Fixing the error message

docs/man/man1/kubectl-expose.1

@@ -68,7 +68,7 @@ re\-use the labels from the resource it exposes.
 
 .PP
 \fB\-\-port\fP=\-1
-    The port that the service should serve on. Required.
+    The port that the service should serve on. Copied from the resource being exposed, if unspecified
 
 .PP
 \fB\-\-protocol\fP="TCP"

docs/user-guide/kubectl/kubectl_expose.md

@@ -64,7 +64,7 @@ $ kubectl expose rc streamer --port=4100 --protocol=udp --name=video-stream
   -o, --output="": Output format. One of: json|yaml|template|templatefile|wide.
       --output-version="": Output the formatted object with the given version (default api-version).
       --overrides="": An inline JSON override for the generated object. If this is non-empty, it is used to override the generated object. Requires that the object supply a valid apiVersion field.
-      --port=-1: The port that the service should serve on. Required.
+      --port=-1: The port that the service should serve on. Copied from the resource being exposed, if unspecified
       --protocol="TCP": The network protocol for the service to be created. Default is 'tcp'.
       --public-ip="": Name of a public IP address to set for the service. The service will be assigned this IP in addition to its generated service IP.
       --selector="": A label selector to use for this service. If empty (the default) infer the selector from the replication controller.
@@ -105,7 +105,7 @@ $ kubectl expose rc streamer --port=4100 --protocol=udp --name=video-stream
 ### SEE ALSO
 * [kubectl](kubectl.md)	 - kubectl controls the Kubernetes cluster manager
 
-###### Auto generated by spf13/cobra at 2015-07-16 21:22:36.08263026 +0000 UTC
+###### Auto generated by spf13/cobra at 2015-07-17 01:17:57.020108348 +0000 UTC
 
 
 <!-- BEGIN MUNGE: GENERATED_ANALYTICS -->

pkg/kubectl/cmd/expose.go

@@ -58,7 +58,7 @@ func NewCmdExposeService(f *cmdutil.Factory, out io.Writer) *cobra.Command {
 	cmdutil.AddPrinterFlags(cmd)
 	cmd.Flags().String("generator", "service/v2", "The name of the API generator to use. There are 2 generators: 'service/v1' and 'service/v2'. The only difference between them is that service port in v1 is named 'default', while it is left unnamed in v2. Default is 'service/v2'.")
 	cmd.Flags().String("protocol", "TCP", "The network protocol for the service to be created. Default is 'tcp'.")
-	cmd.Flags().Int("port", -1, "The port that the service should serve on. Required.")
+	cmd.Flags().Int("port", -1, "The port that the service should serve on. Copied from the resource being exposed, if unspecified")
 	cmd.MarkFlagRequired("port")
 	cmd.Flags().String("type", "", "Type for this service: ClusterIP, NodePort, or LoadBalancer. Default is 'ClusterIP' unless --create-external-load-balancer is specified.")
 	cmd.Flags().Bool("create-external-load-balancer", false, "If true, create an external load balancer for this service (trumped by --type). Implementation is cloud provider dependent. Default is 'false'.")
@@ -126,7 +126,7 @@ func RunExpose(f *cmdutil.Factory, out io.Writer, cmd *cobra.Command, args []str
 		if len(s) == 0 {
 			s, err := f.PodSelectorForObject(inputObject)
 			if err != nil {
-				return err
+				return cmdutil.UsageError(cmd, fmt.Sprintf("couldn't find selectors via --selector flag or introspection: %s", err))
 			}
 			params["selector"] = s
 		}
@@ -140,15 +140,15 @@ func RunExpose(f *cmdutil.Factory, out io.Writer, cmd *cobra.Command, args []str
 		if cmdutil.GetFlagInt(cmd, "port") < 0 && !noPorts {
 			ports, err := f.PortsForObject(inputObject)
 			if err != nil {
-				return err
+				return cmdutil.UsageError(cmd, fmt.Sprintf("couldn't find port via --port flag or introspection: %s", err))
 			}
 			switch len(ports) {
 			case 0:
-				return cmdutil.UsageError(cmd, "couldn't find a suitable port via --port flag or introspection")
+				return cmdutil.UsageError(cmd, "couldn't find port via --port flag or introspection")
 			case 1:
 				params["port"] = ports[0]
 			default:
-				return cmdutil.UsageError(cmd, "more than one port to choose from, please explicitly specify a port using the --port flag.")
+				return cmdutil.UsageError(cmd, fmt.Sprintf("multiple ports to choose from: %v, please explicitly specify a port using the --port flag.", ports))
 			}
 		}
 	}

pkg/kubectl/cmd/util/factory.go

@@ -163,11 +163,11 @@ func NewFactory(optionalClientConfig clientcmd.ClientConfig) *Factory {
 				}
 				return kubectl.MakeLabels(t.Spec.Selector), nil
 			default:
-				kind, err := meta.NewAccessor().Kind(object)
+				_, kind, err := api.Scheme.ObjectVersionAndKind(object)
 				if err != nil {
 					return "", err
 				}
-				return "", fmt.Errorf("it is not possible to get a pod selector from %s", kind)
+				return "", fmt.Errorf("cannot extract pod selector from %s", kind)
 			}
 		},
 		PortsForObject: func(object runtime.Object) ([]string, error) {
@@ -178,11 +178,13 @@ func NewFactory(optionalClientConfig clientcmd.ClientConfig) *Factory {
 			case *api.Pod:
 				return getPorts(t.Spec), nil
 			default:
-				kind, err := meta.NewAccessor().Kind(object)
+				// TODO: support extracting ports from service:
+				// https://github.com/GoogleCloudPlatform/kubernetes/issues/11392
+				_, kind, err := api.Scheme.ObjectVersionAndKind(object)
 				if err != nil {
 					return nil, err
 				}
-				return nil, fmt.Errorf("it is not possible to get ports from %s", kind)
+				return nil, fmt.Errorf("cannot extract ports from %s", kind)
 			}
 		},
 		LabelsForObject: func(object runtime.Object) (map[string]string, error) {