Do some Kubectl optimizations suggested by the golangci linter

The tool golangci-lint gives a bunch of warnings. This PR solves the easier/less controversial ones, so the code is simpler and a little bit more optimal, since it removes some if conditions.

staging/src/k8s.io/kubectl/pkg/cmd/create/create_role_test.go

@@ -140,7 +140,7 @@ func TestCreateRole(t *testing.T) {
 			cmd.Run(cmd, []string{roleName})
 			actual := &rbac.Role{}
 			if err := runtime.DecodeInto(scheme.Codecs.UniversalDecoder(), buf.Bytes(), actual); err != nil {
-				t.Log(string(buf.Bytes()))
+				t.Log(buf.String())
 				t.Fatal(err)
 			}
 			if !equality.Semantic.DeepEqual(test.expectedRole, actual) {

staging/src/k8s.io/kubectl/pkg/cmd/delete/delete_test.go

@@ -706,7 +706,7 @@ func TestResourceErrors(t *testing.T) {
 			}
 
 			if buf.Len() > 0 {
-				t.Errorf("buffer should be empty: %s", string(buf.Bytes()))
+				t.Errorf("buffer should be empty: %s", buf.String())
 			}
 		})
 	}

staging/src/k8s.io/kubectl/pkg/cmd/describe/describe_test.go

@@ -59,7 +59,7 @@ func TestDescribeUnknownSchemaObject(t *testing.T) {
 		t.Errorf("unexpected describer: %#v", d)
 	}
 
-	if buf.String() != fmt.Sprintf("%s", d.Output) {
+	if buf.String() != d.Output {
 		t.Errorf("unexpected output: %s", buf.String())
 	}
 }
@@ -92,7 +92,7 @@ func TestDescribeUnknownNamespacedSchemaObject(t *testing.T) {
 		t.Errorf("unexpected describer: %#v", d)
 	}
 
-	if buf.String() != fmt.Sprintf("%s", d.Output) {
+	if buf.String() != d.Output {
 		t.Errorf("unexpected output: %s", buf.String())
 	}
 }
@@ -133,7 +133,7 @@ func TestDescribeObject(t *testing.T) {
 		t.Errorf("unexpected describer: %#v", d)
 	}
 
-	if buf.String() != fmt.Sprintf("%s", d.Output) {
+	if buf.String() != d.Output {
 		t.Errorf("unexpected output: %s", buf.String())
 	}
 }

staging/src/k8s.io/kubectl/pkg/cmd/plugin/plugin.go

@@ -99,7 +99,7 @@ func NewCmdPluginList(f cmdutil.Factory, streams genericclioptions.IOStreams) *c
 func (o *PluginListOptions) Complete(cmd *cobra.Command) error {
 	o.Verifier = &CommandOverrideVerifier{
 		root:        cmd.Root(),
-		seenPlugins: make(map[string]string, 0),
+		seenPlugins: make(map[string]string),
 	}
 
 	o.PluginPaths = filepath.SplitList(os.Getenv("PATH"))

staging/src/k8s.io/kubectl/pkg/cmd/set/env/env_parse.go

@@ -81,7 +81,7 @@ func parseIntoEnvVar(spec []string, defaultReader io.Reader, envVarType string)
 				return nil, nil, err
 			}
 			env = append(env, fileEnv...)
-		case strings.Index(envSpec, "=") != -1:
+		case strings.Contains(envSpec, "="):
 			parts := strings.SplitN(envSpec, "=", 2)
 			if len(parts) != 2 {
 				return nil, nil, fmt.Errorf("invalid %s: %v", envVarType, envSpec)
@@ -119,7 +119,8 @@ func readEnv(r io.Reader, envVarType string) ([]v1.EnvVar, error) {
 		if pos := strings.Index(envSpec, "#"); pos != -1 {
 			envSpec = envSpec[:pos]
 		}
-		if strings.Index(envSpec, "=") != -1 {
+
+		if strings.Contains(envSpec, "=") {
 			parts := strings.SplitN(envSpec, "=", 2)
 			if len(parts) != 2 {
 				return nil, fmt.Errorf("invalid %s: %v", envVarType, envSpec)
@@ -130,8 +131,10 @@ func readEnv(r io.Reader, envVarType string) ([]v1.EnvVar, error) {
 			})
 		}
 	}
+
 	if err := scanner.Err(); err != nil && err != io.EOF {
 		return nil, err
 	}
+
 	return env, nil
 }

staging/src/k8s.io/kubectl/pkg/cmd/util/sanity/cmd_sanity.go

@@ -80,7 +80,7 @@ func RunCmdChecks(cmd *cobra.Command, cmdChecks []CmdCheck, skipCmd []string) []
 	fmt.Fprintf(os.Stdout, "---+ RUNNING COMMAND CHECKS on %q\n", cmdPath)
 
 	for _, check := range cmdChecks {
-		if err := check(cmd); err != nil && len(err) > 0 {
+		if err := check(cmd); len(err) > 0 {
 			errors = append(errors, err...)
 		}
 	}

