CustomVisitor.kt

override fun visitClassDeclaration(classDeclaration: KSClassDeclaration, data: Unit) {

    classDeclaration.annotations.firstOrNull { annotation ->
        // filter only JsonClass
        annotation.shortName.asString() == "JsonClass"
    }?.arguments?.firstOrNull { argument ->
        // check @JsonClass(generateAdapter = true)
        argument.name?.asString() == "generateAdapter" && argument.value == true
    }
        ?.let {
            // collect class to use in SymbolProcessor.finish()
            targets.add(classDeclaration)
        }

}