Unexpected query planner error with fragments

[utay]

The query planner fails unexpectedly with the following error:
{
"message": "value retrieval failed: router bridge error: the deno runtime raised an error: request: couldn't receive response couldn't deserialize payload 5425825029548289619: deno: couldn't deserialize response : Error(\"invalid neither null nor empty object: found Object {\\\"code\\\": String(\\\"QUERY_PLANNING_FAILED\\\"), \\\"exception\\\": Object {\\\"stacktrace\\\": Array [String(\\\"Cannot add selection of field \\\\\\\"NBAPlayer.id\\\\\\\" to selection set of parent type \\\\\\\"PlayerInterface\\\\\\\"\\\")]}}\", line: 0, column: 0)``.",
"extensions": {
"code": "INTERNAL_SERVER_ERROR"
}
},

Minimal schema to reproduce

type Query {
  nbaCard: NBACard!
}

interface PlayerInterface {
  id: Int!
  slug: String!
}

interface CardInterface {
  id: Int!
  player: PlayerInterface!
}

type NBAPlayer implements PlayerInterface {
  id: Int!
  slug: String!
}

type NBACard implements CardInterface {
  id: Int!
  player: NBAPlayer!
}

Query to reproduce

{
    nbaCard {
      ...Fragment1
      ...Fragment2
    }
}

fragment Fragment1 on NBACard {
  player {
    id
  }
}

fragment Fragment2 on CardInterface {
  ...Fragment2_bis
}

fragment Fragment2_bis on CardInterface {
  player {
    slug
    __typename
  }
}

Notes:

• There's only one subgraph involved in the schema and query
• If I remove __typename from Fragment2_bis OR if I include Fragment2_bis directly in the query, it works
• I guess there's some sort of merging error because one player is of type NBAPlayer and the other of type PlayerInterface

Please let me know if I should report this issue on the JS repository (https://github.com/apollographql/federation) or feel free to do so!

[abernix]

Thanks for opening this! This might belong on the federation repository, but before I make the suggestion (or transfer it over there) — what version of the Router are you running? That'll determine the version of Federation at play.

[utay]

Thanks! I run the router version 1.18.0

[abernix]

Thanks. That would be Federation 2.4.2, then. I think this is fixed in Federation 2.4.3.

Let me demonstrate how I've validated this. First, at face-value, I'll point out the schema you shared is a non-federated schema. Running the Router or the Gateway requires a supergraph (which we also call a "core schema", sometimes). I definitely believe you know that, but it's worth pointing out since we need that supergraph to run query planning on (even if there is just one subgraph).

If I assume the schema you provided is offered as an example of a single subgraph that you're (somewhere outside of this issue) composing into a supergraph (for example, using rover supergraph compose), then it would yield a supergraph that looks like this:

schema
  @link(url: "https://specs.apollo.dev/link/v1.0")
  @link(url: "https://specs.apollo.dev/join/v0.3", for: EXECUTION)
{
  query: Query
}

directive @join__enumValue(graph: join__Graph!) repeatable on ENUM_VALUE

directive @join__field(graph: join__Graph, requires: join__FieldSet, provides: join__FieldSet, type: String, external: Boolean, override: String, usedOverridden: Boolean) repeatable on FIELD_DEFINITION | INPUT_FIELD_DEFINITION

directive @join__graph(name: String!, url: String!) on ENUM_VALUE

directive @join__implements(graph: join__Graph!, interface: String!) repeatable on OBJECT | INTERFACE

directive @join__type(graph: join__Graph!, key: join__FieldSet, extension: Boolean! = false, resolvable: Boolean! = true, isInterfaceObject: Boolean! = false) repeatable on OBJECT | INTERFACE | UNION | ENUM | INPUT_OBJECT | SCALAR

directive @join__unionMember(graph: join__Graph!, member: String!) repeatable on UNION

directive @link(url: String, as: String, for: link__Purpose, import: [link__Import]) repeatable on SCHEMA

interface CardInterface
  @join__type(graph: A)
{
  id: Int!
  player: PlayerInterface!
}

scalar join__FieldSet

enum join__Graph {
  A @join__graph(name: "a", url: "https://films.example.com")
}

scalar link__Import

enum link__Purpose {
  """
  `SECURITY` features provide metadata necessary to securely resolve fields.
  """
  SECURITY

  """
  `EXECUTION` features provide metadata necessary for operation execution.
  """
  EXECUTION
}

type NBACard implements CardInterface
  @join__implements(graph: A, interface: "CardInterface")
  @join__type(graph: A)
{
  id: Int!
  player: NBAPlayer!
}

type NBAPlayer implements PlayerInterface
  @join__implements(graph: A, interface: "PlayerInterface")
  @join__type(graph: A)
{
  id: Int!
  slug: String!
}

interface PlayerInterface
  @join__type(graph: A)
{
  id: Int!
  slug: String!
}

type Query
  @join__type(graph: A)
{
  nbaCard: NBACard!
}

If I run this with Federation 2.4.2's query planner, I reliably reproduce the error you gave. If I run it with Federation 2.4.3, then I get a valid query plan:

QueryPlan {
  Fetch(service: "a") {
    {
      nbaCard {
        player {
          __typename
          slug
          id
        }
      }
    }
  },
}

We updated the query planner to v2.4.5 just this morning (via some amends commits to the automated PR opened by Renovate apollographql/router#3107, so this should be fixed in the next release of the Router. We're working on the details of that releasing timing right now.

[utay]

This all makes sense, thank you for the details @abernix! Looking forward to the next release :)

[utay]

We upgraded the router to 1.19.0 which fixed the bug mentioned above. However, with the same schema, the query planner still fails with:
{
"message": "value retrieval failed: router bridge error: the deno runtime raised an error: request: couldn't receive response couldn't deserialize payload 12544047767499609238: deno: couldn't deserialize response : Error(\"invalid neither null nor empty object: found Object {\\\"code\\\": String(\\\"QUERY_PLANNING_FAILED\\\"), \\\"exception\\\": Object {\\\"stacktrace\\\": Array [String(\\\"Cannot add selection of field \\\\\\\"NBAPlayer.id\\\\\\\" to selection set of parent type \\\\\\\"PlayerInterface\\\\\\\"\\\")]}}\", line: 0, column: 0)``.",
"extensions": {
"code": "INTERNAL_SERVER_ERROR"
}
}

for this query:

{
  nbaCard {
    ...Fragment1
    ...Fragment2
    ...Fragment3
  }
}

fragment Fragment1 on NBACard {
  player {
    id
  }
}

fragment Fragment2 on CardInterface {
  player {
    slug
  }
}

fragment Fragment3 on CardInterface {
  player {
    __typename
  }
}

[abernix]

@utay Glad that fixed the first error. For the new bug, shouldn't you have a Fragment3 defined in that operation you provided? (If you agree, the error message makes this only quasi-clear and could be better.)

[utay]

Hmm but Fragment3 is defined, right? See the query above, it's not the same as the first one

[abernix]

Sorry, I forgot to scroll inside the codeblock. It is there and it is defined. 😉

[abernix]

@utay I transferred this over to the federation repository. Someone is going to take a look at it from that side. Any fix will surface in the Router via, presumably, a patch update.

Thanks again for logging this!

[utay]

Thank you @abernix and @pcmanus! Awesome to see that a PR is already opened :)