Edit or delete committee members leaves orphaned records in fedora

[val99erie]

Steps to reproduce the problem:

• In the rails console, create an Etd record with committee chairs and members:

cm_attrs = [
  { name: ['Frodo'], affiliation: ['Emory University'] },
  { name: ['Bilbo'], affiliation: ['University of Bilbo'] }
]

cc_attrs = [
  { name: ['Gandalf'], affiliation: ['Emory University'] }
]

etd = Etd.new(title: ['ETD 1'], committee_members_attributes: cm_attrs, committee_chair_attributes: cc_attrs)

etd.save!

• Look at the Etd record in the fedora console.

• Notice that the committee chair is correctly listed in the ths predicate, and the committee members are correctly listed in the rev predicate.

• Scroll to the bottom of the page to the 'Other Resources' section, and notice 3 nested records (1 for the chair and 2 for the members).

• So far, everything is correct in fedora.

• Now go back to the rails console and delete the 2 committee members:

etd.committee_members = nil
etd.save!

• Go back to the fedora console, and reload the page.

• Notice that the rev predicate has disappeared from the record (as expected).

• But down in the 'Other Resources' section, you still see 3 child resources, even though you would expect to see only 1.

Expected Result:

The 2 child resources should have been removed from the work's record in fedora.

Actual Result:

The 2 (orphaned) child resources still exist in fedora.

[val99erie]

Here's another clue:

If I try to delete an individual committee member with committee_member.destroy, it returns true, but the committee member didn't actually get deleted.

I stepped through the code and saw a transaction rollback:
<RDF::Transaction::TransactionError: Error merging transaction. Repository has changed during transaction time.>

I asked @no-reply about it, and he suspects that the parent work's committee_members field got updated during the middle of the transaction to update the nested record, so the transaction rolled back.