Add kubeclt config rename-context

Enables renaming of a context via `kubectl`

Fix https://github.com/kubernetes/kubernetes/issues/45131

pkg/kubectl/cmd/config/rename_context_test.go

@@ -0,0 +1,156 @@
+/*
+Copyright 2017 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 config
+
+import (
+	"bytes"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"strings"
+	"testing"
+
+	"k8s.io/client-go/tools/clientcmd"
+	clientcmdapi "k8s.io/client-go/tools/clientcmd/api"
+)
+
+const (
+	currentContext            = "current-context"
+	newContext                = "new-context"
+	nonexistentCurrentContext = "nonexistent-current-context"
+	existentNewContext        = "existent-new-context"
+)
+
+var (
+	contextData *clientcmdapi.Context = clientcmdapi.NewContext()
+)
+
+type renameContextTest struct {
+	description    string
+	initialConfig  clientcmdapi.Config // initial config
+	expectedConfig clientcmdapi.Config // expected config
+	args           []string            // kubectl rename-context args
+	expectedOut    string              // expected out message
+	expectedErr    string              // expected error message
+}
+
+func TestRenameContext(t *testing.T) {
+	initialConfig := clientcmdapi.Config{
+		CurrentContext: currentContext,
+		Contexts:       map[string]*clientcmdapi.Context{currentContext: contextData}}
+
+	expectedConfig := clientcmdapi.Config{
+		CurrentContext: newContext,
+		Contexts:       map[string]*clientcmdapi.Context{newContext: contextData}}
+
+	test := renameContextTest{
+		description:    "Testing for kubectl config rename-context whose context to be renamed is the CurrentContext",
+		initialConfig:  initialConfig,
+		expectedConfig: expectedConfig,
+		args:           []string{currentContext, newContext},
+		expectedOut:    fmt.Sprintf("Context %q was renamed to %q.\n", currentContext, newContext),
+		expectedErr:    "",
+	}
+	test.run(t)
+}
+
+func TestRenameNonexistentContext(t *testing.T) {
+	initialConfig := clientcmdapi.Config{
+		CurrentContext: currentContext,
+		Contexts:       map[string]*clientcmdapi.Context{currentContext: contextData}}
+
+	test := renameContextTest{
+		description:    "Testing for kubectl config rename-context whose context to be renamed no exists",
+		initialConfig:  initialConfig,
+		expectedConfig: initialConfig,
+		args:           []string{nonexistentCurrentContext, newContext},
+		expectedOut:    "",
+		expectedErr:    fmt.Sprintf("cannot rename the context %q, it's not in", nonexistentCurrentContext),
+	}
+	test.run(t)
+}
+
+func TestRenameToAlreadyExistingContext(t *testing.T) {
+	initialConfig := clientcmdapi.Config{
+		CurrentContext: currentContext,
+		Contexts: map[string]*clientcmdapi.Context{
+			currentContext:     contextData,
+			existentNewContext: contextData}}
+
+	test := renameContextTest{
+		description:    "Testing for kubectl config rename-context whose the new name is already in another context.",
+		initialConfig:  initialConfig,
+		expectedConfig: initialConfig,
+		args:           []string{currentContext, existentNewContext},
+		expectedOut:    "",
+		expectedErr:    fmt.Sprintf("cannot rename the context %q, the context %q already exists", currentContext, existentNewContext),
+	}
+	test.run(t)
+}
+
+func (test renameContextTest) run(t *testing.T) {
+	fakeKubeFile, _ := ioutil.TempFile("", "")
+	defer os.Remove(fakeKubeFile.Name())
+	err := clientcmd.WriteToFile(test.initialConfig, fakeKubeFile.Name())
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+
+	pathOptions := clientcmd.NewDefaultPathOptions()
+	pathOptions.GlobalFile = fakeKubeFile.Name()
+	pathOptions.EnvVar = ""
+	options := RenameContextOptions{
+		configAccess: pathOptions,
+		contextName:  test.args[0],
+		newName:      test.args[1],
+	}
+	buf := bytes.NewBuffer([]byte{})
+	cmd := NewCmdConfigRenameContext(buf, options.configAccess)
+
+	options.Complete(cmd, test.args, buf)
+	options.Validate()
+	err = options.RunRenameContext(buf)
+
+	if len(test.expectedErr) != 0 {
+		if err == nil {
+			t.Errorf("Did not get %v", test.expectedErr)
+		} else {
+			if !strings.Contains(err.Error(), test.expectedErr) {
+				t.Errorf("Expected error %v, but got %v", test.expectedErr, err)
+			}
+		}
+		return
+	}
+
+	config, err := clientcmd.LoadFromFile(fakeKubeFile.Name())
+	if err != nil {
+		t.Fatalf("unexpected error loading kubeconfig file: %v", err)
+	}
+
+	_, oldExists := config.Contexts[currentContext]
+	_, newExists := config.Contexts[newContext]
+
+	if (!newExists) || (oldExists) || (config.CurrentContext != newContext) {
+		t.Errorf("Failed in: %q\n expected %v\n but got %v", test.description, test.expectedConfig, *config)
+	}
+
+	if len(test.expectedOut) != 0 {
+		if buf.String() != test.expectedOut {
+			t.Errorf("Failed in:%q\n expected out %v\n but got %v", test.description, test.expectedOut, buf.String())
+		}
+	}
+}