Issue #3060 resolved
delete/insert into update doesn't handle relationship changes
New object with the same ID as existing one implicitly merged via cascade rules has old value of relationship property after the commit when the new value is None.
doc.doc_links = [DocLink(id=doc_link_id, link=None)] session.commit() assert doc.doc_links.link is None # fails
Full test is attached (test3 is the test case that fails).