Validator for value returned from a function

[Obirah]

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

The problem space this feature request arises from is the following:

In my Spring Boot Kotlin project, I'm using OpenAPI generator to generate API clients. I am generating Java client code, because I need the clients to use the Spring WebClient under the hood (because of a special authentication setup) and there is (to my knowledge) no way to generate Kotlin client code based on Spring WebClient.

Now, I need to validate the responses from those clients which are returned in classical PoJos with private members and public getters. Unfortunately, I can neither validate those PoJos with:

validate(response) {
    validate(ApiResponse::id).isNotBlank()
}

nor with:

validate(response) {
    validate(ApiResponse::getId).isNotBlank()
}

because both of those references point to KFunction and not a KProperty.

Describe the solution you'd like

The coolest way would be to have a validate function which takes a KFunction instead of a KProperty and validates the returned value in the same look and feel as the property validation.

Describe alternatives you've considered

Right now I'm using https://github.com/rcapraro/kalidation because it allows me to do something like that:

constraints<ApiResponse>{
    returnOf(ApiResponse::getId) {
        notBlank()
    }
}

Nonetheless, I think that the feature set of valiktor is way better. Therefore, using kalidation feels like a step backwards.