It is not allowed to specify the scala Map type when using proto3 maps

[franbh]

It would be great if ScalaPB allowed us to specify which type of scala Map is going to be used when declaring proto3 maps. Right now, it is restricted to scala.collection.immutable.Map, but sometimes it is better to use mutable Maps.
Namely, I'm thinking about an option like this:
map<string, string> my_map = 1 (scalapb.field).map_type = "scala.collection.mutable.Map"

WDYT?

[thesamet]

It makes sense to add this. Can you work on a PR? It would be worth exploring if (scalapb.field).collection_type could be used for this rather than adding map_type.

[franbh]

Sure, I'll try to find some free time and look into it.

[ollyw]

Any progress on support for this? I have a similar use case that I would really like to be able to specify (scalapb.field).collection_type = "scala.collection.immutable.SortedMap"