graphql-modules-preset is not adding interface and union resolvers to Module.Resolver

[ghost]

Describe the bug

When using graphql-module framework, the generated resolver is missing definition for interfaces and unions.
To Reproduce
Steps to reproduce the behavior:
Repo that reproduce the issue with readme for explanantion
https://github.com/laurent-lubino-roam/graphql-modules-codegen-resolver

Expected behavior

I would expect to be able to resolve types directly in the resolver using resolveType instead of isTypeOf

Environment:

• OS: macOS
• @graphql-codegen/graphql-module-preset:
• NodeJS: 16

Additional context

[the-ult]

Is there a way to fix/work around this?
Having the same problems with an union based on interfaces.

union MyUnion = InterfaceImpl1 | InterfaceImpl2 | InterfaceImpl3


interface MyInterface{
  id: String!
}

type InterfaceImpl1 implements MyInterface{
  id: String!
  ...
}

type InterfaceImpl2 implements MyInterface{
  id: String!
  ...
}

type InterfaceImpl3 implements MyInterface{
  id: String!
  ...
}

InterfaceImpl1, InterfaceImpl2 and InterfaceImpl3 are defined in the generated export interface Resolvers {}
But MyUnion is not

Same when only using Unions.
They are defined as types in the generated file but not in the resolver.

[ghost]

HI @the-ult, the workaround we've used was to define each type (InterfaceImpl1, InterfaceImpl2 and InterfaceImpl3) that implements the base interface (for you MyInterface) in the resolver and define a __isTypeOf like so:

export const resolvers: MyInterfaceModule.Resolvers = {
   InterfaceImpl3: {
       __isTypeOf: (obj) => {
           return obj.type === 'InterfaceImpl3' // or whatever helps you to identify your object type
      }
   }
}

instead of having one __resolveType in the base interface (MyInterface) resolver.

Also, we've stopped using union and the result types are using the base interface (eg. extend type Query { getMyInterface: MyInterface }), then in your queries, you can do something like:

query GetMyInterface {
    getMyInterface {
       id
       ... on InterfaceImpl1 { .... }
       ... on InterfaceImpl2 { .... }
       ... on InterfaceImpl3 { .... }
    }
}

Hope it helps.

[the-ult]

Thanks gonna try it out tomorrow.

Would be great though, if this could be fixed/added to the graphql-modules-preset

[the-ult]

@dotansimha is this issue a bug or a feature => intended?

---

I used to fix 🤔 it like this:

export const PersonResolvers: PersonModule.Resolvers | unknown = {}

But that way you'll lose all Typings.. 😳

Was trying it now like this:

export const PersonResolvers: PersonModule.Resolvers & { PersonUnion } = {}

Not much better, but at least this way we keep the types of all other PersonResolver properties.

Gonna try @laurent-lubino-roam way today.