Defaults for slices

[JesseOlmer]

There doesn't appear to be a way to set a default slice, as the package tries to parse as the base element type (at least for a positional argument). Is there a way to support this, even with a workaround of some kind? I'd like to be able to differentiate from having to set a default vs a user having sent in some kind of (potentially invalid) value, if possible.

package main

import (
	"github.com/alecthomas/kong"
)

var CLI struct {
	Ints []int `arg:"" required:"" default:"1,2,3" sep:","`
}

func main() {
	// CLI
	kong.Parse(&CLI)
}

error: [<ints> ...]: expected a valid 64 bit int but got "1,2,3"

[alecthomas]

Slice defaults with multiple values do indeed only work with flags at the moment. I think this is because flags support sep:"," while positional arguments don't because they're pre-separated from the shell.

I'm not sure what the right solution here is really, syntactically. It wouldn't be logical to allow sep:",", and splitting on space would preclude having an argument with a space, such as in this example:

Strs []string `arg:"" default:"foo bar"`

One option might be be to support multiple invocations of default:"X" eg. default:"1" default:"2" default:"3", though it is a bit verbose.