Simple CLI with no subcommand?

[tnarg]

Is it possible to write a simple CLI with no subcommand in kong. For example, how would you write the equivalent of

package main

import (
	"flag"
	"fmt"
)

var verbose bool

func init() {
	flag.BoolVar(&verbose, "verbose", false, "print some extra stuff")
}

func main() {
	flag.Parse()
	if verbose {
		fmt.Println("blah")
	}
	fmt.Println("Hello, playground")
}

[alecthomas]

Absolutely:

package main

import (
	"fmt"

	"github.com/alecthomas/kong"
)

var cli struct {
  Verbose bool `help:"print some extra stuff"`
}

func main() {
	kong.Parse()
	if cli.Verbose {
		fmt.Println("blah")
	}
	fmt.Println("Hello, playground")
}

[tnarg]

Okay great! Now for a slightly more complicated example:

package main

import (
	"fmt"
	"io"
	"os"

	"github.com/alecthomas/kong"
)

type CLI struct {
	Verbose bool `help:"print some extra stuff"`
}

func (cli *CLI) Run(w io.Writer) {
	if cli.Verbose {
		fmt.Fprintln(w, "blah")
	}
	fmt.Fprintln(w, "Hello, playground")
}

func main() {
	var cli CLI
	ctx := kong.Parse(&cli)
	ctx.BindTo(os.Stdout, (*io.Writer)(nil))
	if err := ctx.Run(); err != nil {
		panic(err)
	}
}

When I try this, I get

panic: no command selected

I was hoping that CLI would act as the root command.

[alecthomas]

That's correct, Run() currently only works if you have commands. That said it would be more consistent to work in this case too.

[alecthomas]

Also, hey again Grant :)