Adds more columns in service list command output

 This commit adds basic details about service in
 service list command output.
 text/tabwriter is used to print columns on stdout.

 Fixes #knative#40

pkg/kn/commands/service_list.go

@@ -15,6 +15,12 @@
 package commands
 
 import (
+	"fmt"
+	"strings"
+	"text/tabwriter"
+
+	printers "github.com/knative/client/pkg/util/printers"
+	servingv1alpha1 "github.com/knative/serving/pkg/apis/serving/v1alpha1"
 	"github.com/spf13/cobra"
 	v1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/runtime/schema"
@@ -23,11 +29,8 @@ import (
 
 var serviceListPrintFlags *genericclioptions.PrintFlags
 
-// listCmd represents the list command
+// NewServiceListCommand represents the list command
 func NewServiceListCommand(p *KnParams) *cobra.Command {
-
-	serviceListPrintFlags := genericclioptions.NewPrintFlags("").WithDefaultOutput(
-		"jsonpath={range .items[*]}{.metadata.name}{\"\\n\"}{end}")
 	serviceListCommand := &cobra.Command{
 		Use:   "list",
 		Short: "List available services.",
@@ -42,21 +45,40 @@ func NewServiceListCommand(p *KnParams) *cobra.Command {
 				return err
 			}
 
-			printer, err := serviceListPrintFlags.ToPrinter()
-			if err != nil {
-				return err
-			}
 			service.GetObjectKind().SetGroupVersionKind(schema.GroupVersionKind{
 				Group:   "knative.dev",
 				Version: "v1alpha1",
 				Kind:    "Service"})
-			err = printer.PrintObj(service, cmd.OutOrStdout())
-			if err != nil {
+
+			printer := printers.GetNewTabWriter(cmd.OutOrStdout())
+
+			if err := printServiceList(printer, *service); err != nil {
 				return err
 			}
-			return nil
+			printer.Flush()
+
+			return err
 		},
 	}
-	serviceListPrintFlags.AddFlags(serviceListCommand)
 	return serviceListCommand
 }
+
+func printServiceList(printer *tabwriter.Writer, services servingv1alpha1.ServiceList) error {
+	// case where no services are present
+	if len(services.Items) < 1 {
+		fmt.Fprintln(printer, "No resources found.")
+		return nil
+	}
+	columnNames := []string{"NAME", "DOMAIN", "LATESTCREATED", "LATESTREADY"}
+	if _, err := fmt.Fprintf(printer, "%s\n", strings.Join(columnNames, "\t")); err != nil {
+		return err
+	}
+	for _, ksvc := range services.Items {
+		_, err := fmt.Fprintf(printer, "%s\n", strings.Join([]string{ksvc.Name, ksvc.Status.Domain,
+			ksvc.Status.LatestCreatedRevisionName, ksvc.Status.LatestReadyRevisionName}, "\t"))
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}

pkg/util/printers/tabwriter.go

@@ -0,0 +1,34 @@
+// Copyright © 2018 The Knative 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 implie
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package printers
+
+import (
+	"io"
+
+	"text/tabwriter"
+)
+
+const (
+	tabwriterMinWidth = 6
+	tabwriterWidth    = 4
+	tabwriterPadding  = 3
+	tabwriterPadChar  = ' '
+	tabwriterFlags    = tabwriter.TabIndent
+)
+
+// GetNewTabWriter returns a tabwriter that translates tabbed columns in input into properly aligned text.
+func GetNewTabWriter(output io.Writer) *tabwriter.Writer {
+	return tabwriter.NewWriter(output, tabwriterMinWidth, tabwriterWidth, tabwriterPadding, tabwriterPadChar, tabwriterFlags)
+}