Support for object union types about graphql

[jneurock]

I see. Thanks for pointing that out!! I looked for something like this when implementing the automatic union type resolution and I couldn't find it 😅 It was a question on my mind, whether or not a union type could be resolved for a single record.

This means that Mirage GraphQL makes the wrong assumption here and can't automatically resolve union types this way, for now. We'll have to put in a bug fix.

To get around this, you can supply your own resolver for the field. The resulting record will just need the __typename field populated and you should be able to keep going. I'm happy to help you with the resolver, if you'd like. You can join Mirage's Discord server: https://discord.gg/8PxR2E for more direct conversations. There's even a #graphql channel.

[jneurock]

Hey, thanks for the feedback!

At first glance, I think the issue is that the Basket type expects a singular fruit. I assume it would be more like a list of fruit, fruit: [Fruit], which should work with a union type.

[kdembler]

List of fruits would actually make more sense in a basket, maybe it was a bad choice of an example type on my part. 😅

The problem still stands - I'm looking to have a single value of union type, just like in the example.

Let's assume it's a very small basket :)

[jneurock]

No worries on the example. The same still applies; though, union types are intended for lists, as I understand it.

[kdembler]

Ah, I've missed that this was your point.

However, take a look at https://spec.graphql.org/June2018/#sec-Unions. The union definition doesn't have anything to do with a list and the example given in the spec doesn't use one.

[jneurock]

Here's an example resolver:

import { mirageGraphQLFieldResolver } from "@miragejs/graphql"

const graphQLHandler = createGraphQLHandler(schema, this.schema, {
  resolvers: {
    Basket: {
      fruit() {
        const [fruit] = mirageGraphQLFieldResolver(...arguments);

        return fruit;
      }
    }
  }
})

[jneurock]

Just to capture the necessary notes for fixing the bug:

• Mirage GraphQL almost has it right... it gets the right record but always returns a list.
• We need to check the return type of the field and make sure we don't just assume union type fields should resolve to a list.