This is because it's permissible to send DOI deposit files without a parent work DOI, e.g. if the only purpose of the submission is to register the chapter DOIs. But if a work has no DOI and also no chapters, we don't flag this, but instead create a DOI deposit file that doesn't contain any DOIs (hence does nothing).
Crossref will happily accept this file, and send a confirmation email which doesn't indicate any failures, just has an empty record_count (as below).
While compiling Crossref DOI deposit output, if a work has no DOI, we only raise an error if it's a chapter, not the parent work.
https://github.com/thoth-pub/thoth/blob/6532713b89fd36ed734164c058d8aef175938da0/thoth-export-server/src/xml/doideposit_crossref.rs#L437-L444
This is because it's permissible to send DOI deposit files without a parent work DOI, e.g. if the only purpose of the submission is to register the chapter DOIs. But if a work has no DOI and also no chapters, we don't flag this, but instead create a DOI deposit file that doesn't contain any DOIs (hence does nothing).
Crossref will happily accept this file, and send a confirmation email which doesn't indicate any failures, just has an empty
record_count
(as below).Relevant to #551.