Federation Gateway resolving wrong field during buildQueryPlan

[WardGubbi]

I'm transforming my Apollo GraphQL into a federated one and I'm seeing an issue with property types in my inline fragments being resolved incorrectly and throwing an error on the gateway

The query in question

{
  grid(
    brand: "example.com"
    path: "C4054A88-1091-41B9-A53E-0AB2706DB2B8"
    pageNumber: 1
    displaySize: SMALL
  ) {
    cells {
      __typename
      ... on GridSlider {
        spanSize
      }

      ... on GridTeaser {
        spanSize
        config {
          type
          alignment
          ratio
          numbered
          stripped
        }
      }
      
      ... on GridHtml {
        spanSize
        config {
          url
          html
        }
      }

      ... on GridBanner {
        spanSize
        config {
          adUnit
          pageType
          slot
          format
        }
      }

      ... on GridHeader {
        spanSize
        config {
          title
          color
        }
      }
    }
  }
}

This results in an error on the gateway

"GraphQLError: Cannot query field \"type\" on type \"GridTeaserConfig\"",
"    at QueryPlanningContext.getFieldDef (/Users/Ward/Projecten/mediahuis/federation-repro/node_modules/@apollo/gateway/dist/buildQueryPlan.js:381:19)",
"    at collectFields (/Users/Ward/Projecten/mediahuis/federation-repro/node_modules/@apollo/gateway/dist/buildQueryPlan.js:256:42)",

The same request does work when fed to the service itself.

In my query it will try to resolve config.url from GridHtml as a property of GridTeaserConfig (note that the previous fragment was of type GridTeaser) instead of treating config as GridHtmlConfig. When removing the GridTeaser fragment (or removing its config) the issue repeats itself on the next config, config.adUnit being resolved as property of GridHtmlConfig instead of GridBannerConfig. Reordering (or deleting some fragments) shows that it always seems to resolve to the previous type's config instead of the correct one. Keeping only one of the configs (the HTML one for example) makes it work as expected.

I'm seeing this in @apollo/gateway 0.10.4

Here is a repository (adjusted demo repo) that reproduces the behavior: https://github.com/WardGubbi/graphql-federation

[thicit]

This issue seems to originate in the groups stage of the build query plan.
The field collection beforehand resolves correctly, however in the groups stage things go wrong.
completeFields & collectSubfields take the first field without considering parentType.

[geoffreysamper]

any news arround this issue

[geoffreysamper]

@thicit do you have any idea what must be done to fix this issue and get it merged?

[geoffreysamper]

This issue is fixed in #3581.

[abernix]

Fixed by #3581. Please report back if this isn't the case!