Component used: Room
Version used: 2.4.0-alpha04
Devices/Android versions reproduced on: Pixel 3a emulator

Description:

It's not uncommon to have an id column of every database entity. However, the code generated using the new JOIN feature introduced in Room 2.4.0 doesn't have the ability to distinguish between id columns from different entities, which can produce completely wrong results.

I've attached a minimal working AS project. In this I've created a User and a UserComment Room entity and attempt to retrieve a list of all Users mapped to their UserComments. But because both entities contain an id-column, Room gets confused and actually returns a list of Users with ids taken from UserComment.

As I understand it, differentiating columns with the same name is difficult for Room, but this issue makes the new feature much less useful and downright dangerous given how prevalent the name id for the column is.

If it's not possible to fix it, perhaps the Room plugin could generate a warning or error if it picks up duplicate column names. As it stands, Room will just silently create faulty data.