Customize ScalaPB code generation using ScalaPB transformations on protoc-gen-validate rules

CreateAccountRequest.proto

syntax = "proto2";

package teads.api;

import "validate/validate.proto";

message CreateAccountRequest {
  required string first_name = 1 [(validate.rules).string.max_len = 255];
  required string last_name = 2 [(validate.rules).string.max_len = 255];
  required string email = 3 [(validate.rules).string.email = true];
  optional string website = 4 [(validate.rules).string.uri = true];
  repeated string roles = 5 [(validate.rules).repeated = {min_items: 1, unique: true}];
}

CreateAccountRequest.scala

package teads.api

final case class CreateAccountRequest(
  firstName: String,
  lastName: String,
  email: Email,
  website: Option[URI] = None,
  roles: cats.data.NonEmptySet[String]
) extends scalapb.GeneratedMessage

transformations.proto

package teads.api;

import "scalapb/scalapb.proto";
import "scalapb/validate.proto";
import "validate/validate.proto";

option (scalapb.options) = {
  scope: PACKAGE
  field_transformations: [
    {
      when: {options: {[validate.rules] {string {email: true }}}}
      set: {[scalapb.field] {type: "teads.api.Email" }}
    },
    {
      when: {options: {[validate.rules] {string {uri: true }}}}
      set: {[scalapb.field] {type: "teads.api.URI" }}
    }
  ]
  // there are even built-in transformations for cats NonEmpty collections!
  preprocessors: ["scalapb-validate-preprocessor"]
  [scalapb.validate.file] {
    cats_transforms : true
  }
};