Graphql with Apollo Federation gives an Error on Entities: Non-shareable field is resolved from multiple subgraphs

[kunaliiti]

Describe the bug
I created two very simple subgraphs both using neo4j/graphql pointing to different neo4j instances. Both the subgraphs had just one entity "User" with different fields respectively. When combining these two subgraphs with Apollo Rover CLI. It gives out errors:

UNKNOWN: Non-shareable field "Query.users" is resolved from multiple subgraphs: it is resolved from subgraphs "gr1" and "gr2" and defined as non-shareable in all of them

Type definitions
Subgraph gr1 (app1.js):

import { ApolloServer } from "@apollo/server";
import { startStandaloneServer } from "@apollo/server/standalone";
import { Neo4jGraphQL } from "@neo4j/graphql";
import neo4j from "neo4j-driver";

const typeDefs = `#graphql
extend schema @link(url: "https://specs.apollo.dev/federation/v2.3", import: ["@key", "@shareable", "@external", "@override"])

type User @key(fields: "id") {
  id: ID!
  name: String!
}
`;

const driver = neo4j.driver("bolt://localhost:7687", neo4j.auth.basic("neo4j", "neo4j"));

const neo4jGraphQL = new Neo4jGraphQL({
    typeDefs,
    driver,
})

const schema = await neo4jGraphQL.getSubgraphSchema();

const server = new ApolloServer({
    schema,
});

const { url } = await startStandaloneServer(server, {
    context: async ({ req }) => ({ req, sessionConfig: { database: "fed1" } }),
    listen: { port: 5001 },
});
console.log(`🚀  Server ready at ${url}`);

Subgraph gr2 (app2.js):

import { ApolloServer } from "@apollo/server";
import { startStandaloneServer } from "@apollo/server/standalone";
import { Neo4jGraphQL } from "@neo4j/graphql";
import neo4j from "neo4j-driver";

const typeDefs = `#graphql
extend schema @link(url: "https://specs.apollo.dev/federation/v2.3", import: ["@key", "@shareable", "@external", "@provides"])

type User @key(fields: "id") {
  id: ID!
  age: Int!
}
`;

const driver = neo4j.driver("bolt://localhost:7687", neo4j.auth.basic("neo4j", "neo4j"));

const neo4jGraphQL = new Neo4jGraphQL({
  typeDefs,
  driver,
})

const schema = await neo4jGraphQL.getSubgraphSchema();

const server = new ApolloServer({
  schema,
});

const { url } = await startStandaloneServer(server, {
  context: async ({ req }) => ({ req, sessionConfig: { database: "fed2" } }),
  listen: { port: 5002 },
});
console.log(`🚀  Server ready at ${url}`);

Apollo Rover Configuration:

federation_version: =2.3.2
subgraphs:

  # Subgraph introspection
  gr1:
    routing_url: http://localhost:5001  # <- can be omitted if the same as introspection URL
    schema:
      subgraph_url: http://localhost:5001

  # Subgraph introspection
  gr2:
    routing_url: http://localhost:5002  # <- can be omitted if the same as introspection URL
    schema:
      subgraph_url: http://localhost:5002

To Reproduce
Steps to reproduce the behavior:

1. node app1.js
2. node app2.js
3. npx rover supergraph compose --config ./supergraph.yaml --output supergraph.graphql
4. See error

Expected behavior
Since the node "User" is defined as entity using the @key directive the below error should not be shown:

UNKNOWN: Non-shareable field "Query.users" is resolved from multiple subgraphs: it is resolved from subgraphs "gr1" and "gr2" and defined as non-shareable in all of them

System (please complete the following information):

• OS: macOS
• Version
  @apollo/server: 4.11.3,
  @neo4j/graphql: 5.12.0,
  graphql: 16.10.0,
  neo4j-driver: 5.28.1
  Rover: 0.28.1
• Node.js version: v20.15.1

Additional context
I also tried this with @neo4j/graphql: 6.6.0 and got the same error

[neo4j-team-graphql]

We've been able to confirm this bug using the steps to reproduce that you provided - many thanks @kunaliiti! 🙏 We will now prioritise the bug and address it appropriately.