Order of processing

[stevewi-niteflyte]

I am using v3. I'm having an issue with global flags not being validated before a sub-command's Action: is invoked.

I have a global flag, --debug, that takes an integer in the range 0..5. The value is is validated in the Action: for the application:

$ a2m -D 7
a2m: [ERROR] --debug must be in the range 0..5.

However, in the Action: for a sub-command, this doesn't happen (show is a Command: and conf is a sub-Command:):

$ a2m -D 7 show conf a
Show conf: a <- temporary sub-Command: Action: output

Why isn't the Action: for the application invoked in this case? In the sub-Command: example, I would have expected the error message. Maybe I'm jaded by my experience with Ruby thor doing this automagically... ;-)

Do I have to explicitly invoke the application Action: in the Action: for the sub-Command:? If so, how do I do that...or
do I have to restructure my code a bit and eliminate the application Action:?

Thanks in advance...

[tentechle]

The root command's Action handles running the root command itself. When you select show conf, the handler that runs is that subcommand's Action; the parent Action functions aren't called along the way.

For this range check, put the validation on your root IntFlag:

&cli.IntFlag{
    Name:    "debug",
    Aliases: []string{"D"},
    Value:   0,
    Action: func(ctx context.Context, cmd *cli.Command, value int) error {
        if value < 0 || value > 5 {
            return fmt.Errorf("--debug must be in the range 0..5")
        }
        return nil
    },
},

This uses context and fmt from the standard library. An error returned by the flag action stops execution before the selected command's Action, so you don't need to invoke the application's action manually.

I checked this with v3.14.0 using a root command with nested show / conf commands: both a2m -D 7 and a2m -D 7 show conf a reject the value; a2m -D 5 show conf a reaches the subcommand. Negative values are rejected too.

Flag actions run when the flag is set. If you need validation or setup on every invocation, including when the default is used, put that in the root command's Before hook instead. The ancestor Before hooks run for subcommands as well. Here your default of 0 is already valid.

Reference: v3 flag actions.

[stevewi-niteflyte]

Thank you so much! I suspected that I was jaded by Ruby thor... where application actions ALWAYS happen before the command actions. Anyway, this works perfectly. FWIW, the debug value is a uint8 so no need to check for negative values.

Thank you again!