Participle

participle.go

package main

import (
	"fmt"

	"github.com/alecthomas/participle"
	"github.com/alecthomas/repr"
)

type CLI struct {
	Entries []*Entry `{ @@ }`
}

type Entry struct {
	Usage    string     `  "usage" ":" @String`
	Commands []*Command `| "commands" ":" { @@ }`
	Flags    []*Flag    `| "flags" ":" { @@ }`
}

type Command struct {
	Long        string `@Ident`
	Comma       string `","`
	Short       string `@Ident`
	Description string `@String`
}

type Flag struct {
	Long        string `"-" "-" @Ident`
	Comma       string `","`
	Short       string `"-" "-" @Ident`
	Description string `@String`
}

func main() {
	parser, err := participle.Build(&CLI{})
	if err != nil {
		panic(err)
	}
	ast := &CLI{}

	err = parser.ParseString(`
usage: "my usage"

commands:
	long, short    "description"
	long2, short2  "description2"

flags:
	--long, --short    "description"
`, ast)
	if err != nil {
		fmt.Println(err)
	}

	repr.Println(ast)
}