Got Interfaces working in Sangria using the facebook spec examples

Example.scala

import sangria.schema._
import sangria.execution.Executor
import sangria.introspection.introspectionQuery
import sangria.integration.PlayJsonSupport._
import sangria.parser.{SyntaxError, QueryParser}
import sangria.renderer.SchemaRenderer
import scala.util.{Success,Failure}

trait NamedEntity{ val name: String }

case class Person(name: String, age: Int) extends NamedEntity
case class Business(name: String, employeeCount: Int) extends NamedEntity
case class Contact(entity: NamedEntity, phoneNumber: String, address: String)

object ContactRepo{
  val map = Map(
    "bob" -> Contact(Person("Bob Jones", 55), "555-1212", "1234 Rickshaw Drive"),
    "walmart" -> Contact(Business("Walmart", 200), "121-1555", "4321 Wahskcir Drive")
  )
  def get(name: String): Option[Contact] = map.get(name)
}

object GraphQL{
  val NamedEntityInterface: InterfaceType[Unit,NamedEntity] = InterfaceType[Unit,NamedEntity](
    name = "NamedEntity",
    fields = List[Field[Unit,NamedEntity]](Field("name", StringType, resolve = _.value.name))
  )

  val PersonObject = ObjectType[Unit,Person](
    name = "Person",
    fields = List[Field[Unit,Person]](Field("age", IntType, resolve = _.value.age)),
    interfaces = List(NamedEntityInterface)
  )

  val BusinessObject = ObjectType[Unit,Business](
    name = "Business",
    fields = List[Field[Unit,Business]](Field("employeeCount", IntType, resolve = _.value.employeeCount)),
    interfaces = List(NamedEntityInterface)
  )

  val ContactObject = ObjectType[Unit,Contact](
    name = "Contact",
    fields = List[Field[Unit,Contact]](
      Field("entity", NamedEntityInterface, resolve = _.value.entity),
      Field("phoneNumber", StringType, resolve = _.value.phoneNumber),
      Field("address", StringType, resolve = _.value.address)
    )
  )

  val NAME = Argument("name", StringType)

  val Query = ObjectType[ContactRepo.type,Unit](
    "Query",
      List[Field[ContactRepo.type, Unit]](
        Field("contact", OptionType(ContactObject), arguments = NAME :: Nil, resolve = (ctx) => ctx.ctx.get(ctx arg NAME)
      )
    )
  )

  val schema = Schema(
    query = Query,
    additionalTypes = List(NamedEntityInterface,PersonObject,BusinessObject)
  )

}

object Example extends App{
  import scala.concurrent.ExecutionContext.Implicits.global

  val executor = Executor(schema = GraphQL.schema, userContext = ContactRepo)
  val query = """
    {
      contact(name:"walmart"){
        entity{
          name
        }
      }
    }
  """
  val query2 = """
    {
      contact(name:"bob"){
        entity{
          name
          ... on Person {
            age
          }
        },
        phoneNumber
      }
    }
  """
  for{
    q <- List(query, query2)
  } {
    QueryParser.parse(q) match {
      case Success(queryAst) => executor.execute(queryAst).map(println)
      case Failure(error) => println(error)
    }
  }

  executor.execute(introspectionQuery) map (res =>
    SchemaRenderer.renderSchema(res) map println
  )

}