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add more doctest to EitherT #3054

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Sep 25, 2019
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add more doctest to EitherT #3054

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257 changes: 256 additions & 1 deletion core/src/main/scala/cats/data/EitherT.scala
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Original file line number Diff line number Diff line change
@@ -1,7 +1,6 @@
package cats
package data

import cats.Bifunctor
import cats.instances.either._
import cats.syntax.either._

Expand All @@ -13,33 +12,155 @@ import cats.syntax.either._
* and lifted in to a `EitherT[F, C, B]` via `EitherT.left`.
*/
final case class EitherT[F[_], A, B](value: F[Either[A, B]]) {

/** Transform this `EitherT[F, A, B]` into a `F[C]`.
*
* Example:
* {{{
* scala> import cats.implicits._
* scala> import cats.data.EitherT
*
* scala> val eitherT: EitherT[List, String, Int] = EitherT[List, String, Int](List(Left("456"), Right(123)))
* scala> eitherT.fold(string => string.toInt, int => int)
* res0: List[Int] = List(456, 123)
* }}}
*/
def fold[C](fa: A => C, fb: B => C)(implicit F: Functor[F]): F[C] = F.map(value)(_.fold(fa, fb))

/** Transform this `EitherT[F, A, B]` into a `F[C]`.
*
* Example:
* {{{
* scala> import cats.implicits._
* scala> import cats.data.EitherT
*
* scala> val eitherT: EitherT[List, String, Int] = EitherT[List, String, Int](List(Right(123),Left("abc")))
* scala> eitherT.foldF(string => string.split("").toList, _ => List("123"))
* res0: List[String] = List(123, a, b, c)
* }}}
*/
def foldF[C](fa: A => F[C], fb: B => F[C])(implicit F: FlatMap[F]): F[C] = F.flatMap(value)(_.fold(fa, fb))

/**
* Example:
* {{{
* scala> import cats.implicits._
* scala> import cats.data.EitherT
*
* scala> val eitherT: EitherT[List,String,Int] = EitherT[List, String,Int](List(Right(123),Left("abc")))
* scala> eitherT.isLeft
* res0: List[Boolean] = List(false, true)
* }}}
*/
def isLeft(implicit F: Functor[F]): F[Boolean] = F.map(value)(_.isLeft)

/**
* Example:
* {{{
* scala> import cats.implicits._
* scala> import cats.data.EitherT
*
* scala> val eitherT: EitherT[List,String,Int] = EitherT[List, String,Int](List(Right(123),Left("abc")))
* scala> eitherT.isRight
* res0: List[Boolean] = List(true, false)
* }}}
*/
def isRight(implicit F: Functor[F]): F[Boolean] = F.map(value)(_.isRight)

/**
* Example:
* {{{
* scala> import cats.implicits._
* scala> import cats.data.EitherT
*
* scala> val eitherT: EitherT[List,String,Int] = EitherT[List, String,Int](List(Right(123),Left("abc")))
* scala> eitherT.swap
* res0: EitherT[List,Int,String] = EitherT(List(Left(123), Right(abc)))
* }}}
*/
def swap(implicit F: Functor[F]): EitherT[F, B, A] = EitherT(F.map(value)(_.swap))

/**
* Example:
* {{{
* scala> import cats.implicits._
* scala> import cats.data.EitherT
*
* scala> val eitherT: EitherT[List,String,Int] = EitherT[List, String,Int](List(Right(123),Left("abc")))
* scala> eitherT.getOrElse(456)
* res0: List[Int] = List(123, 456)
* }}}
*/
def getOrElse[BB >: B](default: => BB)(implicit F: Functor[F]): F[BB] = F.map(value)(_.getOrElse(default))

/**
* Example:
* {{{
* scala> import cats.implicits._
* scala> import cats.data.EitherT
*
* scala> val eitherT: EitherT[List,String,Int] = EitherT[List, String,Int](List(Right(123),Left("abc")))
* scala> eitherT.getOrElseF(List(456))
* res0: List[Int] = List(123, 456)
* }}}
*/
def getOrElseF[BB >: B](default: => F[BB])(implicit F: Monad[F]): F[BB] =
F.flatMap(value) {
case Left(_) => default
case Right(b) => F.pure(b)
}

