Class A has a field of type B (custom class). In jdo file the field is marked to be mapped via join table (despite the 1:1 relationship). When detaching A, field of type B is NOT detached. The reason is that the "<join/>" flag in the jdo file somehow prevents that from happening. No error message is shown.

I understand that there is no need to have the join table for a 1:1 relationship between 2 classes. But developers may choose to do this in case they consider changing to a 1:n relationship later and want to avoid to change the database structure.

In case it is decide not to fix this issue, there should be an exception thrown instead so that users are aware that detaching does not work in this scenario.

Test case attached. Reproduce error as follows: (1) Create database, (2) Run schema tool, (3) Run Main.java with user input "1" to set up test rows, (4) Run with user input "2" to illustrate this scenario.