Support for generic supertypes

[brezinajn]

This works fine:

@GraphQLQueryRoot
class Query {
    fun foo(): Int {
        ...
    }
} {

This doesn't:

interface SomeGenericInterface<T>

@GraphQLQueryRoot
class Query: SomeGenericInterface<String>{
    fun foo(): Int {
        ...
    }
}{

There should be no practical difference for the code generator between those two.

[martinbonnin]

Hey @brezinajn 👋 Apologies for the delay! We're looking into this together with @oas004 and wondering what the desired outcome was. Do you want SomeGenericInterface to be part of your GraphQL schema?

By default, empty Kotlin interfaces generate GraphQL unions:

union SomeGenericInterface = Query

type Query {
  foo: Int!
}

But it sounds like this is not the desired behaviour here? Did you just want the supertype ignored?

[brezinajn]

In my optinion the supertype should be ignored.

[martinbonnin]

Thanks for the reply! Ignoring makes sense. The issue is that by default GraphQL has interfaces and so the processor maps Kotlin interfaces to GraphQL classes:

Kotlin:

sealed interface Node {
    id: String
}
class User(
    override val id: String
) : Node

GraphQL:

interface Node {
    id: String!
}
type User implements Node {
    id: String!
}

We could ignore all non-sealed interfaces but I'm a bit wary this could come as surprising for someone new to the project and expecting an interface to be generated.

What about introducting @GraphQLIgnore? graphql-kotlin has the same and it could be used for other things that interfaces:

@GraphQLIgnore
interface SomeGenericInterface<T>

@GraphQLQuery
class Query: SomeGenericInterface<String>{
    fun foo(): Int = TODO()
 
    @GraphQLIgnore
    fun internalFields(): Int = TODO()
}{

type Query {
    foo: Int!
}

Thoughts?