inconsistent behavior of explicit primary_key and ManyToManyField

[zeliboba7@…]

In some cases explicit primary_key allows to use it for ManyToManyField relation before .save(), in others not. See example models.py:

from django.db import models

class Author(models.Model):
    name = models.CharField(maxlength=50)

class Reference(models.Model):
    """
    >>> a = Author(name='some name')
    >>> a.save()
    >>> r = Reference(title='some title')
    >>> r.authors.add(a)
    >>> r.save()
    """
    id = models.CharField(maxlength=5, primary_key=True)
    title = models.CharField(maxlength=50)
    authors = models.ManyToManyField(Author)

The doctest passed, since I specified primary_key explicitly and it works without r.save() before adding Author. but if you'll change id field to

    id = models.AutoField(primary_key=True)

or to

    id = models.IntegerField(primary_key=True)

the doctest fails. the only cure is using r.save() before before r.authors.add(a) or
r = Reference.objects.create(title='some title')
I tried both on django-0.96 and svn version with sqlite3 backend

[Jacob]

You should never be able to add objects to an M2M if either object isn't saved yet. The only reason this works at all with the CharField is that id gets set to "" (the empty string) by default. You always need to save() before added related objects.