Possible Race condition in GraphQL schema generation

[TinyTrebuchet]

The graphql-spqr library assumes that interfaces can only be implemented by classes that resolve to GraphQLObjectType. If a Java Enum implements an interface and is discovered via its interface, it resolves to GraphQLEnumType and is stored in typeCache but is not added to discoveredTypes as it is not a GraphQLObjectType. This can result in a schema tree where no nodes actually contain the correct GraphQLEnum type mapping for the Java Enum, and are just resolved to GraphQLTypeReference

This creates a race condition: when an enum is resolved directly as a field/argument/return type, it is correctly represented, but if resolved via its interface, it fails to appear.

[TinyTrebuchet]

Currently fixed it in our project by skipping Enum implementations when mapping interfaces

class CustomImplementationDiscoveryStrategy extends DefaultImplementationDiscoveryStrategy
    @Override
    public List<AnnotatedType> findImplementations(AnnotatedType type, boolean autoDiscover, String[] scanPackages, BuildContext buildContext) {
        List<AnnotatedType> impls = super.findImplementations(type, autoDiscover, scanPackages, buildContext);
        return filterList(impls, impl -> !(impl.getType() instanceof Class && ((Class<?>) impl.getType()).isEnum()));
    }

This is working for now but need to know if this fix can have some other consequences, that we may not know of.

[kaqqao]

Thanks for reporting this. I'll have a look.
Any chance you make a reproducer/failing test?

[TinyTrebuchet]

No, couldn't reproduce this reliably in a test case.

[TinyTrebuchet]

Were you able to check this @kaqqao ?