Remove Generators from Factory

pkg/kubectl/cmd/expose.go

@@ -188,7 +188,7 @@ func (o *ExposeServiceOptions) Complete(f cmdutil.Factory, cmd *cobra.Command) e
 		return err
 	}
 
-	o.Generators = f.Generators
+	o.Generators = cmdutil.GeneratorFn
 	o.Builder = f.NewBuilder()
 	o.CanBeExposed = polymorphichelpers.CanBeExposedFn
 	o.ClientForMapping = f.ClientForMapping

pkg/kubectl/cmd/run.go

@@ -321,7 +321,7 @@ func (o *RunOptions) Run(f cmdutil.Factory, cmd *cobra.Command, args []string) e
 		}
 	}
 
-	generators := f.Generators("run")
+	generators := cmdutil.GeneratorFn("run")
 	generator, found := generators[generatorName]
 	if !found {
 		return cmdutil.UsageErrorf(cmd, "generator %q not found", generatorName)
@@ -573,7 +573,7 @@ func verifyImagePullPolicy(cmd *cobra.Command) error {
 }
 
 func (o *RunOptions) generateService(f cmdutil.Factory, cmd *cobra.Command, serviceGenerator string, paramsIn map[string]interface{}, namespace string) (*RunObject, error) {
-	generators := f.Generators("expose")
+	generators := cmdutil.GeneratorFn("expose")
 	generator, found := generators[serviceGenerator]
 	if !found {
 		return nil, fmt.Errorf("missing service generator: %s", serviceGenerator)

pkg/kubectl/cmd/util/BUILD

@@ -6,6 +6,7 @@ go_library(
         "conversion.go",
         "factory.go",
         "factory_client_access.go",
+        "generator.go",
         "helpers.go",
         "kubectl_match_version.go",
         "printing.go",

pkg/kubectl/cmd/util/factory.go

@@ -28,7 +28,6 @@ import (
 	scaleclient "k8s.io/client-go/scale"
 	api "k8s.io/kubernetes/pkg/apis/core"
 	"k8s.io/kubernetes/pkg/client/clientset_generated/internalclientset"
-	"k8s.io/kubernetes/pkg/kubectl"
 	"k8s.io/kubernetes/pkg/kubectl/cmd/util/openapi"
 	"k8s.io/kubernetes/pkg/kubectl/genericclioptions"
 	"k8s.io/kubernetes/pkg/kubectl/genericclioptions/resource"
@@ -68,8 +67,6 @@ type Factory interface {
 	// other namespace is specified and whether the namespace was
 	// overridden.
 	DefaultNamespace() (string, bool, error)
-	// Generators returns the generators for the provided command
-	Generators(cmdName string) map[string]kubectl.Generator
 
 	// Returns a RESTClient for working with the specified RESTMapping or an error. This is intended
 	// for working with arbitrary resources and is not guaranteed to point to a Kubernetes APIServer.

pkg/kubectl/cmd/util/factory_client_access.go

@@ -19,22 +19,11 @@ limitations under the License.
 package util
 
 import (
-	"fmt"
-	"io"
 	"sync"
 
-	appsv1 "k8s.io/api/apps/v1"
-	appsv1beta1 "k8s.io/api/apps/v1beta1"
-	batchv1 "k8s.io/api/batch/v1"
-	batchv1beta1 "k8s.io/api/batch/v1beta1"
-	batchv2alpha1 "k8s.io/api/batch/v2alpha1"
-	extensionsv1beta1 "k8s.io/api/extensions/v1beta1"
-	apierrors "k8s.io/apimachinery/pkg/api/errors"
 	"k8s.io/apimachinery/pkg/api/meta"
-	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
 	"k8s.io/apimachinery/pkg/runtime"
-	"k8s.io/apimachinery/pkg/runtime/schema"
 	"k8s.io/client-go/discovery"
 	"k8s.io/client-go/dynamic"
 	"k8s.io/client-go/kubernetes"
@@ -44,7 +33,6 @@ import (
 	"k8s.io/kubernetes/pkg/api/legacyscheme"
 	api "k8s.io/kubernetes/pkg/apis/core"
 	"k8s.io/kubernetes/pkg/client/clientset_generated/internalclientset"
-	"k8s.io/kubernetes/pkg/kubectl"
 	"k8s.io/kubernetes/pkg/kubectl/cmd/util/openapi"
 	openapivalidation "k8s.io/kubernetes/pkg/kubectl/cmd/util/openapi/validation"
 	"k8s.io/kubernetes/pkg/kubectl/genericclioptions"
@@ -223,216 +211,6 @@ func (f *factoryImpl) ScaleClient() (scaleclient.ScalesGetter, error) {
 	return scaleclient.New(restClient, mapper, dynamic.LegacyAPIPathResolverFunc, resolver), nil
 }
 
