Scala3 - nested ADTs example - Response

ResponseScala2-nodocs.scala

import scala.util.control.NonFatal

sealed trait Response[+A] {

  def returnValue: Option[A]

  def map[B](f: A => B): Response[B]

  def flatMap[B](f: A => Response[B]): Response[B]
}

case class Success[+A](value: A) extends Response[A] {

  override val returnValue: Option[A] = value match {
    case _: Unit => None
    case _       => Option(value)
  }

  override def map[B](f: (A) => B): Response[B] =
    try {
      Success(f(value))
    } catch {
      case NonFatal(e) => GenericFailure(s"Failed to map service response with value: $value", Some(e))
    }

  override def flatMap[B](f: A => Response[B]): Response[B] = {
    f(value)
  }
}

object Success {

  def empty: Success[Unit] = Success(())
}

trait NoValueResponse {
  self: Response[Nothing] =>

  override val returnValue: Option[Nothing] = None

  override def map[B](f: (Nothing) => B): Response[B] = this

  override def flatMap[B](f: (Nothing) => Response[B]): Response[B] = this
}

object NoChange extends Response[Nothing] with NoValueResponse

object Accepted extends Response[Nothing] with NoValueResponse

sealed trait Failure extends Response[Nothing] with NoValueResponse {

  def message: String
}

case class NoSuchElement(message: String) extends Failure

case class IllegalArgument(message: String, cause: Option[Throwable] = None) extends Failure

case class GenericFailure(message: String, cause: Option[Throwable] = None) extends Failure

ResponseScala2.scala

import scala.util.control.NonFatal

/**
 * A semi-monad representing the response of a service's operation, which may or may not contain a return value.
 *
 * @tparam A The type of the (optional) return value.
 */
sealed trait Response[+A] {

  /* --- Methods --- */

  /* --- Public Methods --- */

  /**
   * @return The optional return-value.
   */
  def returnValue: Option[A]

  /**
   * @param f The given function.
   * @tparam B The type of the given function's return value.
   * @return The result of applying the given function to this response's return value, or the response itself if it
   *         has no return value.
   */
  def map[B](f: A => B): Response[B]

  /**
   * @param f The given function.
   * @tparam B The type of the given function's response's return value.
   * @return The result of applying the given function to this response's return value, or the response itself if it
   *         has no return value.
   */
  def flatMap[B](f: A => Response[B]): Response[B]
}

/**
 * A response indicating that the operation has been successful.
 *
 * @tparam A The type of the (optional) return value.
 */
case class Success[+A](value: A) extends Response[A] {

  /* --- Methods --- */

  /* --- Public Methods --- */

  override val returnValue: Option[A] = value match {
    case _: Unit => None
    case _       => Option(value)
  }

  override def map[B](f: (A) => B): Response[B] =
    try {
      Success(f(value))
    } catch {
      case NonFatal(e) => GenericFailure(s"Failed to map service response with value: $value", Some(e))
    }

  override def flatMap[B](f: A => Response[B]): Response[B] = {
    f(value)
  }

}

object Success {

  /* --- Constructors --- */

  def empty: Success[Unit] = Success(())
}

/**
 * A response with no return value.
 */
trait NoValueResponse {
  self: Response[Nothing] =>

  /* --- Methods --- */

  /* --- Public Methods --- */

  override val returnValue: Option[Nothing] = None

  override def map[B](f: (Nothing) => B): Response[B] = this

  override def flatMap[B](f: (Nothing) => Response[B]): Response[B] = this
}

/**
 * A response indicating that the operation -- although it did not fail -- has made no changes to the service's
 * resources.
 */
object NoChange extends Response[Nothing] with NoValueResponse

/**
 * A response indicating that the operation has been successfully accepted by the service.
 */
object Accepted extends Response[Nothing] with NoValueResponse

/**
 * A response indicating that the operation has failed.
 */
sealed trait Failure extends Response[Nothing] with NoValueResponse {

  /* --- Methods --- */

  /* --- Public Methods --- */

  /**
   * @return A message which details the reason for the failure.
   */
  def message: String
}

/**
 * A response of an operation which have failed to locate one of the requested element.
 *
 * @param message A detailed message of the failure.
 * @see [[NoSuchElementException]]
 */
case class NoSuchElement(message: String) extends Failure

/**
 * A response of an operation which have received an illegal or inappropriate argument.
 *
 * @param message A detailed message of the failure.
 * @param cause   An optional throwable with further details of the failure.
 * @see [[IllegalArgumentException]]
 */
case class IllegalArgument(message: String, cause: Option[Throwable] = None) extends Failure

/**
 * A response of a generic (non-specific) failure of an operation.
 *
 * @param message A detailed message of the failure.
 * @param cause   An optional throwable with further details of the failure.
 */
case class GenericFailure(message: String, cause: Option[Throwable] = None) extends Failure

ResponseScala3-extensions.scala

sealed trait Response[+A] {
  case Success(value: A)
  case sealed trait NoValueResponse {
    case NoChange
    case Accepted
    case sealed trait Failure {
      case NoSuchElement(message: String)
      case IllegalArgument(message: String, cause: Option[Throwable] = None)
      case GenericFailure(message: String, cause: Option[Throwable] = None)
    }
  }
}

object Response {

  implicit class Ops[A](response: Response[A]) {

    def returnValue: Option[A] = response match {
      case Success(value) => value match {
        case _: Unit => None
        case _       => Option(value)
      }
      case _: NoValueResponse => None
    }

    def map[B](f: A => B): Response[B] = response match  {
      case Success(value) =>
        try {
          Success(f(value))
        } catch {
          case NonFatal(e) => GenericFailure(s"Failed to map service response with value: $value", Some(e))
        }
      case noValue: NoValueResponse => noValue
    }

    def flatMap[B](f: A => Response[B]): Response[B] = response match {
      case Success(value) =>f(value)
      case noValue: NoValueResponse => noValue
    }
  }
}

object Success {
  def empty: Success[Unit] = Success(())
}

object Failure 
  implicit class Ops(failure: Failure) {
    def message: String = failure match {
      case NoSuchElement(message) => message
      case IllegalArgument(message, _) => message
      case GenericFailure(message, _) => message
    }
  }
}

ResponseScala3.scala

sealed trait Response[+A] {
  def returnValue: Option[A]
  def map[B](f: A => B): Response[B]
  def flatMap[B](f: A => Response[B]): Response[B]
  
  case Success(value: A) {
    override val returnValue: Option[A] = value match {
      case _: Unit => None
      case _       => Option(value)
    }
    
    override def map[B](f: (A) => B): Response[B] =
      try {
        Success(f(value))
      } catch {
        case NonFatal(e) => GenericFailure(s"Failed to map service response with value: $value", Some(e))
      }
    
    override def flatMap[B](f: A => Response[B]): Response[B] = {
      f(value)
    }
  }
  
  case sealed trait NoValueResponse {
    override val returnValue: Option[Nothing] = None
    override def map[B](f: (Nothing) => B): Response[B] = this
    override def flatMap[B](f: (Nothing) => Response[B]): Response[B] = this
    
    case NoChange
    case Accepted
    case sealed trait Failure {
      def message: String
      
      case NoSuchElement(message: String)
      case IllegalArgument(message: String, cause: Option[Throwable] = None)
      case GenericFailure(message: String, cause: Option[Throwable] = None)
    }
  }
}

object Success {
  def empty: Success[Unit] = Success(())
}