jsonflag

jsonflag is a tiny Go library that can turn any JSON-marshallable struct into a set of command‑line flags. It works with the standard flag package and with the popular pflag package, handling nested structs, slices, maps and pointer fields automatically.

Adding to project

First, use go get to download and add the latest version of the library to the project.

go get -u github.com/daishe/jsonflag

Then include in your source code.

import "github.com/daishe/jsonflag"

Usage example (with standard go flag package)

package main

import (
	"flag"
	"fmt"
	"net/http"
	"net/http/httputil"
	"net/url"
	"os"

	"github.com/daishe/jsonflag"
)

func main() {
	config := struct {
		URL struct {
			Scheme string `json:"scheme"`
			Host   string `json:"host"`
			Port   int    `json:"port"`
			Path   string `json:"path"`
		} `json:"url"`
		Verbose bool `json:"verbose"`
	}{}

	// default values
	config.URL.Scheme = "https"
	config.URL.Host = "localhost"
	config.URL.Port = 8080

	fs := flag.NewFlagSet("", flag.ExitOnError) // you can also add it directly to the root flag set
	for _, val := range jsonflag.Recursive(&config) {
		fs.Var(val, jsonflag.JSONName(val.Path()), jsonflag.Usage(val.Path()))
	}
	if err := fs.Parse(os.Args[1:]); err != nil {
		fmt.Fprintf(os.Stderr, "Arguments parsing error: %v\n", err)
		os.Exit(1)
	}

	u := url.URL{
		Scheme: config.URL.Scheme,
		Host:   fmt.Sprintf("%s:%d", config.URL.Host, config.URL.Port),
		Path:   config.URL.Path,
	}

	resp, err := http.Get(u.String())
	if err != nil {
		fmt.Fprintf(os.Stderr, "Doing request error: %v\n", err)
		os.Exit(1)
	}
	defer resp.Body.Close()

	if config.Verbose {
		respBytes, err := httputil.DumpResponse(resp, true)
		if err != nil {
			fmt.Fprintf(os.Stderr, "Dumping response error: %v\n", err)
			os.Exit(1)
		}
		fmt.Printf("%s\n", respBytes)
	}
}

License

The project is released under the Apache License, Version 2.0. See the full LICENSE file for the complete terms and conditions.