-const (
-	// TODO(sig-cli): Enforce consistent naming for generators here.
-	// See discussion in https://github.com/kubernetes/kubernetes/issues/46237
-	// before you add any more.
-	RunV1GeneratorName                      = "run/v1"
-	RunPodV1GeneratorName                   = "run-pod/v1"
-	ServiceV1GeneratorName                  = "service/v1"
-	ServiceV2GeneratorName                  = "service/v2"
-	ServiceNodePortGeneratorV1Name          = "service-nodeport/v1"
-	ServiceClusterIPGeneratorV1Name         = "service-clusterip/v1"
-	ServiceLoadBalancerGeneratorV1Name      = "service-loadbalancer/v1"
-	ServiceExternalNameGeneratorV1Name      = "service-externalname/v1"
-	ServiceAccountV1GeneratorName           = "serviceaccount/v1"
-	HorizontalPodAutoscalerV1GeneratorName  = "horizontalpodautoscaler/v1"
-	DeploymentV1Beta1GeneratorName          = "deployment/v1beta1"
-	DeploymentAppsV1Beta1GeneratorName      = "deployment/apps.v1beta1"
-	DeploymentBasicV1Beta1GeneratorName     = "deployment-basic/v1beta1"
-	DeploymentBasicAppsV1Beta1GeneratorName = "deployment-basic/apps.v1beta1"
-	DeploymentBasicAppsV1GeneratorName      = "deployment-basic/apps.v1"
-	JobV1GeneratorName                      = "job/v1"
-	CronJobV2Alpha1GeneratorName            = "cronjob/v2alpha1"
-	CronJobV1Beta1GeneratorName             = "cronjob/v1beta1"
-	NamespaceV1GeneratorName                = "namespace/v1"
-	ResourceQuotaV1GeneratorName            = "resourcequotas/v1"
-	SecretV1GeneratorName                   = "secret/v1"
-	SecretForDockerRegistryV1GeneratorName  = "secret-for-docker-registry/v1"
-	SecretForTLSV1GeneratorName             = "secret-for-tls/v1"
-	ConfigMapV1GeneratorName                = "configmap/v1"
-	ClusterRoleBindingV1GeneratorName       = "clusterrolebinding.rbac.authorization.k8s.io/v1alpha1"
-	RoleBindingV1GeneratorName              = "rolebinding.rbac.authorization.k8s.io/v1alpha1"
-	ClusterV1Beta1GeneratorName             = "cluster/v1beta1"
-	PodDisruptionBudgetV1GeneratorName      = "poddisruptionbudget/v1beta1"
-	PodDisruptionBudgetV2GeneratorName      = "poddisruptionbudget/v1beta1/v2"
-	PriorityClassV1Alpha1GeneratorName      = "priorityclass/v1alpha1"
-)
-
-// DefaultGenerators returns the set of default generators for use in Factory instances
-func DefaultGenerators(cmdName string) map[string]kubectl.Generator {
-	var generator map[string]kubectl.Generator
-	switch cmdName {
-	case "expose":
-		generator = map[string]kubectl.Generator{
-			ServiceV1GeneratorName: kubectl.ServiceGeneratorV1{},
-			ServiceV2GeneratorName: kubectl.ServiceGeneratorV2{},
-		}
-	case "service-clusterip":
-		generator = map[string]kubectl.Generator{
-			ServiceClusterIPGeneratorV1Name: kubectl.ServiceClusterIPGeneratorV1{},
-		}
-	case "service-nodeport":
-		generator = map[string]kubectl.Generator{
-			ServiceNodePortGeneratorV1Name: kubectl.ServiceNodePortGeneratorV1{},
-		}
-	case "service-loadbalancer":
-		generator = map[string]kubectl.Generator{
-			ServiceLoadBalancerGeneratorV1Name: kubectl.ServiceLoadBalancerGeneratorV1{},
-		}
-	case "deployment":
-		// Create Deployment has only StructuredGenerators and no
-		// param-based Generators.
-		// The StructuredGenerators are as follows (as of 2018-03-16):
-		// DeploymentBasicV1Beta1GeneratorName -> kubectl.DeploymentBasicGeneratorV1
-		// DeploymentBasicAppsV1Beta1GeneratorName -> kubectl.DeploymentBasicAppsGeneratorV1Beta1
-		// DeploymentBasicAppsV1GeneratorName -> kubectl.DeploymentBasicAppsGeneratorV1
-		generator = map[string]kubectl.Generator{}
-	case "run":
-		generator = map[string]kubectl.Generator{
-			RunV1GeneratorName:                 kubectl.BasicReplicationController{},
-			RunPodV1GeneratorName:              kubectl.BasicPod{},
-			DeploymentV1Beta1GeneratorName:     kubectl.DeploymentV1Beta1{},
-			DeploymentAppsV1Beta1GeneratorName: kubectl.DeploymentAppsV1Beta1{},
-			JobV1GeneratorName:                 kubectl.JobV1{},
-			CronJobV2Alpha1GeneratorName:       kubectl.CronJobV2Alpha1{},
-			CronJobV1Beta1GeneratorName:        kubectl.CronJobV1Beta1{},
-		}
-	case "namespace":
-		generator = map[string]kubectl.Generator{
-			NamespaceV1GeneratorName: kubectl.NamespaceGeneratorV1{},
-		}
-	case "quota":
-		generator = map[string]kubectl.Generator{
-			ResourceQuotaV1GeneratorName: kubectl.ResourceQuotaGeneratorV1{},
-		}
-	case "secret":
