Validation of uninitialized properties

[majster-kat]

Validation fails with UninitializedPropertyAccessException if I try to validate uninitialized lateinit variable.
For example:

class A {
    lateinit var v: String
}
validate(A()) {
    validate(A::v).isNotEmpty()
}

fails with exception kotlin.UninitializedPropertyAccessException: lateinit property v has not been initialized

I haven't found any solution in documentation for this situation (please correct me if I'm wrong). So here is my solution:

Create Uninitialized constraint and update validate method in Property to catch the exception.
Unitialized constraint is quite simple:

object Uninitialized : Constraint

Then new message should be added to messages.properties:

org.valiktor.constraints.Uninitialized.message=Must be initialized

And finally validate method can be updated like this:

fun validate(constraint: (T?) -> Constraint, isValid: (T?) -> Boolean): Property<T> {
    val value = try {
        this.property.get(this.obj)
    } catch(e: UninitializedPropertyAccessException) {
        this@Validator.constraintViolations += DefaultConstraintViolation(
                property = this.property.name,
                value = null,
                constraint = Uninitialized
        )
        return this
    }
    if (!isValid(value)) {
        this@Validator.constraintViolations += DefaultConstraintViolation(
            property = this.property.name,
            value = value,
            constraint = constraint(value)
        )
    }
    return this
}

Similarly coValidate should be updated as well.

[majster-kat]

If you like the idea, then I can create pull request.