Protobuf conversion bug

[gafiatulin]

It appears that at some point during conversion to protobuf entity-builder instance cache is used, but it looks like builders are mutable and are not reset to initial clean state which leads to incorrect results.

Reproduction (click to expand):

Given
definition.proto:

syntax = "proto3";

message DataEntryPb {
  string key = 1;
  string value = 2;
}

message EntityPb {
  string entityId = 1;
  repeated DataEntryPb metadata = 2;
}

message MultiEntityPb {
  string multiEntityId = 1;
  repeated EntityPb entities = 2;
}

and
Reproduction.scala:

import magnolify.protobuf._

object Reproduction extends App{

  final case class DataEntry(key: String, value: String)
  final case class Entity(entityId: String, metadata: Seq[DataEntry])
  final case class MultiEntity(multiEntityId: String, entities: Seq[Entity])

  val me = MultiEntity(
    "me1",
    Seq(
      Entity("entity1", Seq(DataEntry("key1", "value1"))),
      Entity("entity2", Seq.empty),
    ),
  )

  val pbType = ProtobufType[MultiEntity, Definition.MultiEntityPb]


  val x = pbType.to(me)

  println(x)
}

Produces the following:

multiEntityId: "me1"
entities {
  entityId: "entity1"
  metadata {
    key: "key1"
    value: "value1"
  }
}
entities {
  entityId: "entity2"
  metadata {
    key: "key1"
    value: "value1"
  }
}

Note that metadata is supposed to be empty for the second entity.