Interface objects are not put into the scan queue

[KammererTob]

I noticed a possible bug in the implementation of the scanner. If you add a complex property (object/enum) to an interface only it does not get detected, because interfaces are not added to the scanning queue.
Here is an example:

interface Competition {
    discipline: Discipline
}

type TestCompetition implements Competition {
    test: String
}

enum Discipline {
    TEST
}

extend type Query {
    competitions() : [Competition]
}

Discipline is not used anywhere else. On startup i get this warning:

c.c.graphql.tools.SchemaClassScanner : Schema type was defined but can never be accessed, and can be safely deleted: Discipline

And later this error:

Caused by: com.coxautodev.graphql.tools.SchemaError: Expected type 'Discipline' to be a GraphQLOutputType, but it wasn't! Was a type only permitted for object types incorrectly used as an input type, or vice-versa?

I tracked this bug(?) down to this method: https://github.com/graphql-java/graphql-java-tools/blob/master/src/main/kotlin/com/coxautodev/graphql/tools/SchemaClassScanner.kt#L263

It is neither an ObjectType nor an InputType and thus nothing happens with the interface. Am i doing something wrong or is this indeed a bug?

[KammererTob]

Error on my part. I forgot to implement the properties of the interface on the actual type and thus of course the enum wasn't scanned. Sorry for the inconvenience!

[lumberg72]

I'm brand new to this, but it seems your initial report is still valid.
If you put a complex object in an interface in the schema, and don't add it to any of the implemented types, it throws a misleading (at least from my perspective) error. I was only able to figure it out by finding this ticket.