add check to NewCmdExec before printing suggestion

checks that the "describe" command and a parent command path exist
before printing suggestion to use the describe command to list
containers in a pod.

pkg/kubectl/cmd/cmd.go

@@ -287,7 +287,7 @@ Find more information at https://github.com/kubernetes/kubernetes.`,
 				NewCmdDescribe(f, out, err),
 				NewCmdLogs(f, out),
 				NewCmdAttach(f, in, out, err),
-				NewCmdExec(cmds.Root().CommandPath(), f, in, out, err),
+				NewCmdExec(f, in, out, err),
 				NewCmdPortForward(f, out, err),
 				NewCmdProxy(f, out),
 			},

pkg/kubectl/cmd/exec.go

@@ -52,7 +52,7 @@ const (
 	execUsageStr = "expected 'exec POD_NAME COMMAND [ARG1] [ARG2] ... [ARGN]'.\nPOD_NAME and COMMAND are required arguments for the exec command"
 )
 
-func NewCmdExec(cmdFullName string, f *cmdutil.Factory, cmdIn io.Reader, cmdOut, cmdErr io.Writer) *cobra.Command {
+func NewCmdExec(f *cmdutil.Factory, cmdIn io.Reader, cmdOut, cmdErr io.Writer) *cobra.Command {
 	options := &ExecOptions{
 		StreamOptions: StreamOptions{
 			In:  cmdIn,
@@ -60,8 +60,7 @@ func NewCmdExec(cmdFullName string, f *cmdutil.Factory, cmdIn io.Reader, cmdOut,
 			Err: cmdErr,
 		},
 
-		FullCmdName: cmdFullName,
-		Executor:    &DefaultRemoteExecutor{},
+		Executor: &DefaultRemoteExecutor{},
 	}
 	cmd := &cobra.Command{
 		Use:     "exec POD [-c CONTAINER] -- COMMAND [args...]",
@@ -131,18 +130,16 @@ type ExecOptions struct {
 
 	Command []string
 
-	FullCmdName string
-	Executor    RemoteExecutor
-	PodClient   coreclient.PodsGetter
-	Config      *restclient.Config
+	FullCmdName       string
+	SuggestedCmdUsage string
+
+	Executor  RemoteExecutor
+	PodClient coreclient.PodsGetter
+	Config    *restclient.Config
 }
 
 // Complete verifies command line arguments and loads data from the command environment
 func (p *ExecOptions) Complete(f *cmdutil.Factory, cmd *cobra.Command, argsIn []string, argsLenAtDash int) error {
-	if len(p.FullCmdName) == 0 {
-		p.FullCmdName = "kubectl"
-	}
-
 	// Let kubectl exec follow rules for `--`, see #13004 issue
 	if len(p.PodName) == 0 && (len(argsIn) == 0 || argsLenAtDash == 0) {
 		return cmdutil.UsageError(cmd, execUsageStr)
@@ -161,6 +158,14 @@ func (p *ExecOptions) Complete(f *cmdutil.Factory, cmd *cobra.Command, argsIn []
 		}
 	}
 
+	cmdParent := cmd.Parent()
+	if cmdParent != nil {
+		p.FullCmdName = cmdParent.CommandPath()
+	}
+	if len(p.FullCmdName) > 0 && cmdutil.IsSiblingCommandExists(cmd, "describe") {
+		p.SuggestedCmdUsage = fmt.Sprintf("Use '%s describe pod/%s' to see all of the containers in this pod.", p.FullCmdName, p.PodName)
+	}
+
 	namespace, _, err := f.DefaultNamespace()
 	if err != nil {
 		return err
@@ -265,7 +270,11 @@ func (p *ExecOptions) Run() error {
 	containerName := p.ContainerName
 	if len(containerName) == 0 {
 		if len(pod.Spec.Containers) > 1 {
-			fmt.Fprintf(p.Err, "defaulting container name to %s, use '%s describe pod/%s' to see all container names\n", pod.Spec.Containers[0].Name, p.FullCmdName, p.PodName)
+			usageString := fmt.Sprintf("Defaulting container name to %s.", pod.Spec.Containers[0].Name)
+			if len(p.SuggestedCmdUsage) > 0 {
+				usageString = fmt.Sprintf("%s\n%s", usageString, p.SuggestedCmdUsage)
+			}
+			fmt.Fprintf(p.Err, "%s\n", usageString)
 		}
 		containerName = pod.Spec.Containers[0].Name
 	}

pkg/kubectl/cmd/get.go

@@ -174,7 +174,7 @@ func RunGet(f *cmdutil.Factory, out io.Writer, errOut io.Writer, cmd *cobra.Comm
 
 		fullCmdName := cmd.Parent().CommandPath()
 		usageString := "Required resource not specified."
-		if len(fullCmdName) > 0 && cmdutil.IsCommandExists(cmd, "explain") {
+		if len(fullCmdName) > 0 && cmdutil.IsSiblingCommandExists(cmd, "explain") {
 			usageString = fmt.Sprintf("%s\nUse \"%s explain <resource>\" for a detailed description of that resource (e.g. %[2]s explain pods).", usageString, fullCmdName)
 		}
 

pkg/kubectl/cmd/util/helpers.go

@@ -716,3 +716,15 @@ func ObjectListToVersionedObject(objects []runtime.Object, version unversioned.G
 	}
 	return converted, nil
 }
+
+// IsSiblingCommandExists receives a pointer to a cobra command and a target string.
+// Returns true if the target string is found in the list of sibling commands.
+func IsSiblingCommandExists(cmd *cobra.Command, targetCmdName string) bool {
+	for _, c := range cmd.Parent().Commands() {
+		if c.Name() == targetCmdName {
+			return true
+		}
+	}
+
+	return false
+}