flagstruct

flagstruct

define flagset with struct and reflect

features

• Builds pflag.FlagSet by struct definition
• Supports only a single use case (shorthand of flag package)
• Nested structure support (example, shared common option)
• Default envvar support

install

$ go get -v github.com/podhmo/flagstruct

how to use

package main

import (
	"fmt"
	"os"

	"github.com/podhmo/flagstruct"
)

type Options struct {
	Name    string `flag:"name" help:"name of greeting"`
	Verbose bool   `flag:"verbose" short:"v"`
}

func main() {
	options := &Options{Name: "foo"} // default value

	flagstruct.Parse(options, func(b *flagstruct.Builder) {
		b.Name = "hello"
		b.EnvPrefix = "X_"
	})

	fmt.Printf("parsed: %#+v\n", options)
}

default help message.

$ hello --help
Usage of hello:
      --name string   ENV: X_NAME	name of greeting (default "foo")
  -v, --verbose       ENV: X_VERBOSE	-
pflag: help requested
exit status 2

run it.

$ hello --verbose
parsed: &main.Options{Name:"foo", Verbose:true}
$ hello -v --name bar
parsed: &main.Options{Name:"name", Verbose:true}

# envvar support
$ X_NAME=bar hello -v
parsed: &main.Options{Name:"bar", Verbose:true}

see also ./examples

inspired by

• https://github.com/heetch/confita
• https://github.com/AdamSLevy/flagbind