While developing https://github.com/mdedetrich/scalajson I have realised that I need to create a new type of collection to satisfy the requires of a JSON Object, mainly I require an immutable map that has effectively constant lookup on all operations as well as maintaining key order.
Unfortunately there is no scala collection which satisfies this requirement which means I would have to make a new collection type (the only known current way to make such a collection is for it to be backed internally by a map + vector).
There is currently a branch in the project which implements this collection, however I realised that it would be far better design plus easier to maintain if I put this collection into its own library which I wish to call vector-map. The library would have the exact same design goals of ScalaJson (in the sense that it would have zero dependencies, be ultra stable with minimal releases and conform to all of the binary compatibility guarantees that scalajson itself has).
The implications of this would be that scalajson is no longer truely zero dependency (it would depend on vector-map). Also there are questions about whether to include VectorMap in the 2.13 collections redesigned.
An initial implementation of the library can be found here https://github.com/mdedetrich/ordered-map