kubectl源码分析之explain_kubtl explain-优快云博客

type ExplainOptions struct {//explain结构体
	genericclioptions.IOStreams

	CmdParent  string
	APIVersion string
	Recursive  bool

	Mapper meta.RESTMapper
	Schema openapi.Resources
}

func NewExplainOptions(parent string, streams genericclioptions.IOStreams) *ExplainOptions {
	return &ExplainOptions{//初始化explain结构体
		IOStreams: streams,
		CmdParent: parent,
	}
}

//创建explain命令
func NewCmdExplain(parent string, f cmdutil.Factory, streams genericclioptions.IOStreams) *cobra.Command {
	o := NewExplainOptions(parent, streams)//初始化结构体

	cmd := &cobra.Command{//创建cobra命令
		Use:                   "explain RESOURCE",
		DisableFlagsInUseLine: true,
		Short:                 i18n.T("Documentation of resources"),
		Long:                  explainLong + "\n\n" + cmdutil.SuggestAPIResources(parent),
		Example:               explainExamples,
		Run: func(cmd *cobra.Command, args []string) {
			cmdutil.CheckErr(o.Complete(f, cmd))//准备
			cmdutil.CheckErr(o.Validate(args))//校验
			cmdutil.CheckErr(o.Run(args))//运行
		},
	}
	cmd.Flags().BoolVar(&o.Recursive, "recursive", o.Recursive, "Print the fields of fields (Currently only 1 level deep)")//recursive选项
	cmd.Flags().StringVar(&o.APIVersion, "api-version", o.APIVersion, "Get different explanations for particular API version")//api-version选项
	return cmd
}

//准备方法
func (o *ExplainOptions) Complete(f cmdutil.Factory, cmd *cobra.Command) error {
	var err error
	o.Mapper, err = f.ToRESTMapper()//设置mapper
	if err != nil {
		return err
	}

	o.Schema, err = f.OpenAPISchema()//设置schema
	if err != nil {
		return err
	}
	return nil
}

//校验
func (o *ExplainOptions) Validate(args []string) error {
	if len(args) == 0 {//参数不能为空
		return fmt.Errorf("You must specify the type of resource to explain. %s\n", cmdutil.SuggestAPIResources(o.CmdParent))
	}
	if len(args) > 1 {//参数不能大于一个
		return fmt.Errorf("We accept only this format: explain RESOURCE\n")
	}

	return nil
}

//运行
func (o *ExplainOptions) Run(args []string) error {
	recursive := o.Recursive
	apiVersionString := o.APIVersion

	// TODO: After we figured out the new syntax to separate group and resource, allow
	// the users to use it in explain (kubectl explain <group><syntax><resource>).
	// Refer to issue #16039 for why we do this. Refer to PR #15808 that used "/" syntax.
	inModel, fieldsPath, err := explain.SplitAndParseResourceRequest(args[0], o.Mapper)//用.分割resource和字段
	if err != nil {
		return err
	}

	// TODO: We should deduce the group for a resource by discovering the supported resources at server.
	fullySpecifiedGVR, groupResource := schema.ParseResourceArg(inModel)//解析groupversionresource
	gvk := schema.GroupVersionKind{}
	if fullySpecifiedGVR != nil {
		gvk, _ = o.Mapper.KindFor(*fullySpecifiedGVR)//从gvr获取gvk
	}
	if gvk.Empty() {//如果gvk为空，则获取版本为空的gvk
		gvk, err = o.Mapper.KindFor(groupResource.WithVersion(""))
		if err != nil {
			return err
		}
	}

	if len(apiVersionString) != 0 {//如果api-version不为空，则再次获取gvk
		apiVersion, err := schema.ParseGroupVersion(apiVersionString)
		if err != nil {
			return err
		}
		gvk = apiVersion.WithKind(gvk.Kind)
	}

	schema := o.Schema.LookupResource(gvk)//获取schema
	if schema == nil {
		return fmt.Errorf("Couldn't find resource for %q", gvk)
	}

	return explain.PrintModelDescription(fieldsPath, o.Out, schema, gvk, recursive)//打印结果
}