Purposely call usage after argument validation,

[gavinmcnair]

I am trying to get the usage message when failing to validate arguments passed

arg.WriteHelp(os.Stdout)

does not work and is not really relevant without the &args struct.

What is the best way to purposely call usage?

[alexflint]

one way you can do this is with this sample:

var args struct {
	Foo string
	Bar string
}
p := arg.MustParse(&args)
if args.Foo == "" && args.Bar == "" {
	p.Fail("you must provide either --foo or --bar")
}

output is:

./example
Usage: samples [--foo FOO] [--bar BAR]
error: you must provide either --foo or --bar

Is this what you want?

(Also, in what way does p.WriteHelp(os.Stdout) not work?)

[alexflint]

Closing for now, feel free to reopen if this does not solve your problem

[gavinmcnair]

Perfect, i wasn't capturing p (in your example). This works great now. Thanks