Move unrelated methods from the factory to helper

pkg/kubectl/polymorphichelpers/mapbasedselectorforobject.go

@@ -0,0 +1,63 @@
+/*
+Copyright 2018 The Kubernetes 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 polymorphichelpers
+
+import (
+	"fmt"
+
+	"k8s.io/apimachinery/pkg/runtime"
+	api "k8s.io/kubernetes/pkg/apis/core"
+	"k8s.io/kubernetes/pkg/apis/extensions"
+	"k8s.io/kubernetes/pkg/kubectl"
+)
+
+// mapBasedSelectorForObject returns the map-based selector associated with the provided object. If a
+// new set-based selector is provided, an error is returned if the selector cannot be converted to a
+// map-based selector
+func mapBasedSelectorForObject(object runtime.Object) (string, error) {
+	// TODO: replace with a swagger schema based approach (identify pod selector via schema introspection)
+	switch t := object.(type) {
+	case *api.ReplicationController:
+		return kubectl.MakeLabels(t.Spec.Selector), nil
+	case *api.Pod:
+		if len(t.Labels) == 0 {
+			return "", fmt.Errorf("the pod has no labels and cannot be exposed")
+		}
+		return kubectl.MakeLabels(t.Labels), nil
+	case *api.Service:
+		if t.Spec.Selector == nil {
+			return "", fmt.Errorf("the service has no pod selector set")
+		}
+		return kubectl.MakeLabels(t.Spec.Selector), nil
+	case *extensions.Deployment:
+		// TODO(madhusudancs): Make this smarter by admitting MatchExpressions with Equals
+		// operator, DoubleEquals operator and In operator with only one element in the set.
+		if len(t.Spec.Selector.MatchExpressions) > 0 {
+			return "", fmt.Errorf("couldn't convert expressions - \"%+v\" to map-based selector format", t.Spec.Selector.MatchExpressions)
+		}
+		return kubectl.MakeLabels(t.Spec.Selector.MatchLabels), nil
+	case *extensions.ReplicaSet:
+		// TODO(madhusudancs): Make this smarter by admitting MatchExpressions with Equals
+		// operator, DoubleEquals operator and In operator with only one element in the set.
+		if len(t.Spec.Selector.MatchExpressions) > 0 {
+			return "", fmt.Errorf("couldn't convert expressions - \"%+v\" to map-based selector format", t.Spec.Selector.MatchExpressions)
+		}
+		return kubectl.MakeLabels(t.Spec.Selector.MatchLabels), nil
+	default:
+		return "", fmt.Errorf("cannot extract pod selector from %T", object)
+	}
+}