How can I parse flag to []any type?

[artemklevtsov]

Hi.

I tried to use the []any flag but got error:

no mapper for element type of []interface {}

Now I can parse []string, []int etc.

Code to reproduce:

package main

import (
	"fmt"

	"github.com/alecthomas/kong"
)

type CLI struct {
	Params []any `short:"p" help:"Test flag"`
}

func main() {
	cli := CLI{}

	_ = kong.Parse(&cli)

	fmt.Println(cli.Params)
}

❯ go run main.go -p 1 -p 2 -p 3
main: error: --params: no mapper for element type of []interface {}
exit status 1

Work now with:

package main

import (
	"fmt"

	"github.com/alecthomas/kong"
)

type CLI struct {
	Params []string `short:"p" help:"Test flag"`
}

func main() {
	cli := CLI{}

	_ = kong.Parse(&cli)

	fmt.Println(cli.Params)
}

❯ go run main.go -p 1 -p 2 -p 3
[1 2 3]

My final target is passing arguments to the pgx.Query which requires []any.... If I use []string all args will be quoted.

[alecthomas]

Kong doesn't support this. To do so it would have to use some kind of heuristics to detect what the input type was and parse it. For example, given the input 123a abc 123.4 Kong would probably have to try to parse each input asint float bool string in that order. I guess it's possible...

[alecthomas]

I think your best option is to parse into []string then apply the logic I describe of trying to parse each value using strconv.ParseInt() et al.