fix error when output is set to name

pkg/kn/commands/service/list.go

@@ -24,6 +24,7 @@ import (
 	"knative.dev/client/pkg/kn/commands"
 	"knative.dev/client/pkg/kn/commands/flags"
 	clientservingv1 "knative.dev/client/pkg/serving/v1"
+	"knative.dev/client/pkg/util"
 )
 
 // NewServiceListCommand represents 'kn service list' command
@@ -81,11 +82,15 @@ func NewServiceListCommand(p *commands.KnParams) *cobra.Command {
 				return a.ObjectMeta.Name < b.ObjectMeta.Name
 			})
 
-			err = printer.PrintObj(serviceList, cmd.OutOrStdout())
-			if err != nil {
-				return err
+			if serviceListFlags.GenericPrintFlags.OutputFlagSpecified() {
+				unstructedList, err := util.ToUnstructuredList(serviceList)
+				if err != nil {
+					return err
+				}
+				return printer.PrintObj(unstructedList, cmd.OutOrStdout())
 			}
-			return nil
+
+			return printer.PrintObj(serviceList, cmd.OutOrStdout())
 		},
 	}
 	commands.AddNamespaceFlags(serviceListCommand.Flags(), true)

pkg/util/unstructured.go

@@ -0,0 +1,58 @@
+// Copyright © 2020 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 implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package util
+
+import (
+	"encoding/json"
+
+	"k8s.io/apimachinery/pkg/api/meta"
+	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
+	"k8s.io/apimachinery/pkg/runtime"
+)
+
+func ToUnstructuredList(obj runtime.Object) (*unstructured.UnstructuredList, error) {
+	unstructuredList := &unstructured.UnstructuredList{}
+	unstructuredList.SetGroupVersionKind(obj.GetObjectKind().GroupVersionKind())
+	if meta.IsListType(obj) {
+		items, err := meta.ExtractList(obj)
+		if err != nil {
+			return nil, err
+		}
+		for _, obj := range items {
+			ud, err := toUnstructured(obj)
+			if err != nil {
+				return nil, err
+			}
+			unstructuredList.Items = append(unstructuredList.Items, *ud)
+		}
+
+	} else {
+
+	}
+	return unstructuredList, nil
+
+}
+
+func toUnstructured(obj runtime.Object) (*unstructured.Unstructured, error) {
+	b, err := json.Marshal(obj)
+	if err != nil {
+		return nil, err
+	}
+	ud := &unstructured.Unstructured{}
+	if err := json.Unmarshal(b, ud); err != nil {
+		return nil, err
+	}
+	return ud, nil
+}

pkg/util/unstructured_test.go

@@ -0,0 +1,79 @@
+// Copyright © 2019 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 implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package util
+
+import (
+	"testing"
+
+	"gotest.tools/assert"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
+	servingv1 "knative.dev/serving/pkg/apis/serving/v1"
+)
+
+func TestToUnstructuredList(t *testing.T) {
+	serviceList := servingv1.ServiceList{
+		TypeMeta: metav1.TypeMeta{
+			APIVersion: "v1",
+			Kind:       "List",
+		},
+		Items: []servingv1.Service{createService("s1"), createService("s2")},
+	}
+	expectedList := &unstructured.UnstructuredList{
+		Object: map[string]interface{}{
+			"apiVersion": string("v1"),
+			"kind":       string("List"),
+		},
+	}
+	expectedList.Items = []unstructured.Unstructured{createUnstructured("s1"), createUnstructured("s2")}
+	unstructedList, err := ToUnstructuredList(&serviceList)
+	assert.NilError(t, err)
+	assert.DeepEqual(t, unstructedList, expectedList)
+}
+
+func createService(name string) servingv1.Service {
+	service := servingv1.Service{
+		TypeMeta: metav1.TypeMeta{
+			Kind:       "Service",
+			APIVersion: "serving.knative.dev/v1",
+		},
+		ObjectMeta: metav1.ObjectMeta{
+			Name:      name,
+			Namespace: "default",
+		},
+	}
+	return service
+}
+
+func createUnstructured(name string) unstructured.Unstructured {
+	return unstructured.Unstructured{
+		Object: map[string]interface{}{
+			"apiVersion": "serving.knative.dev/v1",
+			"kind":       "Service",
+			"metadata": map[string]interface{}{
+				"namespace":         "default",
+				"name":              name,
+				"creationTimestamp": nil,
+			},
+			"spec": map[string]interface{}{
+				"template": map[string]interface{}{
+					"metadata": map[string]interface{}{"creationTimestamp": nil},
+					"spec":     map[string]interface{}{"containers": nil},
+				},
+			},
+			"status": map[string]interface{}{},
+		},
+	}
+}