Indeed, I can confirm that this is a bug in the current implementation. We also noticed that when implementing contributions, but just added corresponding comments in the fs_task_contrib branch, yet without a ticket nor fixing it. From the tests I've made, I think this is an issue for several models, not just Test.

It seems to be a bug in Rails. The corresponding issue (rails/#20676) was opened in 2015. There are multiple workarounds:

• our existing unique_xml_id validation for TaskFiles seems to work fine (since it works with the objects)
• monkeypatch the uniqueness validator
• create a (kind of) generic validator for that problem (accepts_nested_attributes_for breaks the uniqueness with scope validation rails/rails#20676 (comment))
• create the correct database constraints (!) and use a gem that converts a database constraint exceptions to a validation message (https://github.com/toptal/database_validations)

As far as I understand the issue, it only affects objects that are saved through nested_attributes. Since we are only using nested_attributes for ModelSolutions, Tests and TaskFiles and the TaskFiles need a specific validator anyway, we only need to find a solution for Tests and ModelSolutions.

I suggest we add the necessary database constraints and a validator that we can use for both models.

Yes, that sounds good.

I'm not able to reproduce this bug currently. It may have gotten fixed by #1103 and the added ParentValidation.

I just tested on the latest main branch (commit 5a9d6d3) and was able to reproduce the issue. Below is a reproduction video.

Ah I misunderstood and created TaskFiles instead of Tests with the same id. Thanks!