Monadic comprehension for Result

[LVMVRQUXL]

🤔 The problem

Using explicit types with builders returning an encapsulated value is sometimes difficult.

For example, assuming that we want to create a Person having a firstName and a lastName properties of type NotBlankString, and an age property of type StrictlyPositiveInt, we would have to do the following:

data class Person(
    val firstName: NotBlankString,
    val lastName: NotBlankString,
    val age: StrictlyPositiveInt
)

fun main() {
    val somebody = Person(
        firstName = "John".toNotBlankString().getOrThrow(),
        lastName = "Doe".toNotBlankString().getOrThrow(),
        age = 42.toStrictlyPositiveInt().getOrThrow()
    )
    println(somebody) // Person(firstName=John, lastName=Doe, age=42)
}

As you can see, we need to unwrap the value of the result each time we want to create an explicit type (we are using the getOrThrow function in the example).

💡 The idea

Introducing a new resultOf function that will encapsulate the computations of the Result type within the given block function could solve this issue.

package kotools.types.result

inline fun <T> resultOf(block: ResultContext.() -> T): Result<T> = TODO()

interface ResultContext

The ResultContext interface could implement the existing builders for a better adoption.
But these builders should return the explicit type instead of an encapsulated one.

Here's an example for the toNotBlankString builder:

interface ResultContext {
    fun String.toNotBlankString(): NotBlankString
}

Using the new resultOf function in the first example looks like this:

data class Person(
    val firstName: NotBlankString,
    val lastName: NotBlankString,
    val age: StrictlyPositiveInt
)

fun main() {
    somebody = resultOf {
        Person(
            firstName = "John".toNotBlankString(),
            lastName = "Doe".toNotBlankString(),
            age = 42.toStrictlyPositiveInt()
        )
    }.getOrThrow()
    println(somebody) // Person(firstName=John, lastName=Doe, age=42)
}

🙏 Help needed

Please give this post a reaction if you are interested in this feature, or comment it below if you have any suggestion.
We would love to have your feedback!

[LVMVRQUXL]

The resultOf function will act like the runCatching function with the ResultContext receiver:

// Produces the same output
ResultContext.runCatching { "John".toNotBlankString() }
resultOf { "John".toNotBlankString() }

[LVMVRQUXL]

This feature is live in Kotools Types 4.1.0.