getting "Cannot complete value of unexpected type X" error with children

[jaredh159]

I'm having trouble resolving the children of a model. I definitely might be doing something super dumb though. What's odd is, in my other vapor/graphql app (yes, I have two now...) I haven't hit this problem, but I use parent/children a decent bit. Anyway, I have models like this:

final class Order: Model, Content {
  static let schema = "orders"

  @ID(key: .id)
  var id: UUID?

  @Field(key: "email")
  var email: String

  @Children(for: \OrderItem.$order)
  var items: [OrderItem]

  init() {}
}

final class OrderItem: Model, Content {
  static let schema = "order_items"

  @ID(key: .id)
  var id: UUID?

  @Parent(key: "order_id")
  var order: Order

  @Field(key: "title")
  var title: String

  init() {}
}

The schema looks like this:

let AppSchema = try! Graphiti.Schema<Resolver, Request> {
  Scalar(UUID.self)

  Type(Order.self) {
    Field("id", at: \.id)
    Field("email", at: \.email)
    Field("items", with: \.$items)
  }

  Type(OrderItem.self) {
    Field("title", at: \.title)
    Field("order", with: \.$order)
  }

  Query {
    Field("getOrder", at: Resolver.getOrder) {
      Argument("id", at: \.id)
    }
  }
}

And the resolver looks like this:

final class Resolver {
  struct IdentifyEntityArgs: Codable {
    let id: UUID
  }

  func getOrder(
    request: Request,
    args: IdentifyEntityArgs
  ) throws -> Future<Order> {
    return Order.query(on: request.db)
      .with(\.$items)
      .filter(\.$id == args.id)
      .first()
      .unwrap(or: Abort(.notFound))
  }
}

But when I send a graphql query like so:

query {
  order: getOrder(id: "FBF9C172-E57E-49A8-8806-85F6C923E55A") {
    id
    items {
      title # <-- trying to get one of the children causes the error, without this, it works
    }
  }
}

I get the error Cannot complete value of unexpected type \"OrderItem\".

I feel like I'm missing something stupid. I think I'm sort of following your examples for users/todos in the readme.

If the code above isn't clear enough, I've created a super minimal reproduction repository using an in-memory sql-lite db. If you want to take a look, you can just clone the repo, then run swift run and (in another terminal tab) try bash ./test-error.sh to send the query shown above.

[jaredh159]

I accidentally created the issue before I described the problem, fixed now. Sorry about that.

[alexsteinerde]

I haven't had this issue before. Bug I could reproduce it (The example repo was very handy!) and I fixed it.
This GraphQL Swift api is a bit confusing.
By using the Order type in the query this type is registered automatically (implicitly).
The type OrderItem is not implicitly registered.
You can explicitly register the type OrderItem by adding this line to the bottom of your schema: Types(OrderItem.self) (Example: https://github.com/GraphQLSwift/Graphiti/blob/af903a243862c6427935677b91f67df0c21f2a71/Tests/GraphitiTests/StarWarsAPI/StarWarsAPI.swift#L101).
I hope this can help you.

[jaredh159]

Thanks! I’m away from my office for a few days, but I’ll check it out when I get back on Monday.

…

On Aug 26, 2021, at 6:41 AM, Alexander Steiner ***@***.***> wrote:  I haven't had this issue before. Bug I could reproduce it (The example repo was very handy!) and I fixed it. This GraphQL Swift api is a bit confusing. By using the Order type in the query this type is registered automatically (implicitly). The type OrderItem is not implicitly registered. You can explicitly register the type OrderItem by adding this line to the bottom of your schema: Types(OrderItem.self) (Example: https://github.com/GraphQLSwift/Graphiti/blob/af903a243862c6427935677b91f67df0c21f2a71/Tests/GraphitiTests/StarWarsAPI/StarWarsAPI.swift#L101). I hope this can help you. — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub, or unsubscribe. Triage notifications on the go with GitHub Mobile for iOS or Android.

[jaredh159]

Sure enough, that completely fixes it. Although I can't say that I understand fully why. It seems like there's a very explicit registration of the OrderItem type in the schema, when I define it as a GraphQL type using Type(OrderItem.self) { ... on this line. But I'm probably still missing a something.

Really appreciate the help, as always.

[alexsteinerde]

I agree, this doesn't seem perfect from an API perspective. But I also don't know enough about the Graphiti implementation so I can't explain the reason for this.
Maybe there will be a better way in the future.