Consider aliases from discriminators during preparation

[danez]

I have the following use case:

const CarSchema = new Schema({ s: { type: Number, required: true, alias: "speed" } }, { discriminatorKey: 't' });
const Car = model('Car', CarSchema);

const TimeMachineSchema = new Schema({ f: { type: Number, required: true, alias: "fluxCompensatorVersion" } }, { discriminatorKey: 't' });
const TimeMachine = Car.discriminator('TimeMachine', TimeMachineSchema);

...

const CarDTC = composeWithMongooseDiscriminators(Car);

schemaComposer.Query.addFields({
  allCars: CarDTC.getResolver("findMany"),
});

...


gql`
{
  query FindAllCars() {
    allCars() {
      __typename
      speed

      ... on TimeMachine {
        fluxCompensatorVersion
      }
    }
  }
}
`

So we create a resolver from the base DTC which should be able to resolve all its discriminator documents.

The query does not work and errors with

Cannot return null for non-nullable field TimeMachine.fluxCompensatorVersion.

The reason is that in this example for Car the lib does not consider the aliases of all its discriminators, so it does not translate the alias for TimeMachine in this example.

Let me know what you think.

[nodkz]

I think it's great! 👍
Thanks a lot for this fix! 🙏

[github-actions]

🎉 This PR is included in version 8.0.3 🎉

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[github-actions]

🎉 This PR is included in version 9.0.0-alpha.8 🎉

The release is available on:

• npm package (@alpha dist-tag)
• GitHub release

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