Go library to simplify CLI workflow
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README.md

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This is a simple Go library to manage commands for your CLI tool. Easy to use and now you can focus on Business Logic instead of building the command routing.

What this library does for you?

Manage your separated commands. How? Generates a general help and command specific helps for your commands. If your command fails somewhere (panic for example), commander will display the error message and the command specific help to guide your user.

Install

$ go get github.com/yitsushi/go-commander

Sample output (from totp-cli)

$ totp-cli help

change-password                   Change password
update                            Check and update totp-cli itself
version                           Print current version of this application
generate <namespace>.<account>    Generate a specific OTP
add-token [namespace] [account]   Add new token
list [namespace]                  List all available namespaces or accounts under a namespace
delete <namespace>[.account]      Delete an account or a whole namespace
help [command]                    Display this help or a command specific help

Usage

Every single command has to implement CommandHandler. Check this project for examples.

package main

// Import the package
import "github.com/yitsushi/go-commander"

// Your Command
type YourCommand struct {
}

// Executed only on command call
func (c *YourCommand) Execute(opts *commander.CommandHelper) {
  // Command Action
}

func NewYourCommand(appName string) *commander.CommandWrapper {
  return &commander.CommandWrapper{
    Handler: &YourCommand{},
    Help: &commander.CommandDescriptor{
      Name:             "your-command",
      ShortDescription: "This is my own command",
      LongDescription:  `This is a very long
description about this command.`,
      Arguments:        "<filename> [optional-argument]",
      Examples:         []string {
        "test.txt",
        "test.txt copy",
        "test.txt move",
      },
    },
  }
}

// Main Section
func main() {
	registry := commander.NewCommandRegistry()

	registry.Register(NewYourCommand)

	registry.Execute()
}

Now you have a CLI tool with two commands: help and your-command.

❯ go build mytool.go

❯ ./mytool
your-command <filename> [optional-argument]   This is my own command
help [command]                                Display this help or a command specific help

❯ ./mytool help your-command
Usage: mytool your-command <filename> [optional-argument]

This is a very long
description about this command.

Examples:
  mytool your-command test.txt
  mytool your-command test.txt copy
  mytool your-command test.txt move

How to use subcommand pattern?

When you create your main command, just create a new CommandRegistry inside the Execute function like you did in your main() and change Depth.

import subcommand "github.com/yitsushi/mypackage/command/something"

func (c *Something) Execute(opts *commander.CommandHelper) {
	registry := commander.NewCommandRegistry()
	registry.Depth = 1
	registry.Register(subcommand.NewSomethingMySubCommand)
	registry.Execute()
}

PreValidation

If you want to write a general pre-validation for your command or just simply keep your validation logic separated:

// Or you can define inline if you want
func MyValidator(c *commander.CommandHelper) {
  if c.Arg(0) == "" {
    panic("File?")
  }

  info, err := os.Stat(c.Arg(0))
  if err != nil {
    panic("File not found")
  }

  if !info.Mode().IsRegular() {
    panic("It's not a regular file")
  }

  if c.Arg(1) != "" {
    if c.Arg(1) != "copy" && c.Arg(1) != "move" {
      panic("Invalid operation")
    }
  }
}

func NewYourCommand(appName string) *commander.CommandWrapper {
  return &commander.CommandWrapper{
    Handler: &YourCommand{},
    Validator: MyValidator
    Help: &commander.CommandDescriptor{
      Name:             "your-command",
      ShortDescription: "This is my own command",
      LongDescription:  `This is a very long
description about this command.`,
      Arguments:        "<filename> [optional-argument]",
      Examples:         []string {
        "test.txt",
        "test.txt copy",
        "test.txt move",
      },
    },
  }
}

Define arguments with type

&commander.CommandWrapper{
  Handler: &MyCommand{},
  Arguments: []*commander.Argument{
    &commander.Argument{
      Name: "list",
      Type: "StringArray[]",
    },
  },
  Help: &commander.CommandDescriptor{
    Name: "my-command",
  },
}

In your command:

if opts.HasValidTypedOpt("list") == nil {
  myList := opts.TypedOpt("list").([]string)
  if len(myList) > 0 {
    mockPrintf("My list: %v\n", myList)
  }
}

Define own type

Yes you can ;)

// Define your struct (optional)
type MyCustomType struct {
	ID   uint64
	Name string
}

// register your own type with parsing/validation
commander.RegisterArgumentType("MyType", func(value string) (interface{}, error) {
  values := strings.Split(value, ":")

  if len(values) < 2 {
    return &MyCustomType{}, errors.New("Invalid format! MyType => 'ID:Name'")
  }

  id, err := strconv.ParseUint(values[0], 10, 64)
  if err != nil {
    return &MyCustomType{}, errors.New("Invalid format! MyType => 'ID:Name'")
  }

  return &MyCustomType{
      ID:   id,
      Name: values[1],
    },
    nil
})

// Define your command
&commander.CommandWrapper{
  Handler: &MyCommand{},
  Arguments: []*commander.Argument{
    &commander.Argument{
      Name:        "owner",
      Type:        "MyType",
      FailOnError: true,          // Optional boolean
    },
  },
  Help: &commander.CommandDescriptor{
    Name: "my-command",
  },
}

In yout command:

if opts.HasValidTypedOpt("owner") == nil {
  owner := opts.TypedOpt("owner").(*MyCustomType)
  mockPrintf("OwnerID: %d, Name: %s\n", owner.ID, owner.Name)
}