Nested fields of @computed parent are not resolved

[marco-streng]

Issue workflow progress

Progress of the issue based on the Contributor Workflow

• [x] 1. The issue provides a reproduction available on Github, Stackblitz or CodeSandbox

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• [ ] 2. A failing test has been provided
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---

Describe the bug

Schema (User Service):

type User @canonical {
  id: ID!
  name: String!
  organizationId: String!
}

Schema (Organization Service):

type Organization {
  id: ID!
  name: String!
  users: [User!] 
}

type User @key(selectionSet: "{ id }") {
  id: ID!
  organization: Organization @computed(selectionSet: "{ organizationId }")
}

Query:

query DoesNotWork {
  users(ids: ["1", "2"]) { # user service
    name
    organization { # organization service with @computed directive
      name
      users { # user service
        name
      }
    }
  }
}

We have two services (User, Organization). Inside the Organization service we want to extend the type User with the field organization. Therefore we have to use the @computed directive. The type returned by the directive (in our case Organization) includes fields that must be resolved by the User service. This does not work and throws following error: Error: Cannot return null for non-nullable field User.name.

To Reproduce Steps to reproduce the behavior:

Open Sandbox and execute the default query named "DoesNotWork" in GraphiQL.

Expected behavior

Nested fields combined with the @computed directive are always resolved correctly.

Environment:

• @graphql-tools/schema": "^10.0.2"
• @graphql-tools/stitch": "^9.0.3"
• @graphql-tools/stitching-directives": "^3.0.0"
• NodeJS: v20