[SOLVED] How to generate any protobuf Enum as String with only one TypeMapper?

How to generate any protobuf Enum as String with only one TypeMapper?

For instance, I have some enums in my proto schema:

enum E1 {
     UNKNOWN = 0;
     OPTION_1 = 1;
     OPTION_2 = 2;
     OPTION_3 = 3;
}

enum E2 {
     UNKNOWN = 0;
     ANOTHER_OPTION_1 = 1;
     ANOTHER_OPTION_2 = 2;
     ANOTHER_OPTION_3 = 3;
}

message M {
    E1 my_enum_1 = 1;
    E2 my_enum_2 = 2;
}

I can generate scala classes with strings instead of enums by providing scalaPB TypeMappers:

TypeMapper(_.name)(E1.fromName(_).get)
TypeMapper(_.name)(E2.fromName(_).get)

But I don't want to copypaste same TypeMappers for any single Enum

Is there any way to make only one TypeMapper for all enums with scalaPB?

Solution

Yes, this can be done.

If you want to make ScalaPB use String for all enums within a package, you can add package-scoped options file to tell ScalaPB to set the scala-type for each enum to a String using field transformations:

// options.proto:
syntax = "proto3";

import "scalapb/scalapb.proto";

option (scalapb.options) = {
  scope: PACKAGE,
  field_transformations : [
    {
      when : {
        type: TYPE_ENUM
      }
      set : {[scalapb.field] {type : 'String'}}
    }
}

The next step will be to define a typemapper for all enums. Borrowing from Ivan's answer, this could be defined as follows:

implicit def enumMapper[E <: GeneratedEnum](implicit ec: GeneratedEnumCompanion[E]) =
  TypeMapper[E, String](_.name)(ec.fromName(_).get)

If the above code is added to a package object in the same package as the generated code, or imported using the import option in ScalaPB, the typemapper will be found in implicit search.