Aliasing a field to a @key field name yields Rust query planner error

[carldunham]

Describe the bug

Demonstrated in https://github.com/carldunham/apollo-router-6222.

Given the attached schema, this query

query Broken {
  animals {
    id: name
    name
    hello
  }
}

will succeed, but the logs show

2024-11-02T20:28:04.778921Z WARN  Rust query planner error in query `Broken`: An internal error has occurred, please report this bug to Apollo.

Details: Cannot merge field selection for field "Animal.name" into a field selection for field "Animal.id"

Similar queries will provide correct results and no issues logged:

query Works {
  animals {
    id
    name
    hello
  }
}

query WorksToo {
  animals {
    ident: id
    name
    hello
  }
}

To Reproduce

Steps to reproduce the behavior:

1. Clone the provided repo
2. Link, download, or copy whatever version of rover and router you want to test with
3. Run make supergraph run
4. Execute the provided query in the sandbox
5. See error in Router log
6. (if you want to see results, run the subgraph services like (cd a && make run)

Expected behavior

No issues logged.

Output

See above.

Desktop (please complete the following information):

• OS: MacOS
• Version 15.0.1

Additional context

Tested with various recent versions, up to

• Rover v0.26.2 with federation =2.9.0
• Router v1.57.0

[carldunham]

Note that setting

experimental_query_planner_mode: new

results in a query failure, naturally:

{
  "errors": [
    {
      "message": "value retrieval failed: Federation error: An internal error has occurred, please report this bug to Apollo.\n\nDetails: Cannot merge field selection for field \"Animal.name\" into a field selection for field \"Animal.id\"",
      "extensions": {
        "code": "INTERNAL_SERVER_ERROR"
      }
    }
  ]
}

[goto-bus-stop]

Thanks for the report. This is a known issue, I don't think we have a specific time frame in mind for addressing it (potentially after we remove the JS implementation of query planner from the router)

[carldunham]

potentially after we remove the JS implementation

But this would be a regression in Rust, no?

[goto-bus-stop]

I believe JS silently does the wrong thing in this case 🙈 (overwriting the aliased selection)

[carldunham]

Indeed it does!