Routing error when directly fetching properties on interfaces

[alexus37]

Component(s)

router

router version

v0.0.0-20240927172855-3e390cd5cf6c

What happened?

Description

The router is encountering an error when I try to retrieve the query plan for queries that directly fetch data from interfaces.

Steps to Reproduce

Execute a query like this:

{
  repository(name: "<REDACTED>", owner: "<REDACTED>") {
    issue(number: 1) {
      timelineItems(since: "<REDACTED>", first: 1) {
        edges {
          node {
            ... on Comment {
              id
              bodyText
            }
          }
        }
      }
    }
  }
}

where the Comment is an interface and not a type.

interface Comment {
  
  """
  The body rendered to text.
  """
  bodyText: String!

  """
  The Node ID of the Comment object
  """
  id: ID!
}

Expected Result

The correct query plan is being returned! This works perfectly when I directly fetch data from a type that implements that interface or when I simply retrieve the ID.

Actual Result

We are getting a execution plan failure.

Environment information

I am using the following headers:

{
  "X-WG-TRACE": "false",
  "X-WG-Skip-Loader": "true",
  "X-WG-Include-Query-Plan": "true",
}

Log output

AM ERROR internal error {"error": "1 error occurred:\n\t* could not resolve a field: internal: nodesResolvableVisitor: could not select the datasource to resolve Repository.__typename on path query.repository.__typename\n\n"}

[github-actions]

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[apatelWU]

I am facing similar issue as well where __typename required on interface object when fetching Id. If we are fetch other attributes of interface, then its working as expected.

For instance:
SubGraph A

interface A {
  a1Field: ID!
  a2Field: String
  a3Field: String
}

type XA implements A {
  a1Field: ID!
  a2Field: String
  a3Field: String
  xa1Field: String
}

type XB implements A {
  a1Field: ID!
  a2Field: String
  a3Field: String
  xb1Field: String
}

SubGraph B

type B {
  b1Field: ID!
  b2Field: String
  a: A!
}

query details:

query Test {
  b(id: ID!) {
    b1Field
    b2Field
    a {
      a1Field
    }
  }
}

The above query returns following error:
Subgraph 'B' returned invalid value 'A' for __typename field.

QueryPlan {
    SingleFetch(service: "B") {
        {
            b(id: $Id) {
                b1Field
                b2Field
                a {
                    __typename
                    a1Field
                }
            }
        }
    }
}

However, following queries returns data as expected

query Test {
  b(id: ID!) {
    b1Field: ID!
    b2Field: String
    a {
      a1Field
      a2Field
    }
  }
}

or

query Test {
  b(id: ID!) {
    b1Field: ID!
    b2Field: String
    a {
      __typename
      a1Field
    }
  }
}

[YassineElbouchaibi]

Noticed the same thing while creating repro for #1440.