Merge pull request #32722 from juanvallejo/jvallejo_return-err-on-oc-get-empty-list

Automatic merge from submit-queue

return warning on empty list result in kubectl get

**Release note**:
```release-note
NONE
```

The current default behavior of `kubectl get` is to return an empty
output when there are no resources to display. This patch improves
usability by returning a warning through stderr in the case of an empty
list.

##### Before
`$ kubectl get pods`
  - *empty output*

##### After
`$ kubectl get pods`
```
There are no resources to display.
```

pkg/kubectl/cmd/get.go

@@ -125,7 +125,7 @@ func NewCmdGet(f *cmdutil.Factory, out io.Writer, errOut io.Writer) *cobra.Comma
 
 // RunGet implements the generic Get command
 // TODO: convert all direct flag accessors to a struct and pass that instead of cmd
-func RunGet(f *cmdutil.Factory, out io.Writer, errOut io.Writer, cmd *cobra.Command, args []string, options *GetOptions) error {
+func RunGet(f *cmdutil.Factory, out, errOut io.Writer, cmd *cobra.Command, args []string, options *GetOptions) error {
 	if len(options.Raw) > 0 {
 		restClient, err := f.RESTClient()
 		if err != nil {
@@ -322,6 +322,9 @@ func RunGet(f *cmdutil.Factory, out io.Writer, errOut io.Writer, cmd *cobra.Comm
 			}
 			errs = append(errs, err)
 		}
+		if len(infos) == 0 {
+			outputEmptyListWarning(errOut)
+		}
 
 		res := ""
 		if len(infos) > 0 {
@@ -371,6 +374,9 @@ func RunGet(f *cmdutil.Factory, out io.Writer, errOut io.Writer, cmd *cobra.Comm
 	if err != nil {
 		allErrs = append(allErrs, err)
 	}
+	if len(infos) == 0 {
+		outputEmptyListWarning(errOut)
+	}
 
 	objs := make([]runtime.Object, len(infos))
 	for ix := range infos {
@@ -492,3 +498,9 @@ func RunGet(f *cmdutil.Factory, out io.Writer, errOut io.Writer, cmd *cobra.Comm
 	}
 	return utilerrors.NewAggregate(allErrs)
 }
+
+// outputEmptyListWarning outputs a warning indicating that no items are available to display
+func outputEmptyListWarning(out io.Writer) error {
+	_, err := fmt.Fprintf(out, "%s\n", "No resources found.")
+	return err
+}