Cannot reset ForeignKeyField to None

[orsinium]

import peewee

class A(peewee.Model):
    pass

class B(peewee.Model):
    a = peewee.ForeignKeyField(A, null=True)

b = B(a=A())

# works as expected:
b.a
# <A: None>

# unexpected:
b.a = None
b.a
# <A: None>

Expected behavior: when None is assigned to the ForeignKeyField, the field value is None.
Actual behavior: assigning None to the ForeignKeyField has no effect.

How to reset a foreign key to None?

[coleifer]

This was happening because peewee only cleared the related object reference (the A instance on B) if the actual value of the FK changed. Since it was NULL to start with (e.g. A.id is None), peewee did not register that there was anything to do. In practice I don't believe this would lead to any inconsistency in the database, but I can see how it might be confusing.

Fixed.

[orsinium]

Thank you for the answer! I think I understand now: setting b.a to None was interpreted as setting b.a.id to None, which is already true. In my application, I distinguish between "the A record is not created yet" and "there is no A record related to this B record". So you're right, it was confusing. I found a workaround, though, by implementing A.__bool__.