Moves away from the deprecated QtScript module
Just wanted to add this: Really great work! -- I wanted to raise this issue earlier on the KF5 mailing list: ki18n was the last major framework that depended on the deprecated QtScript. Nice to see it being ported! <3
Can't really review this code either, though. I don't now enough about the QtScript/QtQML differences.
I can't say about QtScript to QtQML conversion, but wrt. those FIXMEs, removing variable argument lists obviously breaks compatibility, and especially the acall function makes no sense without it.
Note the latest patch still has a maximum number of arguments for acall. I checked all the usages, and the only place that uses acall with a variable set of arguments is the sr (Serbian) translation. Since supporting a variable number of arguments would require changes to QtDeclarative and thus mean we would need to support both models until KDE depends on Qt 5.13, perhaps it would be easier to just rewrite the serbian translations apply_to_word function?