Apollo server does not serialize virtual property from Mongoose in sub objects

Question

Here are my typescript objects (simplified):

@ObjectType()
export default class Game {
  @Field(() => ID)
  id?: string

  @arrayProp({items: Player})
  @Field(() => [Player])
  players: Player[] = []
}

@ObjectType()
export class Player {
  @Field(() => ID)
  id?: string
}

It generates this schema using type-graphql:

type Game {
  id: ID!
  players: [Player!]!
}
type Player {
  id: ID!
}

I use a resolver to query the user's games:

@Resolver(() => User)
export class UserGameResolver {
  @FieldResolver(() => [Game])
  async ongoingGames(@Ctx('userId') userId: string) {
    return GameModel.find({'players.userId': userId, setup: null})
  }
}

And it produces this error: "GraphQL error: Cannot return null for non-nullable field Player.id"

What I already know:

Game and Player "id" field is a "virtual" field created by Mongoose as an alias for "_id" which is the real property (I don't want to manipulate _id on the frontend, I want to serialize the alias).
If I don't query the games' players, it works. So Game.id is properly serialize by my apollo server resolver. So for this object, the virtual property is accessed and serialized properly.
The player id exists and the virtual property works on mongoose side: if I do console.log(mongooseResult[0].players[0].id), I can see my player id in the console.
Apollo server is suppose to use this default field resolver for player.id: https://github.com/graphql/graphql-js/blob/master/src/execution/execute.js#L1181-L1199 (documentation: https://www.apollographql.com/docs/apollo-server/data/resolvers/#default-resolvers). Based on the source code the virtual property should be serialized, as it is accessed this way: 'player['id']'.

If someone has an clue about what is happening here, it would be great!

hasezoey hasezoey · Accepted Answer · 2020-04-18T09:59:38

you should try to use _id

if you really want to use id (the virtual), then you need to either use .toJson or .toObject with the options { virtuals: true }

return GameModel.find({'players.userId': userId, setup: null}).toObject({ virtuals: true });

Apollo server does not serialize virtual property from Mongoose in sub objects

1 Answers