Wsrtjtyk

I'm getting this error when trying to query a type and a descendant:

"Fragment cannot be spread here as objects of type "AppTestObject" can never be of type "AppTestChild"."

I set up a test install using recipe-core, admin, graphql, and graphql-devtools (all latest) to test this out in a basic setting. I've created 2 objects:

class TestObject extends DataObject {



    private static $singular_name = "Test Object";

    private static $plural_name = "Test Objects";

    private static $table_name = "TestObject";



    private static $db = [

        'Title' => 'Varchar(255)'

    ];



}



class TestChild extends DataObject {



    private static $singular_name = "Test Child";

    private static $plural_name = "Test Children";

    private static $table_name = "TestChild";



    private static $db = [

        'Title' => 'Varchar(255)'

    ];



}

And set up simple scaffolding through configuration:

SilverStripeGraphQLController:

  schema:

    scaffolding:

      types:



        AppTestObject:

          fields: [ID]

          operations:

            read: true



        AppTestChild:

          fields: [ID, Title]

          operations:

            read: true

I'm able to query each of these types individually without any problems. But when I try to get TestChild as a descendant of TestObject I get the error above. Here's an example of my query:

query {

  readAppTestObjects {

    edges {

      node {

        ...on AppTestChild {

          Title

        }

      }

    }

  }

}

Checking the documentation for the schema in graphiql, there is nothing under readAppTestObjects referencing descendants, although in the documentation for silverstripe/graphql it says:

When reading types that have exposed descendants (e.g. reading Page, when RedirectorPage is also exposed), the return type is a union of the base type and all exposed descendants. This union type takes on the name {BaseType}WithDescendants.

Yeah this is a bug in the SilverStripe graphql module. What you're doing should work.

I believe the fix is in flight at https://github.com/silverstripe/silverstripe-graphql/pull/176, you can follow the progress there. Maybe try the patch out and leave some comments.