Add label filtering (-l) for get namespaces (#2915)

* Add label filtering (-l) for get namespaces

* Add ns as a shorthand

gwctl/cmd/describe.go

@@ -146,7 +146,7 @@ func runDescribe(cmd *cobra.Command, args []string, params *utils.CmdParams) {
 		}
 		backendsPrinter.PrintDescribeView(resourceModel)
 
-	case "namespace", "namespaces":
+	case "namespace", "namespaces", "ns":
 		filter := resourcediscovery.Filter{}
 		if len(args) > 1 {
 			filter.Name = args[1]

gwctl/cmd/get.go

@@ -87,8 +87,13 @@ func runGet(cmd *cobra.Command, args []string, params *utils.CmdParams) {
 	httpRoutesPrinter := &printer.HTTPRoutesPrinter{Out: params.Out, Clock: realClock}
 
 	switch kind {
-	case "namespace", "namespaces":
-		resourceModel, err := discoverer.DiscoverResourcesForNamespace(resourcediscovery.Filter{})
+	case "namespace", "namespaces", "ns":
+		selector, err := labels.Parse(labelSelector)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "Unable to find resources that match the label selector \"%s\": %v\n", labelSelector, err)
+			os.Exit(1)
+		}
+		resourceModel, err := discoverer.DiscoverResourcesForNamespace(resourcediscovery.Filter{Labels: selector})
 		if err != nil {
 			fmt.Fprintf(os.Stderr, "failed to discover Namespace resources: %v\n", err)
 			os.Exit(1)

gwctl/pkg/printer/namespace_test.go

@@ -27,6 +27,7 @@ import (
 	apiextensionsv1 "k8s.io/apiextensions-apiserver/pkg/apis/apiextensions/v1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
+	"k8s.io/apimachinery/pkg/labels"
 	"k8s.io/apimachinery/pkg/runtime"
 	testingclock "k8s.io/utils/clock/testing"
 
@@ -257,3 +258,58 @@ DirectlyAttachedPolicies:
 		t.Errorf("Unexpected diff\ngot=\n%v\nwant=\n%v\ndiff (-want +got)=\n%v", got, want, diff)
 	}
 }
+
+// TestNamespacesPrinter_LabelSelector tests label selector filtering for Namespaces in 'get' command.
+func TestNamespacesPrinter_LabelSelector(t *testing.T) {
+	fakeClock := testingclock.NewFakeClock(time.Now())
+	namespace := func(name string, labels map[string]string) *corev1.Namespace {
+		return &corev1.Namespace{
+			ObjectMeta: metav1.ObjectMeta{
+				Name: name,
+				CreationTimestamp: metav1.Time{
+					Time: fakeClock.Now().Add(-46 * 24 * time.Hour),
+				},
+				Labels: labels,
+			},
+			Status: corev1.NamespaceStatus{
+				Phase: corev1.NamespaceActive,
+			},
+		}
+	}
+
+	objects := []runtime.Object{
+		namespace("namespace-1", map[string]string{"app": "foo"}),
+		namespace("namespace-2", map[string]string{"app": "foo", "env": "internal"}),
+	}
+
+	params := utils.MustParamsForTest(t, common.MustClientsForTest(t, objects...))
+	discoverer := resourcediscovery.Discoverer{
+		K8sClients:    params.K8sClients,
+		PolicyManager: params.PolicyManager,
+	}
+	labelSelector := "env=internal"
+	selector, err := labels.Parse(labelSelector)
+	if err != nil {
+		t.Errorf("Unable to find resources that match the label selector \"%s\": %v\n", labelSelector, err)
+	}
+	resourceModel, err := discoverer.DiscoverResourcesForNamespace(resourcediscovery.Filter{Labels: selector})
+	if err != nil {
+		t.Fatalf("Failed to construct resourceModel: %v", resourceModel)
+	}
+
+	nsp := &NamespacesPrinter{
+		Out:   params.Out,
+		Clock: fakeClock,
+	}
+	nsp.Print(resourceModel)
+
+	got := params.Out.(*bytes.Buffer).String()
+	want := `
+NAME         STATUS  AGE
+namespace-2  Active  46d
+`
+
+	if diff := cmp.Diff(common.YamlString(want), common.YamlString(got), common.YamlStringTransformer); diff != "" {
+		t.Errorf("Unexpected diff\ngot=\n%v\nwant=\n%v\ndiff (-want +got)=\n%v", got, want, diff)
+	}
+}