists and tuples don't have __iter__ .
Fixed in [http://code.djangoproject.com/changeset/6211 Django changeset 6211]
Jython does not have os.getpid().
- Django workarounds it now.
Jython does not have os.W_OK needed in django/core/management.py. This probably will not be hard to add this since java.io.File has a canWrite().
os.chmod should be implemented too (After checking for write permissions, Django will try to change them if necessary).
- That's hard. Maybe Django shouldn't check for permissions if running on Jython.
- Django don't check or change file permissions when running on Jython now
The U (Universal newlines) flag for open() isn't recognized on Jython
- Unicode string interpolation doesn't work
object has a __unicode__ attribute (it doesn't on CPython) [https://sourceforge.net/tracker/?func=detail&atid=112867&aid=1800378&group_id=12867 bug] [https://sourceforge.net/tracker/?func=detail&atid=312867&aid=1800381&group_id=12867 patch] -- TristanKing
metaclasses need to know the __module__ of its classes [http://sourceforge.net/tracker/index.php?func=detail&aid=1781500&group_id=12867&atid=112867 bug] [http://sourceforge.net/tracker/index.php?func=detail&aid=1789137&group_id=12867&atid=312867 patch]