-		generator = map[string]kubectl.Generator{
-			SecretV1GeneratorName: kubectl.SecretGeneratorV1{},
-		}
-	case "secret-for-docker-registry":
-		generator = map[string]kubectl.Generator{
-			SecretForDockerRegistryV1GeneratorName: kubectl.SecretForDockerRegistryGeneratorV1{},
-		}
-	case "secret-for-tls":
-		generator = map[string]kubectl.Generator{
-			SecretForTLSV1GeneratorName: kubectl.SecretForTLSGeneratorV1{},
-		}
-	}
-
-	return generator
-}
-
-// fallbackGeneratorNameIfNecessary returns the name of the old generator
-// if server does not support new generator. Otherwise, the
-// generator string is returned unchanged.
-//
-// If the generator name is changed, print a warning message to let the user
-// know.
-func FallbackGeneratorNameIfNecessary(
-	generatorName string,
-	discoveryClient discovery.DiscoveryInterface,
-	cmdErr io.Writer,
-) (string, error) {
-	switch generatorName {
-	case DeploymentAppsV1Beta1GeneratorName:
-		hasResource, err := HasResource(discoveryClient, appsv1beta1.SchemeGroupVersion.WithResource("deployments"))
-		if err != nil {
-			return "", err
-		}
-		if !hasResource {
-			return FallbackGeneratorNameIfNecessary(DeploymentV1Beta1GeneratorName, discoveryClient, cmdErr)
-		}
-	case DeploymentV1Beta1GeneratorName:
-		hasResource, err := HasResource(discoveryClient, extensionsv1beta1.SchemeGroupVersion.WithResource("deployments"))
-		if err != nil {
-			return "", err
-		}
-		if !hasResource {
-			return RunV1GeneratorName, nil
-		}
-	case DeploymentBasicAppsV1GeneratorName:
-		hasResource, err := HasResource(discoveryClient, appsv1.SchemeGroupVersion.WithResource("deployments"))
-		if err != nil {
-			return "", err
-		}
-		if !hasResource {
-			return FallbackGeneratorNameIfNecessary(DeploymentBasicAppsV1Beta1GeneratorName, discoveryClient, cmdErr)
-		}
-	case DeploymentBasicAppsV1Beta1GeneratorName:
-		hasResource, err := HasResource(discoveryClient, appsv1beta1.SchemeGroupVersion.WithResource("deployments"))
-		if err != nil {
-			return "", err
-		}
-		if !hasResource {
-			return DeploymentBasicV1Beta1GeneratorName, nil
-		}
-	case JobV1GeneratorName:
-		hasResource, err := HasResource(discoveryClient, batchv1.SchemeGroupVersion.WithResource("jobs"))
-		if err != nil {
-			return "", err
-		}
-		if !hasResource {
-			return RunPodV1GeneratorName, nil
-		}
-	case CronJobV1Beta1GeneratorName:
-		hasResource, err := HasResource(discoveryClient, batchv1beta1.SchemeGroupVersion.WithResource("cronjobs"))
-		if err != nil {
-			return "", err
-		}
-		if !hasResource {
-			return FallbackGeneratorNameIfNecessary(CronJobV2Alpha1GeneratorName, discoveryClient, cmdErr)
-		}
-	case CronJobV2Alpha1GeneratorName:
-		hasResource, err := HasResource(discoveryClient, batchv2alpha1.SchemeGroupVersion.WithResource("cronjobs"))
-		if err != nil {
-			return "", err
-		}
-		if !hasResource {
-			return JobV1GeneratorName, nil
-		}
-	}
-	return generatorName, nil
-}
-
-func Warning(cmdErr io.Writer, newGeneratorName, oldGeneratorName string) {
-	fmt.Fprintf(cmdErr, "WARNING: New generator %q specified, "+
-		"but it isn't available. "+
-		"Falling back to %q.\n",
-		newGeneratorName,
-		oldGeneratorName,
-	)
-}
-
-func HasResource(client discovery.DiscoveryInterface, resource schema.GroupVersionResource) (bool, error) {
-	resources, err := client.ServerResourcesForGroupVersion(resource.GroupVersion().String())
-	if apierrors.IsNotFound(err) {
-		// entire group is missing
-		return false, nil
-	}
-	if err != nil {
-		// other errors error
-		return false, fmt.Errorf("failed to discover supported resources: %v", err)
-	}
-	for _, serverResource := range resources.APIResources {
-		if serverResource.Name == resource.Resource {
-			return true, nil
-		}
-	}
-	return false, nil
-}
-
-func Contains(resourcesList []*metav1.APIResourceList, resource schema.GroupVersionResource) bool {
-	resources := discovery.FilteredBy(discovery.ResourcePredicateFunc(func(gv string, r *metav1.APIResource) bool {
-		return resource.GroupVersion().String() == gv && resource.Resource == r.Name
-	}), resourcesList)
-	return len(resources) != 0
-}
-
-func (f *factoryImpl) Generators(cmdName string) map[string]kubectl.Generator {
-	return DefaultGenerators(cmdName)
-}
-
 // this method exists to help us find the points still relying on internal types.
 func InternalVersionDecoder() runtime.Decoder {
 	return legacyscheme.Codecs.UniversalDecoder()

