Validate a collection of primitive values

[mattupstate]

Is your feature request related to a problem? Please describe.

Giving Valiktor a try and it's not clear to me how to validate a collection of primitive values. For example, is it not possible to validate each value in a Set<String> with isNotBlank()?

Describe the solution you'd like

Perhaps something like:

data class Request(val emailAddresses: List<String>? = null)

validate(Request(listOf("hello@world.com", "goodbye")) {
   validate(Request::emailAddresses)
    .isNotNull()
    .hasSize(min = 1)
    .eachIsNotBlank()
    .eachIsEmail()
}

Describe alternatives you've considered

Otherwise it seems I have to make the type for the collection a value or data class with one field:

value class StringValue(val value: String)

data class Request(val emailAddresses: List<StringValue>? = null)

validate(Request(listOf("hello@world.com", "goodbye")) {
   validate(Request::emailAddresses)
    .isNotNull()
    .hasSize(min = 1)
    .validateForEach {
      validate(StringValue::value)
        .isNotBlank()
        .isEmail()
    }
}

Additional context

While I don't personally mind value classes like this, it's not exactly leading to the API design I'd like for JSON/HTTP interfaces.

[makcon]

I've stuck with the same problem, would be good to have it. Thanks

[PierrickPuimeanChieze]

Solution could be to build your own DefaultConstraintsValidation. Something like that.

data class Request(val emailAddresses: List<String>? = null) {
    fun executeValidation() {
        validate(this) {
            validate(Request::emailAddresses).addConstraintViolations(
                it.emailAddresses
                    ?.mapIndexedNotNull { index, value ->
                        if (value.isEmail()) {
                            null
                        } else {
                            DefaultConstraintViolation(
                                property = "emailAddresses[$index]",
                                constraint = Email,
                                value = value
                            )
                        }
                    } ?: emptyList()
            )
        }
    }
}

fun String?.isEmail() = this == null || matches(
    Regex(
        "^[_A-Za-z0-9-\\+]+(\\.[_A-Za-z0-9-]+)*@[A-Za-z0-9-]+(\\.[A-Za-z0-9]+)*(\\.[A-Za-z]{2,})$"
    )
)

not the cleanest way to do it, I agree.