ScalazCustomOps.scala

import scalaz.{Failure, Semigroup, Success, Validation}

object ScalazCustomOps {

  implicit class ScalazValidationOps[+E, +A](validation: Validation[E, A]) {

    /**
      * Check both validations, in case of success of both return only one success result (the latter).
      * Otherwise collect failures.
      *
      * @tparam EE The type of the `Failure`
      * @tparam AA The type of the `Success`
      */
    def findOneSuccess[EE >: E, AA >: A](that: => Validation[EE, AA])
                                        (implicit es: Semigroup[EE]): Validation[EE, AA] =
      validation match {
        case Failure(e) => that match {
          case Failure(e0) => Failure(es.append(e, e0))
          case _ => Failure(e)
        }

        case Success(_) => that match {
          case Failure(e0) => Failure(e0)
          case success => success
        }
      }
    
    //Same as above but much cleaner :)
    def appendFailures[EE >: E, AA >: A](that: => Validation[EE, AA])
                                        (implicit es: Semigroup[EE]): Validation[EE, AA] = {
      implicit val semigroupAA: Semigroup[AA] = Semigroup.lastSemigroup[AA]
      validation +++ that
    }
  }
}