Merge pull request #27049 from andreykurilin/kubectl_help

Automatic merge from submit-queue

Implement custom help command for kubectl

```release-note
* kubectl help now provides "Did you mean this?" suggestions for typo/invalid command names.
```

Custom implementation of help command allows to print `Did you mean this?` with
suggestions, which is missed in embed help command from github.com/spf13/cobra

Also, it can be extended with different search features. At this patch, help
command searches query in short descriptions of commands in case of mismatch
with commands names.

fixes #25234

pkg/kubectl/cmd/cmd.go

@@ -198,6 +198,8 @@ Find more information at https://github.com/kubernetes/kubernetes.`,
 	f.BindFlags(cmds.PersistentFlags())
 	f.BindExternalFlags(cmds.PersistentFlags())
 
+	cmds.SetHelpCommand(NewCmdHelp(f, out))
+
 	// From this point and forward we get warnings on flags that contain "_" separators
 	cmds.SetGlobalNormalizationFunc(flag.WarnWordSepNormalizeFunc)
 

pkg/kubectl/cmd/help.go

@@ -0,0 +1,79 @@
+/*
+Copyright 2016 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 cmd
+
+import (
+	"io"
+	"strings"
+
+	"github.com/spf13/cobra"
+
+	cmdutil "k8s.io/kubernetes/pkg/kubectl/cmd/util"
+)
+
+const help_long = `Help provides help for any command in the application.
+Simply type kubectl help [path to command] for full details.`
+
+func NewCmdHelp(f *cmdutil.Factory, out io.Writer) *cobra.Command {
+	cmd := &cobra.Command{
+		Use:   "help [command] | STRING_TO_SEARCH",
+		Short: "Help about any command",
+		Long:  help_long,
+
+		Run: RunHelp,
+	}
+
+	return cmd
+}
+
+func RunHelp(cmd *cobra.Command, args []string) {
+	foundCmd, a, err := cmd.Root().Find(args)
+
+	// NOTE(andreykurilin): actually, I did not find any cases when foundCmd can be nil,
+	//   but let's make this check since it is included in original code of initHelpCmd
+	//   from github.com/spf13/cobra
+	if foundCmd == nil {
+		cmd.Printf("Unknown help topic %#q.\n", args)
+		cmd.Root().Usage()
+	} else if err != nil {
+		// print error message at first, since it can contain suggestions
+		cmd.Println(err)
+
+		argsString := strings.Join(args, " ")
+		var matchedMsgIsPrinted bool = false
+		for _, foundCmd := range foundCmd.Commands() {
+			if strings.Contains(foundCmd.Short, argsString) {
+				if !matchedMsgIsPrinted {
+					cmd.Printf("Matchers of string '%s' in short descriptions of commands: \n", argsString)
+					matchedMsgIsPrinted = true
+				}
+				cmd.Printf("  %-14s %s\n", foundCmd.Name(), foundCmd.Short)
+			}
+		}
+
+		if !matchedMsgIsPrinted {
+			// if nothing is found, just print usage
+			cmd.Root().Usage()
+		}
+	} else if len(a) == 0 {
+		// help message for help command :)
+		cmd.Root().Usage()
+	} else {
+		helpFunc := foundCmd.HelpFunc()
+		helpFunc(foundCmd, args)
+	}
+}