Ra

Quick Start

go get github.com/amterp/ra

package main
import (
	"fmt"
	"os"
	"github.com/amterp/ra"
)
func main() {
	cmd := ra.NewCmd("myapp")
	// This arg works both positionally AND as a flag
	input, _ := ra.NewString("input").Register(cmd)
	format, _ := ra.NewString("format").SetDefault("json").Register(cmd)
	verbose, _ := ra.NewBool("verbose").SetShort("v").Register(cmd)
	cmd.ParseOrExit(os.Args[1:])
	fmt.Printf("Input: %s, Format: %s, Verbose: %t\n", *input, *format, *verbose)
}

myapp data.txt json --verbose # positional style
myapp --input data.txt --format json -v # flag style 

Key Features

Why Ra?

// Cobra: Separate definitions for flags and positional args
cmd.Flags().StringVarP(&input, "input", "i", "", "input file")
cmd.Args = cobra.ExactArgs(1) // The positional arg is separate
// Ra: A single declaration enables both styles 
input, _ := ra.NewString("input").Register(cmd)
// User can use `myapp file.txt` OR `myapp --input file.txt`

Example

package main
import (
	"fmt"
	"os"
	"github.com/amterp/ra"
)
func main() {
	cmd := ra.NewCmd("fileproc")
	cmd.SetDescription("A file processor with various output formats")
	// Required input file (positional or --input)
	input, _ := ra.NewString("input").Register(cmd)
	// Format with enum constraint and default
	format, _ := ra.NewString("format").
		SetShort("f").
		SetDefault("json").
		SetEnumConstraint([]string{"json", "xml", "yaml"}).
		Register(cmd)
	// Timeout with range constraint
	timeout, _ := ra.NewInt("timeout").
		SetDefault(30).
		SetMin(1, true).SetMax(300, true).
		Register(cmd)
	// Mutually exclusive flags
	verbose, _ := ra.NewBool("verbose").
		SetShort("v").
		SetExcludes([]string{"quiet"}).
		Register(cmd)
	quiet, _ := ra.NewBool("quiet").
		SetShort("q").
		SetExcludes([]string{"verbose"}).
		Register(cmd)
	// Variadic tags
	tags, _ := ra.NewStringSlice("tags").
		SetVariadic(true).
		SetOptional(true).
		Register(cmd)
	// Subcommand
	validateCmd := ra.NewCmd("validate")
	validateInput, _ := ra.NewString("input").Register(validateCmd)
	strict, _ := ra.NewBool("strict").Register(validateCmd)
	validateUsed, _ := cmd.RegisterCmd(validateCmd)
	// Parse
	err := cmd.ParseOrError(os.Args[1:])
	if err == ra.HelpInvokedErr {
		return // Help was shown
	} else if err != nil {
		fmt.Fprintf(os.Stderr, "Error: %v\n", err)
		os.Exit(1)
	}
	// Handle subcommand
	if *validateUsed {
		fmt.Printf("Validating: %s (strict: %t)\n", *validateInput, *strict)
		return
	}
	// Main processing
	fmt.Printf("Processing %s -> %s format (timeout: %ds)\n",
		*input, *format, *timeout)
	if *verbose {
		fmt.Println("Verbose mode enabled")
	} else if *quiet {
		fmt.Println("Quiet mode enabled")
	}
	if len(*tags) > 0 {
		fmt.Printf("Tags: %v\n", *tags)
	}
}

# All equivalent ways to call the same thing:
fileproc data.txt # positional
fileproc --input data.txt # flag style
fileproc data.txt --format xml -v # mixed style
fileproc data.txt xml 60 --tags api,prod # mostly positional
# Subcommand
fileproc validate config.json --strict
# Auto-generated help
fileproc --help
# Output:
# A file processor with various output formats
#
# Usage:
# fileproc [validate] <input> [format] [timeout] [OPTIONS]
#
# Commands:
# validate
#
# Arguments:
# --input str 
# -f, --format str Default: json. Valid values: [json, xml, yaml]
# --timeout int Default: 30. Range: [1, 300]
# -v, --verbose Excludes: quiet
# -q, --quiet Excludes: verbose 
# --tags [strs...] (optional)
# -h, --help Print usage information
# Constraint validation errors
fileproc data.txt --format csv
# Output: Error: Invalid 'format' value: csv (valid values: json, xml, yaml)
fileproc data.txt --timeout 500 
# Output: Error: 'timeout' value 500 is > maximum 300

Documentation

Requirements

License

Contributing