staging/src/k8s.io/kubectl/pkg/describe/versioned/describe.go

@@ -777,10 +777,11 @@ func describePodIPs(pod *corev1.Pod, w PrefixWriter, space string) {
 }
 
 func describeVolumes(volumes []corev1.Volume, w PrefixWriter, space string) {
-	if volumes == nil || len(volumes) == 0 {
+	if len(volumes) == 0 {
 		w.Write(LEVEL_0, "%sVolumes:\t<none>\n", space)
 		return
 	}
+
 	w.Write(LEVEL_0, "%sVolumes:\n", space)
 	for _, volume := range volumes {
 		nameIndent := ""
@@ -2426,7 +2427,6 @@ func describeIngressTLS(w PrefixWriter, ingTLS []networkingv1beta1.IngressTLS) {
 			w.Write(LEVEL_1, "%v terminates %v\n", t.SecretName, strings.Join(t.Hosts, ","))
 		}
 	}
-	return
 }
 
 // TODO: Move from annotations into Ingress status.
@@ -2435,7 +2435,6 @@ func describeIngressAnnotations(w PrefixWriter, annotations map[string]string) {
 	for k, v := range annotations {
 		w.Write(LEVEL_1, "%v:\t%s\n", k, v)
 	}
-	return
 }
 
 // ServiceDescriber generates information about a service.
@@ -2742,8 +2741,8 @@ func (d *ServiceAccountDescriber) Describe(namespace, name string, describerSett
 
 		for _, s := range secrets.Items {
 			if s.Type == corev1.SecretTypeServiceAccountToken {
-				name, _ := s.Annotations[corev1.ServiceAccountNameKey]
-				uid, _ := s.Annotations[corev1.ServiceAccountUIDKey]
+				name := s.Annotations[corev1.ServiceAccountNameKey]
+				uid := s.Annotations[corev1.ServiceAccountUIDKey]
 				if name == serviceAccount.Name && uid == string(serviceAccount.UID) {
 					tokens = append(tokens, s)
 				}
@@ -4319,7 +4318,7 @@ func printLabelsMultiline(w PrefixWriter, title string, labels map[string]string
 func printLabelsMultilineWithIndent(w PrefixWriter, initialIndent, title, innerIndent string, labels map[string]string, skip sets.String) {
 	w.Write(LEVEL_0, "%s%s:%s", initialIndent, title, innerIndent)
 
-	if labels == nil || len(labels) == 0 {
+	if len(labels) == 0 {
 		w.WriteLine("<none>")
 		return
 	}
@@ -4357,7 +4356,7 @@ func printNodeTaintsMultiline(w PrefixWriter, title string, taints []corev1.Tain
 func printTaintsMultilineWithIndent(w PrefixWriter, initialIndent, title, innerIndent string, taints []corev1.Taint) {
 	w.Write(LEVEL_0, "%s%s:%s", initialIndent, title, innerIndent)
 
-	if taints == nil || len(taints) == 0 {
+	if len(taints) == 0 {
 		w.WriteLine("<none>")
 		return
 	}
@@ -4388,7 +4387,7 @@ func printPodsMultiline(w PrefixWriter, title string, pods []corev1.Pod) {
 func printPodsMultilineWithIndent(w PrefixWriter, initialIndent, title, innerIndent string, pods []corev1.Pod) {
 	w.Write(LEVEL_0, "%s%s:%s", initialIndent, title, innerIndent)
 
-	if pods == nil || len(pods) == 0 {
+	if len(pods) == 0 {
 		w.WriteLine("<none>")
 		return
 	}
@@ -4419,7 +4418,7 @@ func printPodTolerationsMultiline(w PrefixWriter, title string, tolerations []co
 func printTolerationsMultilineWithIndent(w PrefixWriter, initialIndent, title, innerIndent string, tolerations []corev1.Toleration) {
 	w.Write(LEVEL_0, "%s%s:%s", initialIndent, title, innerIndent)
 
-	if tolerations == nil || len(tolerations) == 0 {
+	if len(tolerations) == 0 {
 		w.WriteLine("<none>")
 		return
 	}

staging/src/k8s.io/kubectl/pkg/drain/cordon.go

@@ -62,10 +62,8 @@ func NewCordonHelperFromRuntimeObject(nodeObject runtime.Object, scheme *runtime
 // or false when no change is needed
 func (c *CordonHelper) UpdateIfRequired(desired bool) bool {
 	c.desired = desired
-	if c.node.Spec.Unschedulable == c.desired {
-		return false
-	}
-	return true
+
+	return c.node.Spec.Unschedulable != c.desired
 }
 
 // PatchOrReplace uses given clientset to update the node status, either by patching or

staging/src/k8s.io/kubectl/pkg/util/i18n/i18n.go

@@ -76,11 +76,9 @@ func findLanguage(root string, getLanguageFn func() string) string {
 	langStr := getLanguageFn()
 
 	translations := knownTranslations[root]
-	if translations != nil {
-		for ix := range translations {
-			if translations[ix] == langStr {
-				return langStr
-			}
+	for ix := range translations {
+		if translations[ix] == langStr {
+			return langStr
 		}
 	}
 	klog.V(3).Infof("Couldn't find translations for %s, using default", langStr)