Question: Splitting resolvers fails type check

[bglgwyng]

The following code passed type check. The definition of IResolvers is generated by mercurius-codegen.

const resolvers: IResolvers = {
  User: {
     // resolver code
  },
  Query,
  Mutation
}

I wanted to seperate the User resolver because it's quite large.

const User: UserResolvers = {
  // resolver code
}

const resolvers: IResolvers = {
  User,
  Query,
  Mutation
}

But then, the type check failed with this message.

Type '{ User: UserResolvers<MercuriusContext, User>; Query: QueryResolvers<MercuriusContext, {}>; Mutation: MutationResolvers<...>; }' is not assignable to type 'IResolvers<any, MercuriusContext>'.
  Property 'User' is incompatible with index signature.
    Type 'UserResolvers<MercuriusContext, User>' is not assignable to type 'GraphQLScalarType<unknown, unknown> | IEnumResolver | (() => any) | IResolverObject<any, MercuriusContext, any> | IResolverOptions<...> | undefined'.
      Type 'UserResolvers<MercuriusContext, User>' is not assignable to type 'IResolverObject<any, MercuriusContext, any>'.
        Property 'isTypeOf' is incompatible with index signature.
          Type 'IsTypeOfResolverFn<User, MercuriusContext>' is not assignable to type 'IResolverObject<any, MercuriusContext, any> | IResolverOptions<any, MercuriusContext, any> | IFieldResolver<...> | undefined'.
            Type 'IsTypeOfResolverFn<User, MercuriusContext>' is not assignable to type 'IFieldResolver<any, MercuriusContext, any>'.
              Types of parameters 'info' and 'context' are incompatible.
                Type 'MercuriusContext' is missing the following properties from type 'GraphQLResolveInfo': fieldName, fieldNodes, returnType, parentType, and 6 more.ts(2322)

When I switched UserResolvers to IResolvers["User"], the same message appeared.
How can I fix this problem?

[bglgwyng]

The error message above sounds like there is a mismatch of the position of context argument between IsTypeOfResolverFn and IFieldResolver.
So I added parent: {} to IsTypeOfResolverFn and the error got resolved.
Now my new IsTypeOfResolverFn definition reads as follows.

export type IsTypeOfResolverFn<T = {}, TContext = {}> = (
  parent: {}, // prepended
  obj: T,
  context: TContext,
  info: GraphQLResolveInfo
) => boolean | Promise<boolean>;

Is this the correct solution?

[EDjur]

Hi!

Bit of an old issue but I'm also running into this when splitting my resolvers like above.

@PabloSzx Do you have an idea if this is a bug or intended behaviour?

Thanks! 🙏