enumeratum

scala> import enumeratum._
scala> import cats.syntax.either._
scala> import io.circe._
scala> import io.circe.syntax._

scala> sealed trait ShirtSize extends EnumEntry
scala> case object ShirtSize extends Enum[ShirtSize] with CirceEnum[ShirtSize] {
   |  case object Small  extends ShirtSize
   |  case object Medium extends ShirtSize
   |  case object Large  extends ShirtSize
   |  val values = findValues
   | }

scala> val size: ShirtSize = ShirtSize.Small

scala> size.asJson
res0: Json = "Small"

scala> Json.fromString("Large").as[ShirtSize]
res1: Decoder.Result[ShirtSize] = Right(Large)


scala> Json.fromString("XLarge").as[ShirtSize]
res2: Decoder.Result[ShirtSize] = Left(DecodingFailure('XLarge' is not a member of enum ShirtSize, List()))