Merge pull request #53606 from juanvallejo/jvallejo/add-approx-pod-template-factory-method

Automatic merge from submit-queue (batch tested with PRs 53606, 49361). If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

add ApproximatePodTemplateForObject factory method

Makes it possible to get at a pod spec template even if an object is scaled to zero, for use with commands that care about pod templates.

**Release note**:

```release-note
NONE
```

Related downstream patch and use-case: https://github.com/openshift/origin/pull/16379

cc @smarterclayton

pkg/kubectl/cmd/testing/fake.go

@@ -449,6 +449,10 @@ func (f *FakeFactory) AttachablePodForObject(ob runtime.Object, timeout time.Dur
 	return nil, nil
 }
 
+func (f *FakeFactory) ApproximatePodTemplateForObject(obj runtime.Object) (*api.PodTemplateSpec, error) {
+	return f.ApproximatePodTemplateForObject(obj)
+}
+
 func (f *FakeFactory) UpdatePodSpecForObject(obj runtime.Object, fn func(*api.PodSpec) error) (bool, error) {
 	return false, nil
 }
@@ -713,6 +717,10 @@ func (f *fakeAPIFactory) AttachablePodForObject(object runtime.Object, timeout t
 	}
 }
 
+func (f *fakeAPIFactory) ApproximatePodTemplateForObject(obj runtime.Object) (*api.PodTemplateSpec, error) {
+	return f.Factory.ApproximatePodTemplateForObject(obj)
+}
+
 func (f *fakeAPIFactory) Validator(validate bool) (validation.Schema, error) {
 	return f.tf.Validator, f.tf.Err
 }

pkg/kubectl/cmd/util/factory.go

@@ -223,6 +223,11 @@ type ObjectMappingFactory interface {
 	// AttachablePodForObject returns the pod to which to attach given an object.
 	AttachablePodForObject(object runtime.Object, timeout time.Duration) (*api.Pod, error)
 
+	// ApproximatePodTemplateForObject returns a pod template object for the provided source.
+	// It may return both an error and a object. It attempt to return the best possible template
+	// available at the current time.
+	ApproximatePodTemplateForObject(runtime.Object) (*api.PodTemplateSpec, error)
+
 	// Returns a schema that can validate objects stored on disk.
 	Validator(validate bool) (validation.Schema, error)
 	// OpenAPISchema returns the schema openapi schema definiton

pkg/kubectl/cmd/util/factory_object_mapping.go

@@ -22,6 +22,7 @@ import (
 	"errors"
 	"fmt"
 	"os"
+	"reflect"
 	"sort"
 	"sync"
 	"time"
@@ -351,6 +352,28 @@ func (f *ring1Factory) StatusViewer(mapping *meta.RESTMapping) (kubectl.StatusVi
 	return kubectl.StatusViewerFor(mapping.GroupVersionKind.GroupKind(), clientset)
 }
 
+func (f *ring1Factory) ApproximatePodTemplateForObject(object runtime.Object) (*api.PodTemplateSpec, error) {
+	switch t := object.(type) {
+	case *api.Pod:
+		return &api.PodTemplateSpec{
+			ObjectMeta: t.ObjectMeta,
+			Spec:       t.Spec,
+		}, nil
+	case *api.ReplicationController:
+		return t.Spec.Template, nil
+	case *extensions.ReplicaSet:
+		return &t.Spec.Template, nil
+	case *extensions.DaemonSet:
+		return &t.Spec.Template, nil
+	case *extensions.Deployment:
+		return &t.Spec.Template, nil
+	case *batch.Job:
+		return &t.Spec.Template, nil
+	}
+
+	return nil, fmt.Errorf("unable to extract pod template from type %v", reflect.TypeOf(object))
+}
+
 func (f *ring1Factory) AttachablePodForObject(object runtime.Object, timeout time.Duration) (*api.Pod, error) {
 	clientset, err := f.clientAccessFactory.ClientSetForVersion(nil)
 	if err != nil {