pkg/kubectl/cmd/util/generator.go

+/*
+Copyright 2018 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package util
+
+import (
+	"fmt"
+	"io"
+
+	appsv1 "k8s.io/api/apps/v1"
+	appsv1beta1 "k8s.io/api/apps/v1beta1"
+	batchv1 "k8s.io/api/batch/v1"
+	batchv1beta1 "k8s.io/api/batch/v1beta1"
+	batchv2alpha1 "k8s.io/api/batch/v2alpha1"
+	extensionsv1beta1 "k8s.io/api/extensions/v1beta1"
+	apierrors "k8s.io/apimachinery/pkg/api/errors"
+	"k8s.io/apimachinery/pkg/runtime/schema"
+	"k8s.io/client-go/discovery"
+	"k8s.io/kubernetes/pkg/kubectl"
+)
+
+const (
+	// TODO(sig-cli): Enforce consistent naming for generators here.
+	// See discussion in https://github.com/kubernetes/kubernetes/issues/46237
+	// before you add any more.
+	RunV1GeneratorName                      = "run/v1"
+	RunPodV1GeneratorName                   = "run-pod/v1"
+	ServiceV1GeneratorName                  = "service/v1"
+	ServiceV2GeneratorName                  = "service/v2"
+	ServiceNodePortGeneratorV1Name          = "service-nodeport/v1"
+	ServiceClusterIPGeneratorV1Name         = "service-clusterip/v1"
+	ServiceLoadBalancerGeneratorV1Name      = "service-loadbalancer/v1"
+	ServiceExternalNameGeneratorV1Name      = "service-externalname/v1"
+	ServiceAccountV1GeneratorName           = "serviceaccount/v1"
+	HorizontalPodAutoscalerV1GeneratorName  = "horizontalpodautoscaler/v1"
+	DeploymentV1Beta1GeneratorName          = "deployment/v1beta1"
+	DeploymentAppsV1Beta1GeneratorName      = "deployment/apps.v1beta1"
+	DeploymentBasicV1Beta1GeneratorName     = "deployment-basic/v1beta1"
+	DeploymentBasicAppsV1Beta1GeneratorName = "deployment-basic/apps.v1beta1"
+	DeploymentBasicAppsV1GeneratorName      = "deployment-basic/apps.v1"
+	JobV1GeneratorName                      = "job/v1"
+	CronJobV2Alpha1GeneratorName            = "cronjob/v2alpha1"
+	CronJobV1Beta1GeneratorName             = "cronjob/v1beta1"
+	NamespaceV1GeneratorName                = "namespace/v1"
+	ResourceQuotaV1GeneratorName            = "resourcequotas/v1"
+	SecretV1GeneratorName                   = "secret/v1"
+	SecretForDockerRegistryV1GeneratorName  = "secret-for-docker-registry/v1"
+	SecretForTLSV1GeneratorName             = "secret-for-tls/v1"
+	ConfigMapV1GeneratorName                = "configmap/v1"
+	ClusterRoleBindingV1GeneratorName       = "clusterrolebinding.rbac.authorization.k8s.io/v1alpha1"
+	RoleBindingV1GeneratorName              = "rolebinding.rbac.authorization.k8s.io/v1alpha1"
+	ClusterV1Beta1GeneratorName             = "cluster/v1beta1"
+	PodDisruptionBudgetV1GeneratorName      = "poddisruptionbudget/v1beta1"
+	PodDisruptionBudgetV2GeneratorName      = "poddisruptionbudget/v1beta1/v2"
+	PriorityClassV1Alpha1GeneratorName      = "priorityclass/v1alpha1"
+)
+
+// GeneratorFunc returns the generators for the provided command
+type GeneratorFunc func(cmdName string) map[string]kubectl.Generator
+
+// GeneratorFn gives a way to easily override the function for unit testing if needed
