I’m working on a function where there is more than one possible failure path that I need to differentiate between. My paths are

1. success – return the value
2. logical error – non-fatal issue that the can be recovered from
3. exception – unexpected error that should be bubbled up

I found the arrow documentation here: https://arrow-kt.io/learn/typed-errors/working-with-typed-errors/ and read through it, but I’m still struggling to understand how to actually apply the information.

If I have some code like the following:

fun doValidation():Either<Error,String>
{
    val v1 = "123abc"
    val v2 = "abc"
    val v3 = "1234"
    validateName(v1)
    validateName(v2)
    validateName(v3)
}

fun validateName( value:String):Either<Error,String>
{
    if(value.length < 4)
    {
        //this is an unexpected exception
        return Error("$value has less than 4 characters").left()
    }
    else if(value.contains("abc"))
    {
        //this is a logical failure that we can recover from
        //this will not compile as-written
       return value.left()
    }
    else
    {
        return (value + "_xyz").right()
    }
}

what is the idiomatic way to implement validateName() such that doValidation can detect and recover from logical errors while still bubbling exceptions up the call stack?