Hi everyone,

 
I'm working on two add-ons. In one add-on, I define an abstract model to use as a base (A), and I also define two concrete models that inherit from this base model (B and C)

In another add-on, I use the base model as a relation in another model (D). My idea was that this would display the items from the concrete models. However, I get an error when I try to create model D

class A(models.AbstractModel):
    _name = "a"

class B(models.Model):
    _name = "b"
    _inherit = "a"

class C(models.Model):
    _name = "c"
    _inherit = "a"

class D(models.Model):
    a_id = fields.Many2one("a", string="A")

The error: 

  File "/odoo/odoo/models.py", line 4045, in _read_format
    vals[name] = convert(record[name], record, use_display_name)
                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/odoo/odoo/fields.py", line 3295, in convert_to_read
    return value.id
           ^^^^^^^^
AttributeError: 'A' object has no attribute 'id'

I tried changing model A to a concrete model, and that made the error disappear. However, it doesn't show the children B and C when I try to create model D. I also tried instantiating model A when creating models B and C. In this case, it appears when I create model D, but I lose the ability to search and filter by features of models B and C.

Is this possible, or am I wrong in trying to make this relationship with the abstract model? 

Any pointers appreciated!