+var GeneratorFn GeneratorFunc = defaultGenerators
+
+// defaultGenerators returns the set of default generators for use in Factory instances
+func defaultGenerators(cmdName string) map[string]kubectl.Generator {
+	var generator map[string]kubectl.Generator
+	switch cmdName {
+	case "expose":
+		generator = map[string]kubectl.Generator{
+			ServiceV1GeneratorName: kubectl.ServiceGeneratorV1{},
+			ServiceV2GeneratorName: kubectl.ServiceGeneratorV2{},
+		}
+	case "service-clusterip":
+		generator = map[string]kubectl.Generator{
+			ServiceClusterIPGeneratorV1Name: kubectl.ServiceClusterIPGeneratorV1{},
+		}
+	case "service-nodeport":
+		generator = map[string]kubectl.Generator{
+			ServiceNodePortGeneratorV1Name: kubectl.ServiceNodePortGeneratorV1{},
+		}
+	case "service-loadbalancer":
+		generator = map[string]kubectl.Generator{
+			ServiceLoadBalancerGeneratorV1Name: kubectl.ServiceLoadBalancerGeneratorV1{},
+		}
+	case "deployment":
+		// Create Deployment has only StructuredGenerators and no
+		// param-based Generators.
+		// The StructuredGenerators are as follows (as of 2018-03-16):
+		// DeploymentBasicV1Beta1GeneratorName -> kubectl.DeploymentBasicGeneratorV1
+		// DeploymentBasicAppsV1Beta1GeneratorName -> kubectl.DeploymentBasicAppsGeneratorV1Beta1
+		// DeploymentBasicAppsV1GeneratorName -> kubectl.DeploymentBasicAppsGeneratorV1
+		generator = map[string]kubectl.Generator{}
+	case "run":
+		generator = map[string]kubectl.Generator{
+			RunV1GeneratorName:                 kubectl.BasicReplicationController{},
+			RunPodV1GeneratorName:              kubectl.BasicPod{},
+			DeploymentV1Beta1GeneratorName:     kubectl.DeploymentV1Beta1{},
+			DeploymentAppsV1Beta1GeneratorName: kubectl.DeploymentAppsV1Beta1{},
+			JobV1GeneratorName:                 kubectl.JobV1{},
+			CronJobV2Alpha1GeneratorName:       kubectl.CronJobV2Alpha1{},
+			CronJobV1Beta1GeneratorName:        kubectl.CronJobV1Beta1{},
+		}
+	case "namespace":
+		generator = map[string]kubectl.Generator{
+			NamespaceV1GeneratorName: kubectl.NamespaceGeneratorV1{},
+		}
+	case "quota":
+		generator = map[string]kubectl.Generator{
+			ResourceQuotaV1GeneratorName: kubectl.ResourceQuotaGeneratorV1{},
+		}
+	case "secret":
+		generator = map[string]kubectl.Generator{
+			SecretV1GeneratorName: kubectl.SecretGeneratorV1{},
+		}
+	case "secret-for-docker-registry":
+		generator = map[string]kubectl.Generator{
+			SecretForDockerRegistryV1GeneratorName: kubectl.SecretForDockerRegistryGeneratorV1{},
+		}
+	case "secret-for-tls":
+		generator = map[string]kubectl.Generator{
+			SecretForTLSV1GeneratorName: kubectl.SecretForTLSGeneratorV1{},
+		}
+	}
+
+	return generator
+}
+
+// FallbackGeneratorNameIfNecessary returns the name of the old generator
+// if server does not support new generator. Otherwise, the
+// generator string is returned unchanged.
+//
+// If the generator name is changed, print a warning message to let the user
+// know.
+func FallbackGeneratorNameIfNecessary(
