Limit the type for kubectl expose command

pkg/kubectl/cmd/cmd_test.go

@@ -227,15 +227,19 @@ func NewAPIFactory() (*cmdutil.Factory, *testFactory, runtime.Codec) {
 		ClientConfig: func() (*client.Config, error) {
 			return t.ClientConfig, t.Err
 		},
+		CanBeExposed: func(kind string) error {
+			if kind != "ReplicationController" && kind != "Service" && kind != "Pod" {
+				return fmt.Errorf("invalid resource provided: %v, only a replication controller, service or pod is accepted", kind)
+			}
+			return nil
+		},
 		Generator: func(name string) (kubectl.Generator, bool) {
 			generator, ok := generators[name]
 			return generator, ok
 		},
 	}
-
 	rf := cmdutil.NewFactory(nil)
 	f.PodSelectorForObject = rf.PodSelectorForObject
-
 	return f, t, testapi.Default.Codec()
 }
 

pkg/kubectl/cmd/expose.go

@@ -34,9 +34,9 @@ type ExposeOptions struct {
 }
 
 const (
-	expose_long = `Take a replicated application and expose it as Kubernetes Service.
+	expose_long = `Take a replication controller, service or pod and expose it as a new Kubernetes Service.
 
-Looks up a replication controller or service by name and uses the selector for that resource as the
+Looks up a replication controller, service or pod by name and uses the selector for that resource as the
 selector for a new Service on the specified port. If no labels are specified, the new service will
 re-use the labels from the resource it exposes.`
 
@@ -46,6 +46,9 @@ $ kubectl expose rc nginx --port=80 --target-port=8000
 # Create a service for a replication controller identified by type and name specified in "nginx-controller.yaml", which serves on port 80 and connects to the containers on port 8000.
 $ kubectl expose -f nginx-controller.yaml --port=80 --target-port=8000
 
+# Create a service for a pod valid-pod, which serves on port 444 with the name "frontend"
+$ kubectl expose pod valid-pod --port=444 --name=frontend
+
 # Create a second service based on the above service, exposing the container port 8443 as port 443 with the name "nginx-https"
 $ kubectl expose service nginx --port=443 --target-port=8443 --name=nginx-https
 
@@ -58,7 +61,7 @@ func NewCmdExposeService(f *cmdutil.Factory, out io.Writer) *cobra.Command {
 
 	cmd := &cobra.Command{
 		Use:     "expose (-f FILENAME | TYPE NAME) [--port=port] [--protocol=TCP|UDP] [--target-port=number-or-name] [--name=name] [----external-ip=external-ip-of-service] [--type=type]",
-		Short:   "Take a replicated application and expose it as Kubernetes Service",
+		Short:   "Take a replication controller, service or pod and expose it as a new Kubernetes Service",
 		Long:    expose_long,
 		Example: expose_example,
 		Run: func(cmd *cobra.Command, args []string) {
@@ -113,7 +116,9 @@ func RunExpose(f *cmdutil.Factory, out io.Writer, cmd *cobra.Command, args []str
 	}
 	info := infos[0]
 	mapping := info.ResourceMapping()
-
+	if err := f.CanBeExposed(mapping.Kind); err != nil {
+		return err
+	}
 	// Get the input object
 	inputObject, err := r.Object()
 	if err != nil {

pkg/kubectl/cmd/util/factory.go

@@ -86,6 +86,8 @@ type Factory struct {
 	DefaultNamespace func() (string, bool, error)
 	// Returns the generator for the provided generator name
 	Generator func(name string) (kubectl.Generator, bool)
+	// Check whether the kind of resources could be exposed
+	CanBeExposed func(kind string) error
 }
 
 // NewFactory creates a factory with the default Kubernetes resources defined
@@ -246,6 +248,12 @@ func NewFactory(optionalClientConfig clientcmd.ClientConfig) *Factory {
 			generator, ok := generators[name]
 			return generator, ok
 		},
+		CanBeExposed: func(kind string) error {
+			if kind != "ReplicationController" && kind != "Service" && kind != "Pod" {
+				return fmt.Errorf("invalid resource provided: %v, only a replication controller, service or pod is accepted", kind)
+			}
+			return nil
+		},
 	}
 }
 

pkg/kubectl/cmd/util/factory_test.go

@@ -165,6 +165,33 @@ func TestLabelsForObject(t *testing.T) {
 	}
 }
 
+func TestCanBeExposed(t *testing.T) {
+	factory := NewFactory(nil)
+	tests := []struct {
+		kind      string
+		expectErr bool
+	}{
+		{
+			kind:      "ReplicationController",
+			expectErr: false,
+		},
+		{
+			kind:      "Node",
+			expectErr: true,
+		},
+	}
+
+	for _, test := range tests {
+		err := factory.CanBeExposed(test.kind)
+		if test.expectErr && err == nil {
+			t.Error("unexpected non-error")
+		}
+		if !test.expectErr && err != nil {
+			t.Errorf("unexpected error: %v", err)
+		}
+	}
+}
+
 func TestFlagUnderscoreRenaming(t *testing.T) {
 	factory := NewFactory(nil)