x-nullable for swagger-akka-http

SwaggerDocService.scala

class SwaggerDocService(canonicalHost: String, canonicalPort: Int)(
    implicit override val actorSystem: ActorSystem,
    override val materializer: ActorMaterializer
) extends SwaggerHttpService
    with HasActorSystem {

  override val apiTypes = Seq(
    // your routes
    typeOf[XNullableExtender] // you register listeners the same way as routes. The reader will sort out what is what
  )

XNullableExtender.scala

import io.swagger.jaxrs.config.ReaderListener
import io.swagger.models.Swagger
import scala.collection.JavaConverters._

class XNullableExtender extends ReaderListener {

  override def afterScan(reader: Reader, swagger: Swagger) = {

    val definitions: mutable.Map[String, Model] = swagger.getDefinitions.asScala

    definitions.foreach(kv => {
      val (_, model) = kv
      val properties: mutable.Map[String, Property] = model.getProperties.asScala
      properties.foreach(kv => {
        val (_, property) = kv
        if (!property.getRequired) {
          val extensions: mutable.Map[String, AnyRef] = property.getVendorExtensions.asScala
          extensions("x-nullable") = Predef.boolean2Boolean(true)
        }
      })
    })
  }

  override def beforeScan(reader: Reader, swagger: Swagger) = {}
}