+	generatorName string,
+	discoveryClient discovery.DiscoveryInterface,
+	cmdErr io.Writer,
+) (string, error) {
+	switch generatorName {
+	case DeploymentAppsV1Beta1GeneratorName:
+		hasResource, err := HasResource(discoveryClient, appsv1beta1.SchemeGroupVersion.WithResource("deployments"))
+		if err != nil {
+			return "", err
+		}
+		if !hasResource {
+			return FallbackGeneratorNameIfNecessary(DeploymentV1Beta1GeneratorName, discoveryClient, cmdErr)
+		}
+	case DeploymentV1Beta1GeneratorName:
+		hasResource, err := HasResource(discoveryClient, extensionsv1beta1.SchemeGroupVersion.WithResource("deployments"))
+		if err != nil {
+			return "", err
+		}
+		if !hasResource {
+			return RunV1GeneratorName, nil
+		}
+	case DeploymentBasicAppsV1GeneratorName:
+		hasResource, err := HasResource(discoveryClient, appsv1.SchemeGroupVersion.WithResource("deployments"))
+		if err != nil {
+			return "", err
+		}
+		if !hasResource {
+			return FallbackGeneratorNameIfNecessary(DeploymentBasicAppsV1Beta1GeneratorName, discoveryClient, cmdErr)
+		}
+	case DeploymentBasicAppsV1Beta1GeneratorName:
+		hasResource, err := HasResource(discoveryClient, appsv1beta1.SchemeGroupVersion.WithResource("deployments"))
+		if err != nil {
+			return "", err
+		}
+		if !hasResource {
+			return DeploymentBasicV1Beta1GeneratorName, nil
+		}
+	case JobV1GeneratorName:
+		hasResource, err := HasResource(discoveryClient, batchv1.SchemeGroupVersion.WithResource("jobs"))
+		if err != nil {
+			return "", err
+		}
+		if !hasResource {
+			return RunPodV1GeneratorName, nil
+		}
+	case CronJobV1Beta1GeneratorName:
+		hasResource, err := HasResource(discoveryClient, batchv1beta1.SchemeGroupVersion.WithResource("cronjobs"))
+		if err != nil {
+			return "", err
+		}
+		if !hasResource {
+			return FallbackGeneratorNameIfNecessary(CronJobV2Alpha1GeneratorName, discoveryClient, cmdErr)
+		}
+	case CronJobV2Alpha1GeneratorName:
+		hasResource, err := HasResource(discoveryClient, batchv2alpha1.SchemeGroupVersion.WithResource("cronjobs"))
+		if err != nil {
+			return "", err
+		}
+		if !hasResource {
+			return JobV1GeneratorName, nil
+		}
+	}
+	return generatorName, nil
+}
+
+func HasResource(client discovery.DiscoveryInterface, resource schema.GroupVersionResource) (bool, error) {
+	resources, err := client.ServerResourcesForGroupVersion(resource.GroupVersion().String())
+	if apierrors.IsNotFound(err) {
+		// entire group is missing
+		return false, nil
+	}
+	if err != nil {
+		// other errors error
+		return false, fmt.Errorf("failed to discover supported resources: %v", err)
+	}
+	for _, serverResource := range resources.APIResources {
+		if serverResource.Name == resource.Resource {
+			return true, nil
+		}
+	}
+	return false, nil
+}
+
+func Warning(cmdErr io.Writer, newGeneratorName, oldGeneratorName string) {
+	fmt.Fprintf(cmdErr, "WARNING: New generator %q specified, "+
+		"but it isn't available. "+
+		"Falling back to %q.\n",
+		newGeneratorName,
+		oldGeneratorName,
+	)
+}