HashMaps are inconsistently decoded into Objects/Maps

[ntr-808]

When the decoder encounters a HashMap keyed by integers it (correctly) decodes them into a JS Map, however the same field where the map is empty is decoded into a regular JS Object causing interfacing code to error unless it handles both cases.

Is there a way to mark a field to be explicitly always a Map/Object?

Test data and MRE coming soon, just thought I would begin the process...