Auto-select EventListener in describe if only one is present

- When only one EventListener is present on the cluster then it should
be auto-selected when executing the `eventlistener describe` command.

- When there are more than one EventListener then user will get an
interactive option to select and describe it.

- Created a package `pkg/eventlistener/eventlistener.go` which contains
the helper functions for EventListener and also added the tests for
same.

- Moved the `list` function from `pkg/cmd/eventlistener/list.go` to
`pkg/eventlistener/eventlistener.go`.

Signed-off-by: vinamra28 <vinjain@redhat.com>

Author: vinamra28

pkg/cmd/eventlistener/describe.go

@@ -25,7 +25,9 @@ import (
 
 	"github.com/spf13/cobra"
 	"github.com/tektoncd/cli/pkg/cli"
+	"github.com/tektoncd/cli/pkg/eventlistener"
 	"github.com/tektoncd/cli/pkg/formatted"
+	"github.com/tektoncd/cli/pkg/options"
 	"github.com/tektoncd/cli/pkg/printer"
 	"github.com/tektoncd/triggers/pkg/apis/triggers/v1alpha1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
@@ -129,6 +131,7 @@ const describeTemplate = `{{decorate "bold" "Name"}}:	{{ .EventListener.Name }}
 
 func describeCommand(p cli.Params) *cobra.Command {
 	f := cliopts.NewPrintFlags("describe")
+	opts := &options.DescribeOptions{Params: p}
 	eg := `Describe an EventListener of name 'foo' in namespace 'bar':
 
     tkn eventlistener describe foo -n bar
@@ -146,7 +149,6 @@ or
 		Annotations: map[string]string{
 			"commandType": "main",
 		},
-		Args:              cobra.MinimumNArgs(1),
 		SilenceUsage:      true,
 		ValidArgsFunction: formatted.ParentCompletion,
 		RunE: func(cmd *cobra.Command, args []string) error {
@@ -155,19 +157,41 @@ or
 				Err: cmd.OutOrStderr(),
 			}
 
+			cs, err := p.Clients()
+			if err != nil {
+				return err
+			}
+
 			output, err := cmd.LocalFlags().GetString("output")
 			if err != nil {
 				fmt.Fprint(os.Stderr, "Error: output option not set properly \n")
 				return err
 			}
 
+			if len(args) == 0 {
+				eventListenerNames, err := eventlistener.GetAllEventListenerNames(cs.Triggers, p.Namespace())
+				if err != nil {
+					return err
+				}
+				if len(eventListenerNames) == 1 {
+					opts.EventListenerName = eventListenerNames[0]
+				} else {
+					err = askEventListenerName(opts, eventListenerNames)
+					if err != nil {
+						return err
+					}
+				}
+			} else {
+				opts.EventListenerName = args[0]
+			}
+
 			if output != "" {
 				if strings.ToLower(output) == "url" {
 					return describeEventListenerOutputURL(cmd.OutOrStdout(), p, args[0])
 				}
 				return describeEventListenerOutput(cmd.OutOrStdout(), p, f, args[0])
 			}
-			return printEventListenerDescription(s, p, args[0])
+			return printEventListenerDescription(s, p, opts.EventListenerName)
 		},
 	}
 
@@ -296,3 +320,15 @@ func isBindingNameExist(bindings []*v1alpha1.EventListenerBinding) bool {
 func isTemplateRefExist(templates *v1alpha1.EventListenerTemplate) bool {
 	return templates.Ref != nil
 }
+
+func askEventListenerName(opts *options.DescribeOptions, eventListenerNames []string) error {
+	if len(eventListenerNames) == 0 {
+		return fmt.Errorf("no EventListeners found")
+	}
+	err := opts.Ask(options.ResourceNameEventListener, eventListenerNames)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}

pkg/cmd/eventlistener/describe_test.go

@@ -430,6 +430,42 @@ func TestEventListenerDescribe_OutputStatusURL_WithNoURL(t *testing.T) {
 	test.AssertOutput(t, "Error: "+err.Error()+"\n", out)
 }
 
+func TestEventListenerDescribe_AutoSelect(t *testing.T) {
+	triggerTemplateRef := "tt1"
+	els := []*v1alpha1.EventListener{
+		{
+			ObjectMeta: metav1.ObjectMeta{
+				Name:      "el1",
+				Namespace: "ns",
+			},
+			Spec: v1alpha1.EventListenerSpec{
+				Triggers: []v1alpha1.EventListenerTrigger{
+					{
+						Template: &v1alpha1.TriggerSpecTemplate{
+							Ref:        &triggerTemplateRef,
+							APIVersion: "v1alpha1",
+						},
+					},
+				},
+			},
+		},
+	}
+
+	cs := test.SeedTestResources(t, triggertest.Resources{EventListeners: els, Namespaces: []*corev1.Namespace{{
+		ObjectMeta: metav1.ObjectMeta{
+			Name: "ns",
+		},
+	}}})
+	p := &test.Params{Triggers: cs.Triggers, Kube: cs.Kube}
+
+	eventListener := Command(p)
+	out, err := test.ExecuteCommand(eventListener, "desc", "-n", "ns")
+	if err != nil {
+		t.Errorf("Error expected here")
+	}
+	golden.Assert(t, out, fmt.Sprintf("%s.golden", t.Name()))
+}
+
 func executeEventListenerCommand(t *testing.T, els []*v1alpha1.EventListener) {
 	cs := test.SeedTestResources(t, triggertest.Resources{EventListeners: els, Namespaces: []*corev1.Namespace{{
 		ObjectMeta: metav1.ObjectMeta{

