Handle.allow approach is great but it lacks some convenience syntax that is avaliable in Cats. This PR proposes the following syntax:

• for Option:

  • liftTo:

    Details

    import scala.util.*
    import cats.mtl.*, syntax.option.*
    
    case class MyErr(err: String) extends Exception(err)
    
    val res1 =
      Handle.allow:
        Some(123).liftTo[Try]("OOPS")
      .rescue: err =>
        Failure(MyErr(err))
    
    assertEquals(res1, Success(123))
    
    val res2 =
      Handle.allow:
        None.liftTo[Try]("OOPS")
      .rescue: err =>
        Failure(MyErr(err))
    
    assertEquals(res2, Failure(MyErr("OOPS")))    

  • raiseTo:

    Details

    import scala.util.*
    import cats.mtl.*, syntax.option.*
    
    case class MyErr(err: String) extends Exception(err)
    
    val res1 =
      Handle.allow:
        Some("OOPS").raiseTo[Try]
      .rescue: err =>
        Failure(MyErr(err))
    
    assertEquals(res1, Failure(MyErr("OOPS")))
    
    val res2 =
      Handle.allow:
        (None: Option[String]).raiseTo[Try]
      .rescue: err =>
        Failure(MyErr(err))
    
    assertEquals(res2, Success(()))

• for Either:

  • liftTo:

    Details

    import scala.util.*
    import cats.mtl.*, syntax.either.*
    
    case class MyErr(err: String) extends Exception(err)
    
    val res1 =
      Handle.allow:
        Right[String, Int](123).liftTo[Try]
      .rescue: err =>
        Failure(MyErr(err))
    
    assertEquals(res1, Success(123))
    
    val res2 =
      Handle.allow:
        Left[String, Int]("OOPS").liftTo[Try]
      .rescue: err =>
        Failure(MyErr(err))
    
    assertEquals(res2, Failure("OOPS"))