Saving CPK in a normal PK attribute stopped working after upgrading to Rails 6.1 about composite_primary_keys

[dmke]

Turns out, there must be something else borked... I've build a reproduction, which does what it should on all Rails versions so far (5.2, 6.0, 6.1).

Sorry for the noise.

[cfis]

No worries - glad you figured it out!

[dmke]

In the end, there was a misconfiguration: We have an Inquirable module mixed which (a) got mixed in the *Inquiry classes, and (b) dynamically creates the association based on the name of the class it was mixed in (e.g. HouseInquiry → belongs_to :house, has_one :house_owner_billing etc.).

The actual problem was a double declaration of the house_owner_billing (for whatever reason; once in the mixin, once in the class itself). This didn't bother Rails < 6.1, but since 6.1 seems to be an error.