Custom validators do not run for envars

[dreamscached]

Hello! I want to validate an input URL and I did that per this section in the README. However, it doesn't seem that MyURL#Validate is ever getting invoked. What am I doing wrong?

type MyURL url.URL

func (u *MyURL) Validate() error {
	if u.Host != "example.com" {
		return errors.New("not an example.com URL")
	}
	return nil
}

var args struct {
	URL    []*url.URL `arg:"" help:"List of URL."`
	Folder string     `arg:"" optional:"" help:"Output folder.`
}

func main() {
	kong.Parse(&args)
}

[alecthomas]

You're not using your MyURL type in args.

[alecthomas]

BTW this probably won't parse correctly, because your type alias doesn't have its TextUnmarshaler method. Go type aliases don't retain the original type's methods.

[dreamscached]

I feel so dumb now that I didn't even check if I use my type... Anyway, much appreciated!

[mwmahlberg]

I am not quite sure, but this seems to be related. When trying to custom-validate an enum (I neither can have default air required set on this), there is no validation error in this code.

The TextUnmarshalerworks fine, since any arbitrary value for Hoststate is accepted.

Of course I could do the validation in UnmarshalText (tested, works fine, ofc), but that seems rather ugly to me.

Am I missing something here?

type HostState string

func (hs HostState) Validate() error {
        // For Illustration purposes
	fmt.Println("Not printed")
	switch hs {
	case Up, Down, Unreachable:
		return nil
	default:
		return errors.New("Must be UP, DOWN or UNREACH")
	}
}

func (hs *HostState) UnmarshalText(in []byte) error {
	*hs = HostState(string(in))
	return nil
}

const (
	Up          HostState = "UP"
	Down        HostState = "DOWN"
	Unreachable HostState = "UNREACH"
)

type config struct {
	HostState HostState `env:"HOSTSTATE" default:"DOWN"`
}

var cli config

func main() {
	ctx := kong.Parse(&cli)
	ctx.Printf("Config: %#v", cli)
}

[alecthomas]

Does making it a pointer receiver fix it?

[mwmahlberg]

No, Sir! Forgot to mention that I checked that, too. Rechecked now - does not make a difference.

[alecthomas]

This seems to work fine for me:
https://go.dev/play/p/QHiLtLPAjzz

[mwmahlberg]

It seems to be a problem with environment variables:
https://go.dev/play/p/E4WbmsyUfr3

[mwmahlberg]

@alecthomas I think this is a bug.

As per above code, custom validators for environment variables are not triggered. Shall I open a new bug ticket on this?

I will dig into the code and try to provide a PR in any case.

[alecthomas]

Yep I think it is a bug too. A PR would be welcome, thanks.

[alecthomas]

One challenge might be that envars are unfortunately special cased in Kong, so fixing it might be a bit of an issue. I have been meaning to fix the underlying issue for a while, but it's generally not been too much of a problem so it's been low priority.

[alecthomas]

Actually yeah, a new issue would be preferable thanks.

[mitar]

I do not think any issue (or fix) has been made for this?

[mitar]

I made #390 as a followup.