pkg/cmd/eventlistener/list.go

@@ -15,20 +15,17 @@
 package eventlistener
 
 import (
-	"context"
 	"errors"
 	"fmt"
 	"text/tabwriter"
 
 	"github.com/spf13/cobra"
 	"github.com/tektoncd/cli/pkg/cli"
+	"github.com/tektoncd/cli/pkg/eventlistener"
 	"github.com/tektoncd/cli/pkg/formatted"
 	"github.com/tektoncd/cli/pkg/printer"
 	"github.com/tektoncd/triggers/pkg/apis/triggers/v1alpha1"
-	"github.com/tektoncd/triggers/pkg/client/clientset/versioned"
 	corev1 "k8s.io/api/core/v1"
-	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
-	"k8s.io/apimachinery/pkg/runtime/schema"
 	cliopts "k8s.io/cli-runtime/pkg/genericclioptions"
 )
 
@@ -73,7 +70,7 @@ or
 				namespace = ""
 			}
 
-			els, err := list(cs.Triggers, namespace)
+			els, err := eventlistener.List(cs.Triggers, namespace)
 			if err != nil {
 				if opts.AllNamespaces {
 					return fmt.Errorf("failed to list EventListeners from all namespaces: %v", err)
@@ -108,23 +105,6 @@ or
 	return c
 }
 
-func list(client versioned.Interface, namespace string) (*v1alpha1.EventListenerList, error) {
-	els, err := client.TriggersV1alpha1().EventListeners(namespace).List(context.Background(), metav1.ListOptions{})
-	if err != nil {
-		return nil, err
-	}
-
-	// NOTE: this is required for -o json|yaml to work properly since
-	// tektoncd go client fails to set these; probably a bug
-	els.GetObjectKind().SetGroupVersionKind(
-		schema.GroupVersionKind{
-			Version: "triggers.tekton.dev/v1alpha1",
-			Kind:    "EventListenerList",
-		})
-
-	return els, nil
-}
-
 func printFormatted(s *cli.Stream, els *v1alpha1.EventListenerList, p cli.Params, allNamespaces bool, noHeaders bool) error {
 	if len(els.Items) == 0 {
 		fmt.Fprintln(s.Err, emptyMsg)

pkg/cmd/eventlistener/testdata/TestEventListenerDescribe_AutoSelect.golden

@@ -0,0 +1,8 @@
+Name:        el1
+Namespace:   ns
+
+EventListenerTriggers
+
+ TEMPLATE REF   APIVERSION
+ tt1            v1alpha1
+ 

pkg/cmd/eventlistener/testdata/TestEventListenerDescribe_NoArgProvided.golden

@@ -1 +1 @@
-Error: requires at least 1 arg(s), only received 0
+Error: no EventListeners found

pkg/eventlistener/eventlistener.go

@@ -0,0 +1,55 @@
+// Copyright © 2021 The Tekton Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package eventlistener
+
+import (
+	"context"
+
+	"github.com/tektoncd/triggers/pkg/apis/triggers/v1alpha1"
+	"github.com/tektoncd/triggers/pkg/client/clientset/versioned"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/runtime/schema"
+)
+
+func GetAllEventListenerNames(client versioned.Interface, namespace string) ([]string, error) {
+
+	ps, err := List(client, namespace)
+	if err != nil {
+		return nil, err
+	}
+
+	ret := []string{}
+	for _, item := range ps.Items {
+		ret = append(ret, item.ObjectMeta.Name)
+	}
+	return ret, nil
+}
+
+func List(client versioned.Interface, namespace string) (*v1alpha1.EventListenerList, error) {
+	els, err := client.TriggersV1alpha1().EventListeners(namespace).List(context.Background(), metav1.ListOptions{})
+	if err != nil {
+		return nil, err
+	}
+
+	// NOTE: this is required for -o json|yaml to work properly since
+	// tektoncd go client fails to set these; probably a bug
+	els.GetObjectKind().SetGroupVersionKind(
+		schema.GroupVersionKind{
+			Version: "triggers.tekton.dev/v1alpha1",
+			Kind:    "EventListenerList",
+		})
+
+	return els, nil
+}