monocle.law.OptionalLaws.scala Maven / Gradle / Ivy

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package monocle.law

import monocle.Optional
import monocle.internal.{IsEq, Monoids}
import cats.Id
import cats.data.Const
import cats.kernel.Monoid

case class OptionalLaws[S, A](optional: Optional[S, A]) {
  import IsEq.syntax

  def getOptionReplace(s: S): IsEq[S] =
    optional.getOrModify(s).fold(identity, optional.replace(_)(s)) <==> s

  def replaceGetOption(s: S, a: A): IsEq[Option[A]] =
    optional.getOption(optional.replace(a)(s)) <==> optional.getOption(s).map(_ => a)

  def replaceIdempotent(s: S, a: A): IsEq[S] =
    optional.replace(a)(optional.replace(a)(s)) <==> optional.replace(a)(s)

  def modifyIdentity(s: S): IsEq[S] =
    optional.modify(identity)(s) <==> s

  def composeModify(s: S, f: A => A, g: A => A): IsEq[S] =
    optional.modify(g)(optional.modify(f)(s)) <==> optional.modify(g compose f)(s)

  def consistentReplaceModify(s: S, a: A): IsEq[S] =
    optional.replace(a)(s) <==> optional.modify(_ => a)(s)

  def consistentModifyModifyId(s: S, f: A => A): IsEq[S] =
    optional.modify(f)(s) <==> optional.modifyF[Id](f)(s)

  def consistentGetOptionModifyId(s: S): IsEq[Option[A]] = {
    implicit val optionMonoid: Monoid[Option[A]] = Monoids.firstOption
    optional.getOption(s) <==> optional.modifyF[Const[Option[A], *]](a => Const(Some(a)))(s).getConst
  }
}