Reference to abstract class tries to get 'id_field' of abstract class

[mwstobo]

When you create a ReferenceField with an abstract class as an argument, it checks for the id_field in the meta dictionary of the abstract class itself, not the inherited class.

For example:

class A(Document):
    val1 = StringField()

    meta = {
        "abstract": True
    }

class B(A):
    val2 = StringField()

class C(Document):
    val3 = ReferenceField(A)

Trying to save an instance of C with an instance of B as val3 will raise a KeyError exception on line 945 of mongoengine/fields.py.

[amcgregor]

I'm running into this when attempting to isolate common model components, such as extracting the fields and methods for a tree taxonomy schema, something I'd like to re-use. (In my case the ReferenceFields are actually in the abstract base, but they refer to 'self'.)

[david-alm]

Looks to me like this doesn't apply to LazyReferenceFields

from mongoengine import *

class Base(Document):
    meta = {"abstract": True, "allow_inheritance": True}

class Child(Base):
    field = LazyReferenceField(Base)

Saving the Child object triggers a KeyError: id_field, though it works with a regular ReferenceField

[bagerard]

@david-alm Please open another ticket and reference this one