ZIO-JSON decoding with default values in case class fails for scala 3.2.2 but succeeds in 2.13.8

Question

I have a short test program that fails to decode a jsonstring because the personId is missing in the jsonstring.

However, I have a default value set in the case class for personId based on zio documentation

https://zio.dev/zio-json/decoding#automatic-derivation-and-case-class-default-field-values

What am I doing wrong here ?

import zio.*
import zio.json.*
import zio.schema.{DeriveSchema, Schema}

final case class Person(personId: Long = 1, name: String, age: Int)


object Person {
  implicit val decoder: JsonDecoder[Person] = DeriveJsonDecoder.gen[Person]
}


object MyApp extends ZIOAppDefault {

  override def run: ZIO[Environment with ZIOAppArgs, Any, Any] =
    for {
      _ <- Console.printLine("Decoding a JSON string representing a person...")
      jsonString =
        """
        {
           "name": "John",
           "age": 30
        }
        """.stripMargin
      result <- ZIO.fromEither(jsonString.fromJson[Person])
      _ <- Console.printLine(s"Decoded Person: $result")
    } yield ExitCode.success
}

Output:

Decoding a JSON string representing a person...
timestamp=2023-11-02T21:11:01.198368Z level=ERROR thread=#zio-fiber-1 message="" cause="Exception in thread "zio-fiber-4" java.lang.String: .personId(missing)
    at <empty>.MyApp.run(MyApp2.scala:25)
    at <empty>.MyApp.run(MyApp2.scala:27)"

Process finished with exit code 1

Versions:

val zioVersion            = "2.0.13"
val zioJsonVersion        = "0.5.0"

scala version 3.2.2

Answer 1

I was able to resolve this issue based on the help I got from discord community. There is a similar issue reported at https://github.com/zio/zio-json/issues/779

Solution is to set scala compiler option

-Yretain-trees