kubectl源码分析之completion

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 目前刚开始写一个月，一共写了18篇原创文章，文章目录如下：

istio多集群探秘，部署了50次多集群后我得出的结论

istio多集群链路追踪，附实操视频

istio防故障利器，你知道几个,istio新手不要读，太难！

istio业务权限控制，原来可以这么玩

istio实现非侵入压缩，微服务之间如何实现压缩

不懂envoyfilter也敢说精通istio系列-http-rbac-不要只会用AuthorizationPolicy配置权限

不懂envoyfilter也敢说精通istio系列-02-http-corsFilter-不要只会vs

不懂envoyfilter也敢说精通istio系列-03-http-csrf filter-再也不用再代码里写csrf逻辑了

不懂envoyfilter也敢说精通istio系列http-jwt_authn-不要只会RequestAuthorization

不懂envoyfilter也敢说精通istio系列-05-fault-filter-故障注入不止是vs

不懂envoyfilter也敢说精通istio系列-06-http-match-配置路由不只是vs

不懂envoyfilter也敢说精通istio系列-07-负载均衡配置不止是dr

不懂envoyfilter也敢说精通istio系列-08-连接池和断路器

不懂envoyfilter也敢说精通istio系列-09-http-route filter

不懂envoyfilter也敢说精通istio系列-network filter-redis proxy

不懂envoyfilter也敢说精通istio系列-network filter-HttpConnectionManager

不懂envoyfilter也敢说精通istio系列-ratelimit-istio ratelimit完全手册

 

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var (//支持的shell及函数
	completionShells = map[string]func(out io.Writer, boilerPlate string, cmd *cobra.Command) error{
		"bash": runCompletionBash,
		"zsh":  runCompletionZsh,
	}
)

//创建completion命令
func NewCmdCompletion(out io.Writer, boilerPlate string) *cobra.Command {
	shells := []string{}
	for s := range completionShells {
		shells = append(shells, s)
	}

	cmd := &cobra.Command{//创建cobra命令
		Use:                   "completion SHELL",
		DisableFlagsInUseLine: true,
		Short:                 i18n.T("Output shell completion code for the specified shell (bash or zsh)"),
		Long:                  completionLong,
		Example:               completionExample,
		Run: func(cmd *cobra.Command, args []string) {
			err := RunCompletion(out, boilerPlate, cmd, args)//运行
			cmdutil.CheckErr(err)
		},
		ValidArgs: shells,//有效参数
	}

	return cmd
}

//运行
func RunCompletion(out io.Writer, boilerPlate string, cmd *cobra.Command, args []string) error {
	if len(args) == 0 {//参数不能是0个
		return cmdutil.UsageErrorf(cmd, "Shell not specified.")
	}
	if len(args) > 1 {//参数不能大于1个
		return cmdutil.UsageErrorf(cmd, "Too many arguments. Expected only the shell type.")
	}
	run, found := completionShells[args[0]]//获取运行函数
	if !found {
		return cmdutil.UsageErrorf(cmd, "Unsupported shell type %q.", args[0])
	}

	return run(out, boilerPlate, cmd.Parent())//运行
}

//运行bash completion
func runCompletionBash(out io.Writer, boilerPlate string, kubectl *cobra.Command) error {
	if len(boilerPlate) == 0 {//设置license
		boilerPlate = defaultBoilerPlate
	}
	if _, err := out.Write([]byte(boilerPlate)); err != nil {//输出license
		return err
	}

	return kubectl.GenBashCompletion(out)//产生命令补全
}

//产生命令补全
func (c *Command) GenBashCompletion(w io.Writer) error {
	buf := new(bytes.Buffer)//创建buffer
	writePreamble(buf, c.Name())//写序言
	if len(c.BashCompletionFunction) > 0 {//如果有BashCompletionFunction函数，则写函数
		buf.WriteString(c.BashCompletionFunction + "\n")
	}
	gen(buf, c)//写具体命令
	writePostscript(buf, c.Name())//写post脚本

	_, err := buf.WriteTo(w)//buffer写到writer里
	return err
}

//递归调用写命令completion
func gen(buf *bytes.Buffer, cmd *Command) {
	for _, c := range cmd.Commands() {//遍历命令
		if !c.IsAvailableCommand() || c == cmd.helpCommand {
			continue
		}
		gen(buf, c)//递归调用
	}
	commandName := cmd.CommandPath()//获取命令名称
	commandName = strings.Replace(commandName, " ", "_", -1)
	commandName = strings.Replace(commandName, ":", "__", -1)

	if cmd.Root() == cmd {//命令是root命令
		buf.WriteString(fmt.Sprintf("_%s_root_command()\n{\n", commandName))
	} else {
		buf.WriteString(fmt.Sprintf("_%s()\n{\n", commandName))
	}

	buf.WriteString(fmt.Sprintf("    last_command=%q\n", commandName))
	buf.WriteString("\n")
	buf.WriteString("    command_aliases=()\n")
	buf.WriteString("\n")

	writeCommands(buf, cmd)//写命令
	writeFlags(buf, cmd)//写flags
	writeRequiredFlag(buf, cmd)//写reuqiredflag
	writeRequiredNouns(buf, cmd)//写requiredNouns
	writeArgAliases(buf, cmd)//写别名
	buf.WriteString("}\n\n")
}