PreRun / PreRunE 钩子未在 cobra 中执行

Question

I have a cobra command

var mycommandCmd = &cobra.Command{
    Use:   "mycommand",
    PersistentPreRunE: func(cmd *cobra.Command, args []string) error {
        viper.BindPFlags(cmd.Flags())

and a subcommand

var mysubcommandCmd = &cobra.Command{
    Use:   "mysubcommand",
    Args:  cobra.ExactArgs(1),
    PreRun: func(cmd *cobra.Command, args []string) {
        fmt.Println("HELLO")
    },
    RunE: func(cmd *cobra.Command, args []string) error {
        viper.BindPFlags(cmd.Flags())

However I don't see the PreRun hook being executed when there is an error in terms of argument passing.

In the case above, mysubcommand requires exactly one argument, so when invoking it without it:

go run main.go mycommand mysubcommand

Error: accepts 1 arg(s), received 0
Usage:
  myprog mycommand mysubcommand [flags]

FWIW what I am trying to do is to print a more elegant and informative message in case the argument count is wrong.

Same is the situation when using PreRunE in the place of PreRun

Answer 1

From what I understand working with the library so far is that, there is a validation done before execution of PreRun hooks. Since you have mentioned Args: cobra.ExactArgs(1) , the validation fails causing the error.
Docs .

If you want to handle this by yourself, you should do something like this in your mysubcommandCmd

var mysubcommandCmd = &cobra.Command{
    Use:   "mysubcommand",
    PreRunE: func(cmd *cobra.Command, args []string) {
        if len(args) != 1 {
            return errors.New("more elegant and informative message")
        }
        fmt.Println("HELLO")
        return nil
    },