Merge pull request #32586 from deads2k/api-05-restrict-versions

Automatic merge from submit-queue

restrict discoverable versions to those that have resources

Prevents versions with no resources from appearing in discovery.

@soltysh ptal.  I think you have some issues for this, mind wiring them up?

```
kubectl api-versions
apps/v1alpha1
authentication.k8s.io/v1beta1
authorization.k8s.io/v1beta1
autoscaling/v1
batch/v1
certificates.k8s.io/v1alpha1
extensions/v1beta1
policy/v1alpha1
rbac.authorization.k8s.io/v1alpha1
storage.k8s.io/v1beta1
v1
```
Fixes  #29998.

pkg/genericapiserver/genericapiserver.go

@@ -408,6 +408,10 @@ func (s *GenericAPIServer) InstallAPIGroup(apiGroupInfo *APIGroupInfo) error {
 		// Add a handler at /apis/<groupName> to enumerate all versions supported by this group.
 		apiVersionsForDiscovery := []unversioned.GroupVersionForDiscovery{}
 		for _, groupVersion := range apiGroupInfo.GroupMeta.GroupVersions {
+			// Check the config to make sure that we elide versions that don't have any resources
+			if len(apiGroupInfo.VersionedResourcesStorageMap[groupVersion.Version]) == 0 {
+				continue
+			}
 			apiVersionsForDiscovery = append(apiVersionsForDiscovery, unversioned.GroupVersionForDiscovery{
 				GroupVersion: groupVersion.String(),
 				Version:      groupVersion.Version,
@@ -422,6 +426,7 @@ func (s *GenericAPIServer) InstallAPIGroup(apiGroupInfo *APIGroupInfo) error {
 			Versions:         apiVersionsForDiscovery,
 			PreferredVersion: preferedVersionForDiscovery,
 		}
+
 		s.AddAPIGroupForDiscovery(apiGroup)
 		apiserver.AddGroupWebService(s.Serializer, s.HandlerContainer, apiPrefix+"/"+apiGroup.Name, apiGroup)
 	}

pkg/master/master_test.go

@@ -37,7 +37,7 @@ import (
 	apiv1 "k8s.io/kubernetes/pkg/api/v1"
 	"k8s.io/kubernetes/pkg/apimachinery/registered"
 	"k8s.io/kubernetes/pkg/apis/apps"
-	appsapi "k8s.io/kubernetes/pkg/apis/apps"
+	appsapiv1alpha1 "k8s.io/kubernetes/pkg/apis/apps/v1alpha1"
 	"k8s.io/kubernetes/pkg/apis/autoscaling"
 	autoscalingapiv1 "k8s.io/kubernetes/pkg/apis/autoscaling/v1"
 	"k8s.io/kubernetes/pkg/apis/batch"
@@ -137,7 +137,7 @@ func limitedAPIResourceConfigSource() *genericapiserver.ResourceConfig {
 		extensionsapiv1beta1.SchemeGroupVersion,
 		batchapiv1.SchemeGroupVersion,
 		batchapiv2alpha1.SchemeGroupVersion,
-		appsapi.SchemeGroupVersion,
+		appsapiv1alpha1.SchemeGroupVersion,
 		autoscalingapiv1.SchemeGroupVersion,
 	)
 	return ret