On Tue, Jun 12, 2012 at 8:49 AM, Luke Plant <l.plant...@cantab.net> wrote:
>
> I agree my existing program had a bug. I had simplejson installed
> because a dependency pulled it in (which means it can be difficult to
> get rid of).
>
> The thing I was flagging up was that the release notes say "You can
> safely change any use of django.utils.simplejson to json." I'm just
> saying the two differences I've found probably warrant at least some
> documentation.
>
> The second issue is difficult to argue as a bug in my program or
> dependencies. Django has moved from a providing a JSONEncoder object
> that supported a certain keyword argument to one that doesn't. We could
> 'fix' it to some extent:
>
> class DjangoJSONEncoder(json.JSONEncoder):
> def __init__(self, *args, **kwargs):
> kwargs.pop('namedtuple_as_object')
> super(DjangoJSONEncoder, self).__init__(*args, **kwargs)
>
> But like that, it would create more problems if the json module ever
> gained that keyword argument in the future.
>
Like loads(), json.JSONEncoder is just an alias for
simplejson.JSONEncoder, and we need to support versions of simplejson
down to 1.9 which is what python 2.6 ships with. This
'namedtuple_as_object' thing seems to only appear as of simplejson
2.2, which means that depending on it is a bug that appears on any
system without a recent version of simplejson (for example, the
version that was bundled with Django doesn't support it). Depending on
this kwarg is a bug in Django, and should be fixed.
https://github.com/simplejson/simplejson/blob/namedtuple-object-gh6/simplejson/encoder.py
It's clear that people have begun to depend on the quirky ways in
which simplejson diverged from its earlier codebase. I found the place
where that unicode "proper behavior" was fixed, so apparently in
Python's stdlib they undid the C optimizations at some point. So I was
incorrect earlier, and the C speedups work "properly" with Python
stdlib's patch.
http://bugs.python.org/issue11982
Basically, anyone who depended on features of simplejson added after
1.9, or its wonky optimizations, already had arguably broken code in
that it only worked when simplejson is installed. I'm torn as to
whether we should add a note about these subtle problems when
switching to json, recommend that people switch to simplejson instead,
or undeprecate django.utils.simplejson as a necessary wart (we can
still stop vendoring simplejson though).
Best,
Alex Ogier
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