Multiple ManyToManyField related_name documentation

[Brandon Chinn]

I came across a bug ​the other day about having a model with multiple ManyToManyFields to the same Model. The bug occurs with the following code:

# models.py
class MyModel(models.Model):
    foo = models.ManyToManyField('other_app.OtherModel', related_name='+')
    bar = models.ManyToManyField('other_app.OtherModel', related_name='+')

# shell
>>> x = MyModel.objects.create()
>>> y = OtherModel.objects.create()
>>> x.foo.add(y)
>>> x.foo.all() # returns []

So there's no errors or anything thrown. However, accessing with the through model still works.

>>> x.foo.through.objects.all() # returns [<MyModel_othermodel object>]

I eventually found the answer in the ​Django documentation for version 1.6 saying that if you have more than one ManyToManyField pointing to the same model, you need to set the related_name to a unique value ending in +. However, this description was removed starting in the 1.7 docs. I think we need to re-add this in because it's a pretty significant specification about the ManyToManyField I would never have found, if not for a ​2012 StackOverflow post.

[Tim Graham]

I guess 82a58ce5b67e0b79fa0efbad72e21d9d1be25ceb may have been reverted prematurely on 1.7. I think it's fixed on 1.8.5+ by 0e2d3b93043676975aa921a70b5faafef02cac5c. Does that look correct?

[Brandon Chinn]

Ah yes, that works, thanks!