describe: allow describing generic api objects

pkg/kubectl/cmd/util/factory_object_mapping.go

@@ -158,14 +158,55 @@ func (f *ring1Factory) Describer(mapping *meta.RESTMapping) (kubectl.Describer,
 			return &kubectl.ClusterDescriber{Interface: fedClientSet}, nil
 		}
 	}
+
 	clientset, err := f.clientAccessFactory.ClientSetForVersion(&mappingVersion)
 	if err != nil {
+		// if we can't make a client for this group/version, go generic if possible
+		if genericDescriber, genericErr := genericDescriber(f.clientAccessFactory, mapping); genericErr == nil {
+			return genericDescriber, nil
+		}
+		// otherwise return the original error
 		return nil, err
 	}
+
+	// try to get a describer
 	if describer, ok := kubectl.DescriberFor(mapping.GroupVersionKind.GroupKind(), clientset); ok {
 		return describer, nil
 	}
-	return nil, fmt.Errorf("no description has been implemented for %q", mapping.GroupVersionKind.Kind)
+	// if this is a kind we don't have a describer for yet, go generic if possible
+	if genericDescriber, genericErr := genericDescriber(f.clientAccessFactory, mapping); genericErr == nil {
+		return genericDescriber, nil
+	}
+	// otherwise return an unregistered error
+	return nil, fmt.Errorf("no description has been implemented for %s", mapping.GroupVersionKind.String())
+}
+
+// helper function to make a generic describer, or return an error
+func genericDescriber(clientAccessFactory ClientAccessFactory, mapping *meta.RESTMapping) (kubectl.Describer, error) {
+	clientConfig, err := clientAccessFactory.ClientConfig()
+	if err != nil {
+		return nil, err
+	}
+
+	clientConfigCopy := *clientConfig
+	clientConfigCopy.APIPath = dynamic.LegacyAPIPathResolverFunc(mapping.GroupVersionKind)
+	gv := mapping.GroupVersionKind.GroupVersion()
+	clientConfigCopy.GroupVersion = &gv
+
+	// used to fetch the resource
+	dynamicClient, err := dynamic.NewClient(&clientConfigCopy)
+	if err != nil {
+		return nil, err
+	}
+
+	// used to get events for the resource
+	clientSet, err := clientAccessFactory.ClientSet()
+	if err != nil {
+		return nil, err
+	}
+	eventsClient := clientSet.Core()
+
+	return kubectl.GenericDescriberFor(mapping, dynamicClient, eventsClient), nil
 }
 
 func (f *ring1Factory) LogsForObject(object, options runtime.Object) (*restclient.Request, error) {

pkg/kubectl/describe.go

@@ -29,12 +29,14 @@ import (
 	"time"
 
 	"k8s.io/apimachinery/pkg/api/errors"
+	"k8s.io/apimachinery/pkg/api/meta"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/fields"
 	"k8s.io/apimachinery/pkg/labels"
 	"k8s.io/apimachinery/pkg/runtime/schema"
 	"k8s.io/apimachinery/pkg/types"
 	"k8s.io/apimachinery/pkg/util/sets"
+	"k8s.io/client-go/dynamic"
 	"k8s.io/kubernetes/federation/apis/federation"
 	fedclientset "k8s.io/kubernetes/federation/client/clientset_generated/federation_internalclientset"
 	"k8s.io/kubernetes/pkg/api"
@@ -171,6 +173,46 @@ func DescriberFor(kind schema.GroupKind, c clientset.Interface) (Describer, bool
 	return f, ok
 }
 
+// GenericDescriberFor returns a generic describer for the specified mapping
+// that uses only information available from runtime.Unstructured
+func GenericDescriberFor(mapping *meta.RESTMapping, dynamic *dynamic.Client, events coreclient.EventsGetter) Describer {
+	return &genericDescriber{mapping, dynamic, events}
+}
+
+type genericDescriber struct {
+	mapping *meta.RESTMapping
+	dynamic *dynamic.Client
+	events  coreclient.EventsGetter
+}
+
+func (g *genericDescriber) Describe(namespace, name string, describerSettings DescriberSettings) (output string, err error) {
+	apiResource := &metav1.APIResource{
+		Name:       g.mapping.Resource,
+		Namespaced: g.mapping.Scope.Name() == meta.RESTScopeNameNamespace,
+		Kind:       g.mapping.GroupVersionKind.Kind,
+	}
+	obj, err := g.dynamic.Resource(apiResource, namespace).Get(name)
+	if err != nil {
+		return "", err
+	}
+
+	var events *api.EventList
+	if describerSettings.ShowEvents {
+		events, _ = g.events.Events(namespace).Search(obj)
+	}
+
+	return tabbedString(func(out io.Writer) error {
+		w := &PrefixWriter{out}
+		w.Write(LEVEL_0, "Name:\t%s\n", obj.GetName())
+		w.Write(LEVEL_0, "Namespace:\t%s\n", obj.GetNamespace())
+		printLabelsMultiline(w, "Labels", obj.GetLabels())
+		if events != nil {
+			DescribeEvents(events, w)
+		}
+		return nil
+	})
+}
+
 // DefaultObjectDescriber can describe the default Kubernetes objects.
 var DefaultObjectDescriber ObjectDescriber