Django 1.5 AbstractBaseUser with char primary key not JSON serializable

Question

I am having the following custom user model trying to use the Django 1.5 AbstractBaseUser:

class Merchant(AbstractBaseUser): 
    email = models.EmailField()
    company_name = models.CharField(max_length=256)
    website = models.URLField()
    description = models.TextField(blank=True)
    api_key = models.CharField(blank=True, max_length=256, primary_key=True)   

    USERNAME_FIELD = 'email' 
    REQUIRED_FIELDS = ['email','website']


   class Meta:
        verbose_name = _('Merchant')
        verbose_name_plural = _('Merchants')

   def __unicode__(self):
        return self.company_name 

The model works perfectly and database is as expected, but the problem is when I try to dumpdata to create fixtures for my tests.

python manage.py dumpdata --natural --exclude=contenttypes --exclude=auth.permission --indent=4 > fixtures/initial_data.json

Then I get the error:

CommandError: Unable to serialize database: <Merchant: Test Shop> is not JSON serializable

Do you have ideas what could be the reason for this. Could it be the charfield primary key or something with the abstractbaseuser model?

Thanks

Answer 1

After some time spend I found the problem. Actually it was not in Merchant model but in Product that has foreign key to Merchant:

class Product(models.Model):
    name = models.CharField(max_length=200)
    #merchant = models.ForeignKey(Merchant, to_field='api_key')
    merchant = models.ForeignKey(Merchant)
    url = models.URLField(max_length = 2000)  
    description = models.TextField(blank=True) 
    client_product_id = models.CharField(max_length='100')

    objects = ProductManager() 
    class Meta:
        verbose_name = 'Product'
        verbose_name_plural = 'Products' 
        unique_together = ('merchant', 'client_product_id',) 

    def __unicode__(self):
        return self.name 

    def natural_key(self):
        return (self.merchant, self.client_product_id) 

the natural_key method in the model returned self.merchant instead of self.merchant_id so it was trying to serialize the whole merchant object to create a natural key. After switching the natural_key method to the following one the problem was fixed:

def natural_key(self):
    return (self.merchant_id, self.client_product_id)