apiextensions: don't run openapi controller if genericapiserver disables

staging/src/k8s.io/apiextensions-apiserver/pkg/apiserver/apiserver.go

@@ -212,7 +212,11 @@ func (c completedConfig) New(delegationTarget genericapiserver.DelegationTarget)
 		return nil
 	})
 	s.GenericAPIServer.AddPostStartHookOrDie("start-apiextensions-controllers", func(context genericapiserver.PostStartHookContext) error {
-		if utilfeature.DefaultFeatureGate.Enabled(apiextensionsfeatures.CustomResourcePublishOpenAPI) {
+		// OpenAPIVersionedService and StaticOpenAPISpec are populated in generic apiserver PrepareRun().
+		// Together they serve the /openapi/v2 endpoint on a generic apiserver. A generic apiserver may
+		// choose to not enable OpenAPI by having null openAPIConfig, and thus OpenAPIVersionedService
+		// and StaticOpenAPISpec are both null. In that case we don't run the CRD OpenAPI controller.
+		if utilfeature.DefaultFeatureGate.Enabled(apiextensionsfeatures.CustomResourcePublishOpenAPI) && s.GenericAPIServer.OpenAPIVersionedService != nil && s.GenericAPIServer.StaticOpenAPISpec != nil {
 			go openapiController.Run(s.GenericAPIServer.StaticOpenAPISpec, s.GenericAPIServer.OpenAPIVersionedService, context.StopCh)
 		}