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Added orElse combinator to IO #2940

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merged 5 commits into from
Apr 6, 2022
Merged

Added orElse combinator to IO #2940

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4a931cf
Added orElse combinator to IO
Apr 4, 2022
0c7218c
Merge branch 'typelevel:series/3.x' into series/3.x
walesho Apr 4, 2022
ebe93f2
Added orElse combinator to IO
Apr 5, 2022
406841c
Added orElse combinator on IO
Apr 5, 2022
ce8e089
Added orElse combinator to IO
Apr 5, 2022
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9 changes: 9 additions & 0 deletions core/shared/src/main/scala/cats/effect/IO.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -451,6 +451,15 @@ sealed abstract class IO[+A] private () extends IOPlatform[A] {
def handleError[B >: A](f: Throwable => B): IO[B] =
handleErrorWith[B](t => IO.pure(f(t)))

/**
* Runs the current IO, if it fails with an error(exception), the other IO will be executed.
* @param other
* IO to be executed (if the current IO fails)
* @return
*/
def orElse[B >: A](other: IO[B]): IO[B] =
SemigroupK[IO].combineK(this, other)
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I would go the other way around: leave this like you had it, and implement SemigroupK in terms of it.

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Thanks for the input. I would follow that approach.


/**
* Handle any error, potentially recovering from it, by mapping it to another `IO` value.
*
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10 changes: 10 additions & 0 deletions tests/shared/src/test/scala/cats/effect/IOSpec.scala
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Expand Up @@ -84,6 +84,16 @@ class IOSpec extends BaseSpec with Discipline with IOPlatformSpecification {
IO.raiseError[Unit](TestException).attempt must completeAs(Left(TestException))
}

"orElse must return other if previous IO Fails" in ticked { implicit ticker =>
case object TestException extends RuntimeException
(IO.raiseError[Int](TestException) orElse IO.pure(42)) must completeAs(42)
}

"Return current IO if successful" in ticked { implicit ticker =>
case object TestException extends RuntimeException
(IO.pure(42) orElse IO.raiseError[Int](TestException)) must completeAs(42)
}

"attempt is redeem with Left(_) for recover and Right(_) for map" in ticked {
implicit ticker =>
forAll { (io: IO[Int]) => io.attempt eqv io.redeem(Left(_), Right(_)) }
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