An issue arose on Wikidata because someone had changed the translation section IDs (<!--T:1--> and so on). It wasn't discovered until much later, and is a big mess to clean up.
I think that the extension should give users a strong warning when they mark the page for translation and the IDs have been changed, or maybe disallow it entirely. That would hopefully prevent situations like this in the future.
Version: unspecified
Severity: enhancement
Could you define "changing the translation section IDs"?
By the way, https://www.mediawiki.org/wiki/Help:Extension:Translate/Page_translation_administration#Changing_the_source_text (I think I also added this as required reading to get translation admin status, I hope bureaucrats have not been careless).
This is the definition: https://www.wikidata.org/w/index.php?title=Wikidata:Glossary&diff=3110912&oldid=2847353 :-)
Done with good intentions, of course, but it messed up everything (since I only discovered it today, and reverted, but many translations had come in in the meantime).
How can the extension know that the unit identifier was previously assigned to a unit with a different unrelevant text? The sections content can't be freezed forever.
Unless you propose a workable solution I suspect this will be a WONTFIX or INVALID.
The documentation states very clearly not to mess up with unit markers, and the most obvious requirement to assign any user right is that one should know what one does (and one's own limits)...
It's difficult, but not impossible. It can be done by checking two revisions (typically the next-latest vs. the latest, but could also be next-latest-marked-for-translation-revision vs. curent-trying-to-mark-for-translation-revision) against each other. If nothing (or very little) has changed except the translation ID, that should raise a red flag.
I don’t think saving the page should be prevented; it would make editing translatable pages even more complicated, and it’s the translation administrators’ task to make sure the translatable page guidelines are followed, not regular editors’. Maybe when marking the page for translation, deleted translation units could be listed where they used to be, instead of at the bottom of the page? This way the translation admin can more easily spot such cases, and it’s also technically relatively easy (no heuristics needed).