Add support for service url in svc describe output (#916)

* Add support for service url in svc describe output

* Add changes in CHANGELOG.adoc

* Update CHANGELOG.adoc

Co-authored-by: Matt Moore <mattmoor@vmware.com>

* Add url as output format in kn service describe --help command

* Build locally and autogenerated doc

* Change service describe help message for consistency

Co-authored-by: Matt Moore <mattmoor@vmware.com>

CHANGELOG.adoc

@@ -18,6 +18,10 @@
 |===
 | | Description | PR
 
+| 🎁
+| Add "url" output format to return service url in service describe
+| https://github.com/knative/client/pull/916[#916]
+
 | 🐛
 | Fix panic for `kn source apiserver` and `kn source binding` describe with Sink URI
 | https://github.com/knative/client/pull/901[#901]

docs/cmd/kn_service_describe.md

@@ -10,13 +10,27 @@ Show details of a service
 kn service describe NAME
 ```
 
+### Examples
+
+```
+
+  # Describe service 'svc' in human friendly format
+  kn service describe svc
+
+  # Describe service 'svc' in YAML format
+  kn service describe svc -o yaml
+
+  # Print only service URL
+  kn service describe svc -o url
+```
+
 ### Options
 
 ```
       --allow-missing-template-keys   If true, ignore any errors in templates when a field or map key is missing in the template. Only applies to golang and jsonpath output formats. (default true)
   -h, --help                          help for describe
   -n, --namespace string              Specify the namespace to operate in.
-  -o, --output string                 Output format. One of: json|yaml|name|go-template|go-template-file|template|templatefile|jsonpath|jsonpath-file.
+  -o, --output string                 Output format. One of: json|yaml|name|go-template|go-template-file|template|templatefile|jsonpath|jsonpath-file|url.
       --template string               Template string or path to template file to use when -o=go-template, -o=go-template-file. The template format is golang templates [http://golang.org/pkg/text/template/#pkg-overview].
   -v, --verbose                       More output.
 ```

pkg/kn/commands/service/describe.go

@@ -20,6 +20,7 @@ import (
 	"io"
 	"sort"
 	"strconv"
+	"strings"
 
 	"k8s.io/apimachinery/pkg/util/sets"
 	"k8s.io/cli-runtime/pkg/genericclioptions"
@@ -70,6 +71,16 @@ type revisionDesc struct {
 // As this command does not do any writes/updates, it's just a matter of fallbacks.
 // [/REMOVE COMMENT WHEN MOVING TO 0.7.0]
 
+var describe_example = `
+  # Describe service 'svc' in human friendly format
+  kn service describe svc
+
+  # Describe service 'svc' in YAML format
+  kn service describe svc -o yaml
+
+  # Print only service URL
+  kn service describe svc -o url`
+
 // NewServiceDescribeCommand returns a new command for describing a service.
 func NewServiceDescribeCommand(p *commands.KnParams) *cobra.Command {
 
@@ -77,8 +88,9 @@ func NewServiceDescribeCommand(p *commands.KnParams) *cobra.Command {
 	machineReadablePrintFlags := genericclioptions.NewPrintFlags("")
 
 	command := &cobra.Command{
-		Use:   "describe NAME",
+		Use:     "describe NAME",
-		Short: "Show details of a service",
+		Short:   "Show details of a service",
+		Example: describe_example,
 		RunE: func(cmd *cobra.Command, args []string) error {
 			if len(args) != 1 {
 				return errors.New("'service describe' requires the service name given as single argument")
@@ -102,11 +114,16 @@ func NewServiceDescribeCommand(p *commands.KnParams) *cobra.Command {
 
 			// Print out machine readable output if requested
 			if machineReadablePrintFlags.OutputFlagSpecified() {
+				out := cmd.OutOrStdout()
+				if strings.ToLower(*machineReadablePrintFlags.OutputFormat) == "url" {
+					fmt.Fprintf(out, "%s\n", extractURL(service))
+					return nil
+				}
 				printer, err := machineReadablePrintFlags.ToPrinter()
 				if err != nil {
 					return err
 				}
-				return printer.PrintObj(service, cmd.OutOrStdout())
+				return printer.PrintObj(service, out)
 			}
 
 			printDetails, err = cmd.Flags().GetBool("verbose")
@@ -126,6 +143,7 @@ func NewServiceDescribeCommand(p *commands.KnParams) *cobra.Command {
 	commands.AddNamespaceFlags(flags, false)
 	flags.BoolP("verbose", "v", false, "More output.")
 	machineReadablePrintFlags.AddFlags(command)
+	command.Flag("output").Usage = fmt.Sprintf("Output format. One of: %s.", strings.Join(append(machineReadablePrintFlags.AllowedFormats(), "url"), "|"))
 	return command
 }
 

pkg/kn/commands/service/describe_test.go

@@ -506,6 +506,23 @@ func TestServiceDescribeMachineReadable(t *testing.T) {
 	r.Validate()
 }
 
+func TestServiceDescribeURL(t *testing.T) {
+	client := knclient.NewMockKnServiceClient(t)
+
+	// Recording:
+	r := client.Recorder()
+
+	// Prepare service
+	expectedService := createTestService("foo", []string{"rev1", "rev2"}, goodConditions())
+	r.GetService("foo", &expectedService, nil)
+
+	output, err := executeServiceCommand(client, "describe", "foo", "-o", "url")
+	assert.NilError(t, err)
+	assert.Assert(t, util.ContainsAll(output, "foo.default.example.com"))
+
+	r.Validate()
+}
+
 func validateServiceOutput(t *testing.T, service string, output string) {
 	assert.Assert(t, cmp.Regexp("Name:\\s+"+service, output))
 	assert.Assert(t, cmp.Regexp("Namespace:\\s+default", output))