/**
* Example:
* {{{
* scala> import cats.implicits._
* scala> import cats.data.EitherT
*
* scala> val e1: EitherT[Option,String,Int] = EitherT[Option, String,Int](Some(Right(123)))
* scala> e1.orElse(EitherT[Option,Boolean,Int](Some(Right(456))))
* res0: EitherT[Option, Boolean, Int] = EitherT(Some(Right(123)))
*
* scala> val e2: EitherT[Option,String,Int] = EitherT[Option, String,Int](Some(Left("abc")))
* scala> e2.orElse(EitherT[Option,Boolean,Int](Some(Left(true))))
* res1: EitherT[Option, Boolean, Int] = EitherT(Some(Left(true)))
* }}}
*/
def orElse[C, BB >: B](default: => EitherT[F, C, BB])(implicit F: Monad[F]): EitherT[F, C, BB] =
EitherT(F.flatMap(value) {
case Left(_) => default.value
case r @ Right(_) => F.pure(r.leftCast)
})

/**
* Example:
* {{{
* scala> import cats.implicits._
* scala> import cats.data.EitherT
*
* scala> val eitherT: EitherT[List,String,Int] =
* | EitherT[List, String,Int](List(Right(123),Left("abc")))
* scala> val pf: PartialFunction[String, Int] = {case "abc" => 456}
* scala> eitherT.recover(pf)
* res0: EitherT[List, String, Int] = EitherT(List(Right(123), Right(456)))
* }}}
*/
def recover(pf: PartialFunction[A, B])(implicit F: Functor[F]): EitherT[F, A, B] =
EitherT(F.map(value)(_.recover(pf)))

/**
* Example:
* {{{
* scala> import cats.implicits._
* scala> import cats.data.EitherT
*
* scala> val eitherT: EitherT[List,String,Int] =
* | EitherT[List, String,Int](List(Right(123),Left("abc")))
* scala> val pf: PartialFunction[String, EitherT[List, String, Int]] =
* | {case "abc" => EitherT[List, String, Int](List(Right(456)))}
* scala> eitherT.recoverWith(pf)
* res0: EitherT[List, String, Int] = EitherT(List(Right(123), Right(456)))
* }}}
*/
def recoverWith(pf: PartialFunction[A, EitherT[F, A, B]])(implicit F: Monad[F]): EitherT[F, A, B] =
EitherT(F.flatMap(value) {
case Left(a) if pf.isDefinedAt(a) => pf(a).value
Expand All @@ -48,36 +169,170 @@ final case class EitherT[F[_], A, B](value: F[Either[A, B]]) {

/**
* Inverse of `MonadError#attemptT`
*
* Example:
* {{{
* scala> import cats.implicits._
* scala> import cats.data.EitherT
*
* scala> val e1: EitherT[Option, Unit, Int] = EitherT[Option, Unit, Int](Some(Right(123)))
* scala> e1.rethrowT
* res0: Option[Int] = Some(123)
*
* scala> val e2: EitherT[Option, Unit, Int] = EitherT[Option, Unit, Int](Some(Left(())))
* scala> e2.rethrowT
* res1: Option[Int] = None
* }}}
*/
def rethrowT(implicit F: MonadError[F, _ >: A]): F[B] =
F.rethrow(value)

/**
* Example:
* {{{
* scala> import cats.implicits._
* scala> import cats.data.EitherT
*
* scala> val eitherT: EitherT[List, String, Int] = EitherT[List, String, Int](List(Right(123), Left("abc")))
* scala> eitherT.valueOr(_.length)
* res0: List[Int] = List(123, 3)
* }}}
*/
def valueOr[BB >: B](f: A => BB)(implicit F: Functor[F]): F[BB] = fold(f, identity)

/**
* Example:
* {{{
* scala> import cats.implicits._
* scala> import cats.data.EitherT
*
* scala> val eitherT: EitherT[List, String, Int] = EitherT[List, String, Int](List(Right(123), Left("abc")))
* scala> eitherT.valueOrF(string => List(string.length))
* res0: List[Int] = List(123, 3)
* }}}
*/
def valueOrF[BB >: B](f: A => F[BB])(implicit F: Monad[F]): F[BB] =
F.flatMap(value) {
case Left(a) => f(a)
case Right(b) => F.pure(b)
}

/**
* Example:
* {{{
* scala> import cats.implicits._
* scala> import cats.data.EitherT
*
* scala> val eitherT: EitherT[List, String, Int] = EitherT[List, String, Int](List(Right(123), Left("abc")))
* scala> eitherT.forall(_ > 100)
* res0: List[Boolean] = List(true, true)
* }}}
*/
def forall(f: B => Boolean)(implicit F: Functor[F]): F[Boolean] = F.map(value)(_.forall(f))

