Fix kubectl version should print version info

Author: zhouya0

staging/src/k8s.io/cli-runtime/pkg/genericclioptions/config_flags.go

@@ -17,7 +17,6 @@ limitations under the License.
 package genericclioptions
 
 import (
-	"errors"
 	"os"
 	"path/filepath"
 	"regexp"
@@ -58,8 +57,7 @@ const (
 
 var (
 	defaultCacheDir = filepath.Join(homedir.HomeDir(), ".kube", "http-cache")
-
-	ErrEmptyConfig = errors.New(`Missing or incomplete configuration info.  Please point to an existing, complete config file:
+	ErrEmptyConfig  = clientcmd.NewEmptyConfigError(`Missing or incomplete configuration info.  Please point to an existing, complete config file:
 
   1. Via the command-line flag --kubeconfig
   2. Via the KUBECONFIG environment variable

staging/src/k8s.io/client-go/tools/clientcmd/validation.go

@@ -30,11 +30,24 @@ import (
 
 var (
 	ErrNoContext   = errors.New("no context chosen")
-	ErrEmptyConfig = errors.New("no configuration has been provided, try setting KUBERNETES_MASTER environment variable")
+	ErrEmptyConfig = NewEmptyConfigError("no configuration has been provided, try setting KUBERNETES_MASTER environment variable")
 	// message is for consistency with old behavior
 	ErrEmptyCluster = errors.New("cluster has no server defined")
 )
 
+// NewEmptyConfigError returns an error wrapping the given message which IsEmptyConfig() will recognize as an empty config error
+func NewEmptyConfigError(message string) error {
+	return &errEmptyConfig{message}
+}
+
+type errEmptyConfig struct {
+	message string
+}
+
+func (e *errEmptyConfig) Error() string {
+	return e.message
+}
+
 type errContextNotFound struct {
 	ContextName string
 }
@@ -60,9 +73,14 @@ func IsContextNotFound(err error) bool {
 func IsEmptyConfig(err error) bool {
 	switch t := err.(type) {
 	case errConfigurationInvalid:
-		return len(t) == 1 && t[0] == ErrEmptyConfig
+		if len(t) != 1 {
+			return false
+		}
+		_, ok := t[0].(*errEmptyConfig)
+		return ok
 	}
-	return err == ErrEmptyConfig
+	_, ok := err.(*errEmptyConfig)
+	return ok
 }
 
 // errConfigurationInvalid is a set of errors indicating the configuration is invalid.

staging/src/k8s.io/kubectl/pkg/cmd/version/BUILD

@@ -1,4 +1,4 @@
-load("@io_bazel_rules_go//go:def.bzl", "go_library")
+load("@io_bazel_rules_go//go:def.bzl", "go_library", "go_test")
 
 go_library(
     name = "go_default_library",
@@ -20,6 +20,16 @@ go_library(
     ],
 )
 
+go_test(
+    name = "go_default_test",
+    srcs = ["version_test.go"],
+    embed = [":go_default_library"],
+    deps = [
+        "//staging/src/k8s.io/cli-runtime/pkg/genericclioptions:go_default_library",
+        "//staging/src/k8s.io/kubectl/pkg/cmd/util:go_default_library",
+    ],
+)
+
 filegroup(
     name = "package-srcs",
     srcs = glob(["**"]),

staging/src/k8s.io/kubectl/pkg/cmd/version/version_test.go

@@ -0,0 +1,38 @@
+/*
+Copyright 2020 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 version
+
+import (
+	"strings"
+	"testing"
+
+	"k8s.io/cli-runtime/pkg/genericclioptions"
+	cmdutil "k8s.io/kubectl/pkg/cmd/util"
+)
+
+func TestNewCmdVersionWithoutConfigFile(t *testing.T) {
+	tf := cmdutil.NewFactory(&genericclioptions.ConfigFlags{})
+	streams, _, buf, _ := genericclioptions.NewTestIOStreams()
+	cmd := NewCmdVersion(tf, streams)
+	cmd.SetOutput(buf)
+	if err := cmd.Execute(); err != nil {
+		t.Errorf("Cannot execute version command: %v", err)
+	}
+	if !strings.Contains(buf.String(), "Client Version") {
+		t.Errorf("unexpected output: %s", buf.String())
+	}
+}