Saxon

Interesting idea, but it's not easy. Items other than nodes (for example integers or strings) don't have individual identity, so they aren't readily traceable back to a location in a JSON file.

We do however have a mechanism in XPath 4.0 (based on experimental features implemented as Saxon extensions) whereby any XDM item can be labelled to indicate its provenance. We could consider an option on json-doc() that causes items to be labelled with location information. We would also need to enhance the JSON parser to maintain such information but that is do-able in principle.

As it happens I'm working on the JSON parser at the moment, so it's a good time to be thinking about such requirements.