What is the clean way to shortcut execution based on a boolean value in an `either` block? I current...

# arrow

[CLOVIS]

What is the clean way to shortcut execution based on a boolean value in an either block?
I currently have:

if (some condition) {
  val left: Either<Failure, DbUser> =
    UnknownFailure("some message here")
      .left()
  left.bind()
}

I would have just written

if (some condition)
    UnknownFailure("message").left().bind()

however, that casts the entire either block to Either<Failure, Nothing>.

[Cody Mikol]

Make the validation another function that returns an either

[CLOVIS]

It's just a validation though, there is no meaningful Right. Unless I make it have a Right(Unit), but that doesn't seem that clean

[Cody Mikol]

I often use a Unit for my right path on validation

[Cody Mikol]

There is actually a built in helper when you specifically want to do that with .void()

[Cody Mikol]

This is also a good use case for Either.conditionally(condition, {err}, {Unit}).bind()

[Cody Mikol]

fun validateCondition(foo: Foo) = Either.conditionally(foo.isValid, {UnknownFailure("bar")}, {Unit})

[kierans777]

@CLOVIS One step on the path to point free goodness is to not have imperative if statements. Passing functions to functions like Either.conditionally is the way to make the code cleaner.