expose: Re-use labels in case none was specified

pkg/kubectl/cmd/util/factory.go

@@ -73,6 +73,8 @@ type Factory struct {
 	PodSelectorForObject func(object runtime.Object) (string, error)
 	// PortsForObject returns the ports associated with the provided object
 	PortsForObject func(object runtime.Object) ([]string, error)
+	// LabelsForObject returns the labels associated with the provided object
+	LabelsForObject func(object runtime.Object) (map[string]string, error)
 	// Returns a schema that can validate objects stored on disk.
 	Validator func() (validation.Schema, error)
 	// Returns the default namespace to use in cases where no other namespace is specified
@@ -182,6 +184,9 @@ func NewFactory(optionalClientConfig clientcmd.ClientConfig) *Factory {
 				return nil, fmt.Errorf("it is not possible to get ports from %s", kind)
 			}
 		},
+		LabelsForObject: func(object runtime.Object) (map[string]string, error) {
+			return meta.NewAccessor().Labels(object)
+		},
 		Resizer: func(mapping *meta.RESTMapping) (kubectl.Resizer, error) {
 			client, err := clients.ClientForVersion(mapping.APIVersion)
 			if err != nil {

pkg/kubectl/cmd/util/factory_test.go

@@ -23,6 +23,8 @@ import (
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/api"
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/client/clientcmd"
 	clientcmdapi "github.com/GoogleCloudPlatform/kubernetes/pkg/client/clientcmd/api"
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/kubectl"
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/runtime"
 )
 
 func TestNewFactoryDefaultFlagBindings(t *testing.T) {
@@ -100,3 +102,54 @@ func TestPortsForObject(t *testing.T) {
 		}
 	}
 }
+
+func TestLabelsForObject(t *testing.T) {
+	f := NewFactory(nil)
+
+	tests := []struct {
+		name     string
+		object   runtime.Object
+		expected string
+		err      error
+	}{
+		{
+			name: "successful re-use of labels",
+			object: &api.Service{
+				ObjectMeta: api.ObjectMeta{Name: "baz", Namespace: "test", Labels: map[string]string{"svc": "test"}},
+				TypeMeta:   api.TypeMeta{Kind: "Service", APIVersion: "v1beta3"},
+			},
+			expected: "svc=test",
+			err:      nil,
+		},
+		{
+			name: "empty labels",
+			object: &api.Service{
+				ObjectMeta: api.ObjectMeta{Name: "foo", Namespace: "test", Labels: map[string]string{}},
+				TypeMeta:   api.TypeMeta{Kind: "Service", APIVersion: "v1beta3"},
+			},
+			expected: "",
+			err:      nil,
+		},
+		{
+			name: "nil labels",
+			object: &api.Service{
+				ObjectMeta: api.ObjectMeta{Name: "zen", Namespace: "test", Labels: nil},
+				TypeMeta:   api.TypeMeta{Kind: "Service", APIVersion: "v1beta3"},
+			},
+			expected: "",
+			err:      nil,
+		},
+	}
+
+	for _, test := range tests {
+		gotLabels, err := f.LabelsForObject(test.object)
+		if err != test.err {
+			t.Fatalf("%s: Error mismatch: Expected %v, got %v", test.name, test.err, err)
+		}
+		got := kubectl.MakeLabels(gotLabels)
+		if test.expected != got {
+			t.Fatalf("%s: Labels mismatch! Expected %s, got %s", test.name, test.expected, got)
+		}
+
+	}
+}