Allow parent relations to specify the related_name of a class property

[Samuel Spencer]

I can't come up with an appropriate example, so I'll use a cut back version of actual code. I'm trying to implement an ISO standard, and am using a concrete base class, with a number of relations between objects, as shown below. Unfortunately, the names of these objects and relations are defined by the spec and can't be changed without a lot of hassle.

	
class Metadata(models.Model):
    name = models.CharField(max_length=255)
	
class Property(Metadata):
    pass
	
class ObjectClass(Metadata):
    pass
	
class DataElementConcept(Metadata):
    object_class = models.ForeignKey(ObjectClass)
    property= models.ForeignKey(Property)
	

However, the system checker has a problem with this:

SystemCheckError: System check identified some issues:
	
ERRORS:
aristotle_mdr.DataElementConcept.property: (models.E006) The field 'property' clashes with the field 'property' from model 'aristotle_mdr._concept'.

What appears to happen is that DataElementConcept.property (a relation between two pieces of metadata) is clashing with MetadataItem.property (a relation from parent class to child class).

Since a parent-child relationship using inheritance is just a OneToOneField thats made by ​django.db.models.base.ModelBase it'd be nice to be able to add some details to a classes Meta field to change the related_name of the generated field, for example:

	
class Metadata(models.Model):
    name = models.CharField(max_length=255)
	
class Property(Metadata):
    class Meta:
        parent_related_name = "property_subclass"
	

and the ModelBase coude would be similar to:

                    field = OneToOneField(
                        base,
                        on_delete=CASCADE,
                        name=attr_name,
                        auto_created=True,
                        parent_link=True,
                        related_name=base._meta.parent_related_name
                    )
}}

[Simon Charette]

I'm not convinced it's worth adding a Meta option for the rare cases when this is required. Explicitly defining your parent link as you've pointed out should do.

class Property(Metadata):
    metadata_ptr = OneToOneField(
        Metadata,
        on_delete=CASCADE,
        parent_link=True,
        related_name='property_subclass',
    )

[Tim Graham]

Agreed, I think defining fields is a more clear solution than a Meta option.

[Samuel Spencer]

I didn't even realise that was possible! Cheers.