Optional of List does not generate proper schema ref

[matlach]

Hi there,

In our application we rely on Optional<...> for each of our models properties to allow us to distinguish between "undefined" vs. "null" vs. "an actual value". When generating OpenAPI all schemas are properly referenced except for array-like data structure.

For example, using WildFly 23.0.2.Final which bundle SmallRye OpenAPI 2.1.2:

@Path("/aresources")
public class AResource {
    public static class A {
        public UUID id;
        public Optional<B> optionalOfB;
        public List<B> listOfB;
        public Optional<List<B>> optionalListOfB;
    }

    public static class B {
        public UUID id;
    }

    @GET @Path("/") @Operation(summary = "List A")
    public List<A> listA() {
        return Collections.emptyList();
    }
}

will generate the following yaml (excerpt):

openapi: 3.0.3
components:
  schemas:
    A:
      type: object
      properties:
        id:
          $ref: '#/components/schemas/UUID'
        listOfB:
          type: array
          items:
            $ref: '#/components/schemas/B'
        optionalListOfB:
          type: object
          nullable: true
        optionalOfB:
          allOf:
          - $ref: '#/components/schemas/B'
          - nullable: true
    B:
      type: object
      properties:
        id:
          $ref: '#/components/schemas/UUID'

but should have instead:

openapi: 3.0.3
components:
  schemas:
    A:
      type: object
      properties:
        id:
          $ref: '#/components/schemas/UUID'
        listOfB:
          type: array
          items:
            $ref: '#/components/schemas/B'
        optionalListOfB:
          type: array
          items:
            $ref: '#/components/schemas/B'
          nullable: true
        optionalOfB:
          allOf:
          - $ref: '#/components/schemas/B'
          - nullable: true
    B:
      type: object
      properties:
        id:
          $ref: '#/components/schemas/UUID'

I've also tested out the latest SmallRye OpenAPI 2.1.4, which had lead to the exact same result.

My guess is #210 does not cover this specific use case and/or there's an issue within the io.smallrye.openapi.runtime.util.TypeUtil.

Let me know if I can be any help to resolve this issue; this is last one preventing us migrating from Swagger to OpenAPI.

Thank you!