/**
* Example:
* {{{
* scala> import cats.implicits._
* scala> import cats.data.EitherT
*
* scala> val eitherT: EitherT[List, String, Int] = EitherT[List, String, Int](List(Right(123), Left("abc")))
* scala> eitherT.exists(_ > 100)
* res0: List[Boolean] = List(true, false)
* }}}
*/
def exists(f: B => Boolean)(implicit F: Functor[F]): F[Boolean] = F.map(value)(_.exists(f))

/**
* Example:
* {{{
* scala> import cats.implicits._
* scala> import cats.data.EitherT
*
* scala> val e1: EitherT[List, String, Int] = EitherT[List, String, Int](List(Right(123), Left("abc")))
* scala> e1.ensure("error")(_ > 150)
* res0: EitherT[List, String, Int] = EitherT(List(Left(error), Left(abc)))
*
* scala> val e2: EitherT[List, String, Int] = EitherT[List, String, Int](List(Right(123), Left("abc")))
* scala> e2.ensure("error")(_ > 100)
* res1: EitherT[List, String, Int] = EitherT(List(Right(123), Left(abc)))
* }}}
*/
def ensure[AA >: A](onFailure: => AA)(f: B => Boolean)(implicit F: Functor[F]): EitherT[F, AA, B] =
EitherT(F.map(value)(_.ensure(onFailure)(f)))

/**
* Example:
* {{{
* scala> import cats.implicits._
* scala> import cats.data.EitherT
*
* scala> val e1: EitherT[List, String, Int] = EitherT[List, String, Int](List(Right(123), Left("abc")))
* scala> e1.ensureOr(_ => "error")(_ > 100)
* res0: EitherT[List, String, Int] = EitherT(List(Right(123), Left(abc)))
*
* scala> val e2: EitherT[List, String, Int] = EitherT[List, String, Int](List(Right(123), Left("abc")))
* scala> e2.ensureOr(_ => "error")(_ > 150)
* res1: EitherT[List, String, Int] = EitherT(List(Left(error), Left(abc)))
* }}}
*/
def ensureOr[AA >: A](onFailure: B => AA)(f: B => Boolean)(implicit F: Functor[F]): EitherT[F, AA, B] =
EitherT(F.map(value)(_.ensureOr(onFailure)(f)))

/**
* Example:
* {{{
* scala> import cats.implicits._
* scala> import cats.data.EitherT
*
* scala> val eitherT: EitherT[List, String, Int] = EitherT[List, String, Int](List(Right(123), Left("abc")))
* scala> eitherT.toOption
* res0: OptionT[List, Int] = OptionT(List(Some(123), None))
* }}}
*/
def toOption(implicit F: Functor[F]): OptionT[F, B] = OptionT(F.map(value)(_.toOption))

/**
* Example:
* {{{
* scala> import cats.implicits._
* scala> import cats.data.EitherT
*
* scala> val eitherT: EitherT[List, String, Int] = EitherT[List, String, Int](List(Right(123), Left("abc")))
* scala> eitherT.to[Option]
* res0: List[Option[Int]] = List(Some(123), None)
* }}}
*/
def to[G[_]](implicit F: Functor[F], G: Alternative[G]): F[G[B]] =
F.map(value)(_.to[G])

/**
* Example:
* {{{
* scala> import cats.implicits._
* scala> import cats.data.EitherT
*
* scala> val eitherT: EitherT[List, String, Int] =
* | EitherT[List, String, Int](List(Right(123), Left("abc")))
* scala> eitherT.collectRight
* res0: List[Int] = List(123)
* }}}
*/
def collectRight(implicit FA: Alternative[F], FM: Monad[F]): F[B] =
FM.flatMap(value)(_.to[F])

/**
* Example:
* {{{
* scala> import cats.implicits._
* scala> import cats.data.EitherT
*
* scala> val eitherT: EitherT[List, String, Int] =
* | EitherT[List, String, Int](List(Right(123), Left("abc")))
* scala> eitherT.bimap(string => string.length, int => int % 100)
* res0: EitherT[List, Int, Int] = EitherT(List(Right(23), Left(3)))
* }}}
*/
def bimap[C, D](fa: A => C, fb: B => D)(implicit F: Functor[F]): EitherT[F, C, D] =
EitherT(F.map(value)(_.bimap(fa, fb)))

Expand Down