I'm not understanding this use case. What does it mean that a TU only has a place holder? What are we translating here? And what is this merged with ? I'm actually not understanding how XLIFF(2) filter is used. Why do we want to extract an XLIFF file, resulting in another XLIFF file, translate that second XLIFF file, then merge to make a third, merged XLIFF file ? Can someone tell me ?
Anyway, it sounds like we have two opposite goals. For leveraging, we want a more tolerant merge logic to maximize reuse of the existing translations (but we still don't want to go too far to avoid the merge result that doesn't make sense). And for this use case (although I still don't understand it), more strict merge. Maybe we need another boolean argument to satisfy both usage, or even a separate method?