How to create a graphql schema that can be searched on different fields?

Question

I'm testing out sangria to build a graphql/relay server. I have a very simple User class:

case class User(
  id: Int,
  username: String,
  gender: Gender.Value)

I want to allow queries by either ID or username. I have created a schema that allows this, but the fields have different names:

val Query = ObjectType(
  "Query", fields[UserRepo, Unit](
    Field("user", OptionType(User),
      arguments = ID :: Nil,
      resolve = ctx => ctx.ctx.getUser(ctx arg ID)),
    Field("userByUsername", OptionType(User),
      arguments = Username :: Nil,
      resolve = ctx => ctx.ctx.getUserByUsername(ctx arg Username))
  ))

Unfortunately, I need to query these with different fields names, user and userByUsername, e.g.:

curl -G localhost:8080/graphql     
  --data-urlencode 'query={userByUsername(username: "Leia Skywalker") {id, username, gender}}'

or

curl -G localhost:8080/graph    
  --data-urlencode "query={user(id: 1025) {id, username, gender}}"

How can I create a schema that allows a single field called user to be queried on either ID or username? E.g. both of the following should return the same user object:

curl -G localhost:8080/graphql     
  --data-urlencode 'query={user(username: "Leia Skywalker") {id, username, gender}}'

or

curl -G localhost:8080/graph    
  --data-urlencode "query={user(id: 1025) {id, username, gender}}"

Answer 1

I finally worked it out:

val ID = Argument("id", OptionInputType(IntType), description = "id of the user")
val Username = Argument("username", OptionInputType(StringType), description = "username of the user")

val Query = ObjectType(
  "Query", fields[UserRepo, Unit](
    Field("user", OptionType(User),
      arguments = List(ID, Username),
      resolve = ctx => ctx.ctx.getUser(ctx.argOpt(ID), ctx.argOpt(Username)))
  ))

And getUser looks like:

def getUser(id: Option[Int], username: Option[String]): Option[User] = {

  if (id.isEmpty && username.isEmpty) {
    None
  }
  else {
    id.flatMap(i => users.find(_.id == i))
      .orElse(username.flatMap(u => users.find(_.username == u)))
  }
}