islandora_datastream_crud_generate_derivatives does not attach thumbnails to books and newspaper issues, because that process is not strictly part of derivative creation. We should fire islandora_paged_content_derive_thumbnail_of_parent() for books and newspaper issues when islandora_datastream_crud_generate_derivatives is run.
I think I am wrong - TNs for books and issues appear to be regenerated. I'll test compound object TNs and expand this issue or close it as appropriate.
islandora_datastream_crud_generate_derivatives
does not attach thumbnails to books and newspaper issues, because that process is not strictly part of derivative creation. We should fireislandora_paged_content_derive_thumbnail_of_parent()
for books and newspaper issues whenislandora_datastream_crud_generate_derivatives
is run.