Add function and lambda accessor syntax

[NikkyAI]

may be a partial duplicate of #63 but have this code anyhow.. maybe it helps even a little bit

this allows validations of java libraries without needing to write a val ThatClass.someValue = getSomeValue() extensions for each property

it also allows to use aliased custom accessors

a example out of our codebase using this to validate com.nimbusds.jwt.SignedJWT

fun ValidationBuilder<SignedJWT>.hasSubject(expectedSubject: String) {
    SignedJWT::getJWTClaimsSet required {
        JWTClaimsSet::getSubject required {
            addConstraint("subject must be '{0}'", expectedSubject) { subject ->
                subject == expectedSubject
            }
        }

    }
}

fun ValidationBuilder<SignedJWT>.hasClaimWithValue(claim: String, expected: String) {
    SignedJWT::getJWTClaimsSet required {
        val accessClaim = { it: JWTClaimsSet ->
            it.getStringClaim(claim) ?: null
        }
        accessClaim.required("getStringClaim($claim)") {
            addConstraint(
                "claim '{0}' must be '{1}'",
                claim,
                expected
            ) { value ->
                value == expected
            }
        }
    }
}

i added tests functionAccessorSyntax, lambdaAccessorSyntax, complexLambdaAccessors to demonstrate usage of this syntax

[dhoepelman]

Looks interesting, I have definitely encountered this. On my list to review for inclusion

[dhoepelman]

If we wait long enough this will likely be solved by Kotlin itself, synthetic java accessors are scheduled for kotlin 2.1:
https://youtrack.jetbrains.com/issue/KT-8575/Support-Java-synthetic-property-references. It's currently available behind a language version feature flag, although I don't know the right incantation for 1.9 or 2.0.

Still, allowing constraints to be specified for any function/lambda seems a good feature to have in general, if only because I find it annoying to not be able to easily specify constraints on nested things. Supporting KFunction in addition to KProperty also makes a lot of sense.

[dhoepelman]

WDYT about this as an API for lambdas

Suggested change

	getPassword("getPasswordLambda") {
	minLength(1)
	}
	get("password", { it.password }) {
	minLength(1)
	}

I think that should be possible with

/**
 * Transform the value into anything else and add a validation for it.
 * @param name The name that should be reported in validation errors
 * @param prop The function to get the value you want add a validation on
 * @see run
 */
abstract fun <R> get(name: String, prop: (T) -> R, init: ValidationBuilder<R>.() -> Unit)

[dhoepelman]

Fixes #14

[NikkyAI]

yep, I think this works for us

[elijah-pl]

This issue you may find interesting 🙂
Having options for Kotlin pre-2.1 would be great though!
https://youtrack.jetbrains.com/issue/KT-8575/Support-Java-synthetic-property-references

[dhoepelman]

@NikkyAI @jillesvangurp Thanks a lot for the contribution! I've massaged the API into something I think can provide a good basis, see the new README. Intend to release this soon-ish as 0.7.0. Let me know if you have any feedback.

[jillesvangurp]

Great!