On Tue, Oct 23, 2012 at 5:11 PM, Russell Keith-Magee <
russ...@keith-magee.com> wrote:
>
>
> On Tue, Oct 23, 2012 at 6:52 PM, Andrew Ingram <andrewof...@gmail.com>wrote:
>
>> Hi all,
>>
>> This one stung me today. Basically as part of an event (calendar) app, I
>> have functionality for splitting a series of events into two at a given
>> timestamp. The details aren't particularly relevant, but the key thing is
>> that I had a method called "split" on one of the models.
>>
>> This was working fine until I tried to add a ManyToManyField to the same
>> model, at which point it through a rather ugly error during initialisation
>> of the apps.
>>
>> django/db/models/fields/related.py line 56, in add_lazy_relation
>>> app_label, model_name = relation.split(".")
>>> TypeError: unbound method split() must be called with RecurringEvent
>>> instance as first argument (got str instance instead)
>>
>>
>> Because I had no knowledge of the inner workings here, this error wasn't
>> helpful until pdb told me that `relation` was an instance of my model. The
>> issue is that in this point in the code, relation can either be a model or
>> a string 'app_label.model_name', so it's using the presence of a split
>> function to determine which it is, me having a split function on my model
>> breaks this check. Having a non-callable 'split' causes a similar problem,
>> just with a different exception.
>>
>> Long story short, adding a 'split' method to my model caused the
>> inner-workings of Django to break, I think the documentation should provide
>> a list of attribute names that can't be added to a Django model without
>> breaking things, though this is the first time I've ever come across such a
>> problem so it might be a one-off.
>>
>> Hi Andrew,
>
> Thanks for that gnarly bug report. I'm a little surprised that the 'split'
> name causes a problem here; based on my knowledge of Django's internals, I
> wouldn't have thought that the situation you describe shouldn't be a
> problem. My gut reaction tells me that the actual problem is somewhere else
> in your model definition, causing the wrong object instance to be passed
> into the 'relation' variable; the 'split' method is a symptom, rather than
> the actual problem. However, I may be wrong.
>
> If you can open a bug report with a complete working (or rather, broken)
> example of the problem, we can dig into it more. If you're right that the
> split method is the problem, we should certainly document it; if the
> problem lies somewhere else, there's possibly some better validation that
> we need to do.
>
> Yours,
> Russ Magee %-)
>
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No this is a bug in Django, I see it.
https://github.com/django/django/blob/master/django/db/models/fields/related.py#L51
Basically some genius (very likely me), decided we shouldn't type check for
string or model, and just try to call split.
It's an easy enough fix. Please file a bug and if there's no patch I'll do
it tonight.
Alex
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