ExternalService implementation not working with ingress-rules

[BasLijten]

Describe the bug

I have created an external service to route my traffic. However, when trying to applying the ingress-rule, Yarp throws an error

To Reproduce

1. Create an external service and ingress rule for that service - By lack of documentation, I copied this from one of your test-assets. I had to add "ingressClassName: yarp", otherwise, Yarp would not even see changes in the ingress rules

apiVersion: v1
kind: Service
metadata:
  name: external-service
  namespace: default
spec:
  type: ExternalName
  externalName: external-service.example.com
--- 
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: external-ingress
  namespace: default
  annotations:
    yarp.ingress.kubernetes.io/backend-protocol: https
spec:
  ingressClassName: yarp
  rules:
  - http:
      paths:
      - pathType: Prefix
        path: /cb
        backend:
          service:
            name: external-service
            port:
              number: 443

2. Apply it kubectl apply -f .\ingress-external.yaml
3. what the exception being thrown

[06:48:46 DBG] Informer V1Service received Modified notification for Service/external-service.default at resource version 191835
[06:48:46 WRN] Uncaught exception occured while reconciling ingress default/external-ingress
System.ArgumentNullException: Value cannot be null. (Parameter 'source')
   at System.Linq.ThrowHelper.ThrowArgumentNullException(ExceptionArgument argument)
   at System.Linq.Enumerable.TryGetSingle[TSource](IEnumerable`1 source, Func`2 predicate, Boolean& found)
   at Yarp.Kubernetes.Controller.Converters.YarpParser.HandleIngressRule(YarpIngressContext ingressContext, List`1 endpoints, IList`1 defaultSubsets, V1IngressRule rule, YarpConfigContext configContext) in /src/src/Kubernetes.Controller/Converters/YarpParser.cs:line 42
   at Yarp.Kubernetes.Controller.Converters.YarpParser.ConvertFromKubernetesIngress(YarpIngressContext ingressContext, YarpConfigContext configContext) in /src/src/Kubernetes.Controller/Converters/YarpParser.cs:line 31
   at Yarp.Kubernetes.Controller.Services.Reconciler.ProcessAsync(CancellationToken cancellationToken) in /src/src/Kubernetes.Controller/Services/Reconciler.cs:line 56
[06:48:46 INF] [{"RouteId":"minimal-ingress.default:/foo","Match":{"Methods":null,"Hosts":[],"Path":"/foo/{**catch-all}","QueryParameters":null,"Headers":null},"Order":null,"ClusterId":"foo-service.default:8080","AuthorizationPolicy":null,"CorsPolicy":null,"MaxRequestBodySize":null,"Metadata":null,"Transforms":[{"PathPattern":"/{**catch-all}"}]},{"RouteId":"minimal-ingress.default:/bar","Match":{"Methods":null,"Hosts":[],"Path":"/bar/{**catch-all}","QueryParameters":null,"Headers":null},"Order":null,"ClusterId":"bar-service.default:8080","AuthorizationPolicy":null,"CorsPolicy":null,"MaxRequestBodySize":null,"Metadata":null,"Transforms":[{"PathPattern":"/{**catch-all}"}]}]
[06:48:46 INF] [{"ClusterId":"foo-service.default:8080","LoadBalancingPolicy":null,"SessionAffinity":null,"HealthCheck":null,"HttpClient":null,"HttpRequest":null,"Destinations":{"http://10.244.1.2:8080":{"Address":"http://10.244.1.2:8080","Health":null,"Metadata":null}},"Metadata":null},{"ClusterId":"bar-service.default:8080","LoadBalancingPolicy":null,"SessionAffinity":null,"HealthCheck":null,"HttpClient":null,"HttpRequest":null,"Destinations":{"http://10.244.1.3:8080":{"Address":"http://10.244.1.3:8080","Health":null,"Metadata":null}},"Metadata":null}]

Further technical details

• I was using the latest version in the main branch, as /release/latest didn't work with the kubernetes controller
• another ingress rule does exist. It doesn't matter if I include the external service with this definition

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: minimal-ingress
  annotations: 
    yarp.ingress.kubernetes.io/transforms: |
      - PathPattern: "/{**catch-all}"
spec:
  ingressClassName: yarp
  rules:
  - http:
      paths:      
      - pathType: Prefix
        path: /foo
        backend:
          service:
            name: foo-service
            port:
              number: 8080
      - pathType: Prefix
        path: /bar
        backend:
          service:
            name: bar-service
            port:
              number: 8080

• The platform (Linux/macOS/Windows): running Kubernetes in Docker on Windows 11. "Normal" services do work (find the blogpost here that I wrote)