cmd/*: fail on unrecognized flags/arguments for component CLI

In case a malformed flag is passed to k8s components
such as "–foo", where "–" is not an ASCII dash character,
the components currently silently ignore the flag
and treat it as a positional argument.

Make k8s components/commands exit with an error if a positional argument
that is not empty is found. Include a custom error message for all
components except kubeadm, as cobra.NoArgs is used in a lot of
places already (can be fixed in a followup).

The kubelet already handles this properly - e.g.:
'unknown command: "–foo"'

This change affects:
- cloud-controller-manager
- kube-apiserver
- kube-controller-manager
- kube-proxy
- kubeadm {alpha|config|token|version}
- kubemark

Signed-off-by: Monis Khan <mok@vmware.com>
Signed-off-by: Lubomir I. Ivanov <lubomirivanov@vmware.com>

cmd/kube-scheduler/app/server.go

@@ -27,7 +27,7 @@ import (
 
 	"github.com/spf13/cobra"
 
-	"k8s.io/api/core/v1"
+	v1 "k8s.io/api/core/v1"
 	eventsv1beta1 "k8s.io/api/events/v1beta1"
 	utilerrors "k8s.io/apimachinery/pkg/util/errors"
 	"k8s.io/apiserver/pkg/authentication/authenticator"
@@ -83,11 +83,19 @@ kube-scheduler is the reference implementation.
 See [scheduling](https://kubernetes.io/docs/concepts/scheduling/)
 for more information about scheduling and the kube-scheduler component.`,
 		Run: func(cmd *cobra.Command, args []string) {
-			if err := runCommand(cmd, args, opts, registryOptions...); err != nil {
+			if err := runCommand(cmd, opts, registryOptions...); err != nil {
 				fmt.Fprintf(os.Stderr, "%v\n", err)
 				os.Exit(1)
 			}
 		},
+		Args: func(cmd *cobra.Command, args []string) error {
+			for _, arg := range args {
+				if len(arg) > 0 {
+					return fmt.Errorf("%q does not take any arguments, got %q", cmd.CommandPath(), args)
+				}
+			}
+			return nil
+		},
 	}
 	fs := cmd.Flags()
 	namedFlagSets := opts.Flags()
@@ -114,14 +122,14 @@ for more information about scheduling and the kube-scheduler component.`,
 }
 
 // runCommand runs the scheduler.
-func runCommand(cmd *cobra.Command, args []string, opts *options.Options, registryOptions ...Option) error {
+func runCommand(cmd *cobra.Command, opts *options.Options, registryOptions ...Option) error {
 	verflag.PrintAndExitIfRequested()
 	cliflag.PrintFlags(cmd.Flags())
 
 	ctx, cancel := context.WithCancel(context.Background())
 	defer cancel()
 
-	cc, sched, err := Setup(ctx, args, opts, registryOptions...)
+	cc, sched, err := Setup(ctx, opts, registryOptions...)
 	if err != nil {
 		return err
 	}
@@ -298,11 +306,7 @@ func WithPlugin(name string, factory framework.PluginFactory) Option {
 }
 
 // Setup creates a completed config and a scheduler based on the command args and options
-func Setup(ctx context.Context, args []string, opts *options.Options, outOfTreeRegistryOptions ...Option) (*schedulerserverconfig.CompletedConfig, *scheduler.Scheduler, error) {
-	if len(args) != 0 {
-		fmt.Fprint(os.Stderr, "arguments are not supported\n")
-	}
-
+func Setup(ctx context.Context, opts *options.Options, outOfTreeRegistryOptions ...Option) (*schedulerserverconfig.CompletedConfig, *scheduler.Scheduler, error) {
 	if errs := opts.Validate(); len(errs) > 0 {
 		return nil, nil, utilerrors.NewAggregate(errs)
 	}

cmd/kube-scheduler/app/server_test.go

@@ -373,10 +373,9 @@ profiles:
 				t.Fatal(err)
 			}
 
-			var args []string
 			ctx, cancel := context.WithCancel(context.Background())
 			defer cancel()
-			cc, sched, err := Setup(ctx, args, opts)
+			cc, sched, err := Setup(ctx, opts)
 			if err != nil {
 				t.Fatal(err)
 			}

cmd/kube-scheduler/app/testing/testserver.go

@@ -114,7 +114,7 @@ func StartTestServer(t Logger, customFlags []string) (result TestServer, err err
 		t.Logf("kube-scheduler will listen insecurely on port %d...", opts.CombinedInsecureServing.BindPort)
 	}
 
-	cc, sched, err := app.Setup(ctx, []string{}, opts)
+	cc, sched, err := app.Setup(ctx, opts)
 	if err != nil {
 		return result, fmt.Errorf("failed to create config from options: %v", err)
 	}