check if namespace exists for task list command

pkg/cmd/task/list.go

@@ -76,6 +76,12 @@ func printTaskDetails(s *cli.Stream, p cli.Params) error {
 		return err
 	}
 
+	// Check if namespace exists. Return error if namespace specified with -n doesn't exist or if user doesn't have permissions to view.
+	_, err = cs.Kube.CoreV1().Namespaces().Get(p.Namespace(), metav1.GetOptions{})
+	if err != nil {
+		return err
+	}
+
 	tasks, err := listAllTasks(cs.Tekton, p.Namespace())
 	if err != nil {
 		fmt.Fprintf(os.Stderr, "Failed to list tasks from %s namespace \n", p.Namespace())

pkg/cmd/task/list_test.go

@@ -26,11 +26,36 @@ import (
 	"github.com/tektoncd/pipeline/pkg/apis/pipeline/v1alpha1"
 	pipelinetest "github.com/tektoncd/pipeline/test"
 	tb "github.com/tektoncd/pipeline/test/builder"
+	corev1 "k8s.io/api/core/v1"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 )
 
+func TestTaskList_Invalid_Namespace(t *testing.T) {
+	ns := []*corev1.Namespace{
+		{
+			ObjectMeta: metav1.ObjectMeta{
+				Name: "default",
+			},
+		},
+	}
+	cs, _ := test.SeedTestData(t, pipelinetest.Data{Namespaces: ns})
+	p := &test.Params{Tekton: cs.Pipeline, Kube: cs.Kube}
+
+	task := Command(p)
+	output, _ := test.ExecuteCommand(task, "list", "-n", "foo")
+	test.AssertOutput(t, "Error: namespaces \"foo\" not found\n", output)
+}
+
 func TestTaskList_Empty(t *testing.T) {
-	cs, _ := test.SeedTestData(t, pipelinetest.Data{})
-	p := &test.Params{Tekton: cs.Pipeline}
+	ns := []*corev1.Namespace{
+		{
+			ObjectMeta: metav1.ObjectMeta{
+				Name: "foo",
+			},
+		},
+	}
+	cs, _ := test.SeedTestData(t, pipelinetest.Data{Namespaces: ns})
+	p := &test.Params{Tekton: cs.Pipeline, Kube: cs.Kube}
 
 	task := Command(p)
 	output, err := test.ExecuteCommand(task, "list", "-n", "foo")
@@ -40,16 +65,25 @@ func TestTaskList_Empty(t *testing.T) {
 	test.AssertOutput(t, emptyMsg+"\n", output)
 }
 
-func TestTaskListOnlyTasks(t *testing.T) {
+func TestTaskList_Only_Tasks(t *testing.T) {
 	clock := clockwork.NewFakeClock()
+
 	tasks := []*v1alpha1.Task{
 		tb.Task("tomatoes", "namespace", cb.TaskCreationTime(clock.Now().Add(-1*time.Minute))),
 		tb.Task("mangoes", "namespace", cb.TaskCreationTime(clock.Now().Add(-20*time.Second))),
 		tb.Task("bananas", "namespace", cb.TaskCreationTime(clock.Now().Add(-512*time.Hour))),
 	}
 
-	cs, _ := test.SeedTestData(t, pipelinetest.Data{Tasks: tasks})
-	p := &test.Params{Tekton: cs.Pipeline, Clock: clock}
+	ns := []*corev1.Namespace{
+		{
+			ObjectMeta: metav1.ObjectMeta{
+				Name: "namespace",
+			},
+		},
+	}
+
+	cs, _ := test.SeedTestData(t, pipelinetest.Data{Tasks: tasks, Namespaces: ns})
+	p := &test.Params{Tekton: cs.Pipeline, Clock: clock, Kube: cs.Kube}
 
 	task := Command(p)
 	output, err := test.ExecuteCommand(task, "list", "-n", "namespace")

pkg/test/cobra.go

@@ -33,6 +33,7 @@ func ExecuteCommandC(c *cobra.Command, args ...string) (*cobra.Command, string,
 	buf := new(bytes.Buffer)
 	c.SetOutput(buf)
 	c.SetArgs(args)
+	c.SilenceUsage = true
 
 	root, err := c.ExecuteC()