kubectl version should print just client information in the absence of kubeconfig

pkg/kubectl/cmd/version/BUILD

@@ -13,6 +13,7 @@ go_library(
         "//staging/src/k8s.io/apimachinery/pkg/version:go_default_library",
         "//staging/src/k8s.io/cli-runtime/pkg/genericclioptions:go_default_library",
         "//staging/src/k8s.io/client-go/discovery:go_default_library",
+        "//staging/src/k8s.io/client-go/tools/clientcmd:go_default_library",
         "//vendor/github.com/ghodss/yaml:go_default_library",
         "//vendor/github.com/spf13/cobra:go_default_library",
     ],

pkg/kubectl/cmd/version/version.go

@@ -27,6 +27,7 @@ import (
 	apimachineryversion "k8s.io/apimachinery/pkg/version"
 	"k8s.io/cli-runtime/pkg/genericclioptions"
 	"k8s.io/client-go/discovery"
+	"k8s.io/client-go/tools/clientcmd"
 	cmdutil "k8s.io/kubernetes/pkg/kubectl/cmd/util"
 	"k8s.io/kubernetes/pkg/kubectl/util/i18n"
 	"k8s.io/kubernetes/pkg/kubectl/util/templates"
@@ -83,7 +84,9 @@ func NewCmdVersion(f cmdutil.Factory, ioStreams genericclioptions.IOStreams) *co
 func (o *VersionOptions) Complete(f cmdutil.Factory, cmd *cobra.Command) error {
 	var err error
 	o.discoveryClient, err = f.ToDiscoveryClient()
-	if err != nil {
+	// if we had an empty rest.Config, continue and just print out client information.
+	// if we had an error other than being unable to build a rest.Config, fail.
+	if err != nil && !clientcmd.IsEmptyConfig(err) {
 		return err
 	}
 	return nil
@@ -107,7 +110,7 @@ func (o *VersionOptions) Run() error {
 	clientVersion := version.Get()
 	versionInfo.ClientVersion = &clientVersion
 
-	if !o.ClientOnly {
+	if !o.ClientOnly && o.discoveryClient != nil {
 		// Always request fresh data from the server
 		o.discoveryClient.Invalidate()
 		serverVersion, serverErr = o.discoveryClient.ServerVersion()