Checking iterables by looking for a __iter__ attribute doesn't work on Jython

[leosoto <leo.soto@…>]

Jython list and tuples are iterables but don't have iter, so are incorrectly detected as non-iterables by model validation.

[leosoto <leo.soto@…>]

Replaced iter attribute lookup by trial an error with iter()

[leosoto <leo.soto@…>]

added a missing header on the diff file

[Malcolm Tredinnick]

I'm not in love with the implementation. A couple of comments:

• you create _is_iterable in validation.py and then later on do almost the exact same thing in test/client.py. Why not create a file in django/utils/ called something appropriate (or use itercompat.py, which we already have) and put a utility function in there?
• Does Jython have a basestring type? We use isinstance(foo, basestring) all over the place in Django, so it'd be nice we could also use that here instead of types.StringType. Otherwise there are a lot of places you're going to have to change.

[leosoto <leo.soto@…>]

another patch following malcom's suggestions

[Fredrik Lundh <fredrik@…>]

Looks reasonable. Not sure about the name "itercompat", though. CPython does not guarantee that all iterables have an iter method; they may just implement the tp_iter slot on the C level, or just provide a C-level sequence API. iter() handles all those cases.

[Fredrik Lundh <fredrik@…>]

(oh, sorry, missed that itercompat.py is an existing module. +1 from me, then)

[leosoto <leo.soto@…>]

Uses is_iterable on django.template too. Also changes the order of the typical check for the common case: now we first check for non-strings, next for iterables.

[leosoto <leo.soto@…>]

The previous patch file is messed up. Now it's OK.

[Fredrik Lundh <fredrik@…>]

Looks good to me. If you've missed something else, we can deal with that in an additional issue. Boldly tagging this and marking it as "Read for checkin".

[Jacob]

(In [6211]) Fixed #5445: added some compatibility code for the lack of iter in Jython 2.2. Thanks, Leo Soto.