JsonCodec.jsonDecoder does not seem to work with schemas derived from case classes with more than 22 fields

[stanislav-chetvertkov]

JsonCodec.jsonDecoder does not seem to work with schemas derived from case classes with more than 22 fields, in the following example

import zio.Scope
import zio.json.JsonDecoder
import zio.schema.codec.JsonCodec
import zio.schema.{DeriveSchema, Schema}
import zio.test._

import scala.annotation.nowarn

@nowarn("msg=missing interpolator")
object F22Spec extends ZIOSpecDefault {

  case class Example(
    f1: Option[String],
    f2: Option[String] = None,
    f3: Option[String] = None,
    f4: Option[String] = None,
    f5: Option[String] = None,
    f6: Option[String] = None,
    f7: Option[String] = None,
    f8: Option[String] = None,
    f9: Option[String] = None,
    f10: Option[String] = None,
    f11: Option[String] = None,
    f12: Option[String] = None,
    f13: Option[String] = None,
    f14: Option[String] = None,
    f15: Option[String] = None,
    f16: Option[String] = None,
    f17: Option[String] = None,
    f18: Option[String] = None,
    f19: Option[String] = None,
    f20: Option[String] = None,
    f21: Option[String] = None,
    f22: Option[String] = None,
//    f23: Option[String] = None
                        )

  implicit val exampleSchema: Schema[Example] = DeriveSchema.gen[Example]

  override def spec: Spec[TestEnvironment with Scope, Any] = {
    suite("F22")(
      test("should work with more than 22 fields") {
        import zio.json.yaml.DecoderYamlOps

        implicit val decoder: JsonDecoder[Example] = JsonCodec.jsonDecoder(exampleSchema)

        val string = """f1: test"""

        string.fromYaml[Example] match {
          case Left(error) =>
            TestResult(TestArrow.make(_ => TestTrace.fail(ErrorMessage.text(error))))
          case Right(value) =>
            print(value)
            assertTrue(true)
        }
      }
    )
  }
}

It returns Example(Some(test),None,None,None,None,None,None,None,None,None,None,None,None,None,None,None,None,None,None,None,None,None)

but when I uncomment f23: Option[String] = None I get (Field f2 is missing) error It could be due to some inconsistencies handling CaseClass22 and GenericRecord (for 23 or more fields) schemas

[stanislav-chetvertkov]

the same behaviour also appears when using

import zio.json.DecoderOps
...
string.fromJson[Example]

I was able to make it work by changing recordDecoder method in zio.schema.codec.JsonCodec to look like this

    private def recordDecoder[Z](structure: Seq[Schema.Field[Z, _]]): ZJsonDecoder[ListMap[String, Any]] = {
      (trace: List[JsonError], in: RetractReader) => {
        val builder: ChunkBuilder[(String, Any)] = zio.ChunkBuilder.make[(String, Any)](structure.size)
        Lexer.char(trace, in, '{')
        if (Lexer.firstField(trace, in)) {
          while ( {
            val field = Lexer.string(trace, in).toString
            structure.find(_.name == field) match {
              case Some(Schema.Field(label, schema, _, _, _, _)) =>
                val trace_ = JsonError.ObjectAccess(label) :: trace
                Lexer.char(trace_, in, ':')
                val value = schemaDecoder(schema).unsafeDecode(trace_, in)
                builder += ((JsonFieldDecoder.string.unsafeDecodeField(trace_, label), value))
              case None =>
                Lexer.char(trace, in, ':')
                Lexer.skipValue(trace, in)

            }
            (Lexer.nextField(trace, in))
          }) {
            ()
          }
        }
        val tuples = builder.result()
        val collectedFields: Set[String] = tuples.map { case (fieldName, _) => fieldName }.toSet
        val resultBuilder = ListMap.newBuilder[String, Any]

        // add fields with default values if they are not present in the JSON
        structure.foreach { field =>
          if (!collectedFields.contains(field.name)) {
            val value = field.name -> field.defaultValue.get
            resultBuilder += value
          }
        }
        (resultBuilder ++= tuples).result()
      }
    }

so that it adds fields with their default values from the schema if they were not present in the input JSON

I'm going create a pr containing the change soon