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Commander is a Swift framework for decoding command-line arguments by integrating with Swift standard library protocols Decodable & Decoder. Commander can help you to write structured cli program by declaring the structure of command and options of that command without writing any codes to parse the cli arguments. With Commander, you just need to focus on writing options structure of commands, the rest works will be handled by Commander automatically.

Table Of Contents

Features - Example

Features

  • Structured-CLI, commands and options are all structured by declaration of struct or class.
  • Options types are type-safe by implementing Decodable protocol.
  • Automatically generate help message for the commander or command.
  • Shell <Tab> completion supported. Bash/Zsh <Tab> auto-complete scripts supported.
  • Swift 4.x compatibility.
  • Zero dependency and pure Swift.
  • Supports Linux with swift build.

Example

With Commander, a command and its associated options could be defined as follows:

import Commander

public struct SampleCommand: CommandRepresentable {
  public struct Options: OptionsRepresentable {
    public typealias ArgumentsResolver = AnyArgumentsResolver<String>
    public enum CodingKeys: String, CodingKeysRepresentable {
      case verbose = "verbose"
      case stringValue = "string-value"
    }

    public static let keys: [Options.CodingKeys : Character] = [
      .verbose: "v",
      .stringValue: "s"
    ]

    public static let descriptions: [Options.CodingKeys : OptionDescription] = [
      .verbose: .usage("Prints the logs of the command"),
      .stringValue: .usage("Pass a value of String to the command")
    ]

    public var verbose: Bool = false
    public var stringValue: String = ""
  }

  public static let symbol: String = "sample"
  public static let usage: String = "Show sample usage of commander"

  public static func main(_ options: Options) throws {
    print(options)
    print("arguments: \(options.arguments)")
    print("\n\n\(Options.CodingKeys.stringValue.stringValue)")
  }
}

Then, configuring the available commands would like this:

import Commander

Commander.commands = [
  SampleCommand.self,
  NoArgsCommand.self
]
Commander.usage = "The sample usage command of 'Commander'"
Commander().dispatch() // Call this to dispatch and run the command

After which, arguments can be resolved by declaration of ArgumentsResolver:

public typealias ArgumentsResolver = AnyArgumentsResolver<T> // T must be Decodable

And you can fetch the arguments by:

public static func main(_ options: Options) throws {
  print("arguments: \(options.arguments)") // 'arguments' is being declared in OptionsRepresentable 
}

At last, run from shell:

commander-sample sample --verbose --string-value String arg1 arg2
# 
# Options(verbose: true, stringValue: "String")
# arguments: ["arg1", "arg2"]
#
#
# string-value

It's easy and fun!!!

Requirements - Test Coverage Graph - Installation

Requirements

  • Mac OS X 10.10+ / Ubuntu 14.10
  • Xcode 10
  • Swift 4.2

Test Coverage Graph

Installation

With SPM

// swift-tools-version:4.2
dependencies: [
  .package(url: "https://github.com/devedbox/Commander.git", "0.5.6..<100.0.0")
]

Patterns - Value Types

Patterns

Key-Value Pairs

Single Value

commander command --key value --key1=value1
commander command --bool
commander command -k value -K=value1
commander command -z=value # {"z": "value"}
commander command -z # {"z": true}
commander command -zop # {"z": true, "o": true, "p": true}

Multiple Values

commander command --array val1,val2,val3
commander command -a val1,val2,val3
commander command --dict key1=val1,key2=val2,key3=val3
commander command -d key1=val1,key2=val2,key3=val3
commander command --array val1 --array val2 --array val3
commander command -a val1 -a val2 -a val3
commander command --dict key1=val1 --dict key2=val2 --dict key3=val3
commander command -d key1=val1 -d key2=val2 -d key3=val3

Argument

In Commander，The position of arguments is not settled, they can be arywhere but the arguments must be continuous:

commander command args... --options                   # before options
commander command --options args...                   # after options
commander command --options args... --options         # between options
commander command arg0... --options arg1... --options # Error

Use -- to mark the ends of options and begins of arguments, but, this is normally optional in Commander:

commander command --options -- args...

Value Types

As we all know, all the arguments from CommandLine.arguments is String type, in Commander, the available value types are:

  • Bool: commander command --verbose
  • Int(8, 16, 32, 64...): commander command --int 100
  • String: commander command --string "this is a string value"
  • Array: commander command --array val1,val2,val3
  • Dictionary: commander command --dict key1=val1,key2=val2,key3=val3

Array object is delimited by character , and Dict object is delimited by character = and ,.

Advanced Usage - License

Usage

Commander supports a main commander alongwith the commands of that commander, and each command has its own subcommands and options.

Using a Commander is simple, you just need to declare the commands, usage of the commander, and then call Commander().dispatch(), the Commander will automatically decode the command line arguments and dispatch the decoded options to the specific command given by command line.

Just as simple as following:

import Commander

Commander.commands = [
  SampleCommand.self,
  NoArgsCommand.self
]
Commander.usage = "The sample usage command of 'Commander'"
Commander().dispatch()

Command

In Commander, a command is a type(class or struct) that conforms to protocol CommandRepresentable. The protocol CommandRepresentable declares the infos of the conforming commands:

  • Options: The associated type of command's options.
  • symbol: The symbol of the command used by command line shell.
  • usage: The usage help message for that command.
  • children: The subcommands of that command.

Creating A Command

public struct Hello: CommandRepresentable {
  public struct Options: OptionsRepresentable {
    public enum CodingKeys: String, CodingKeysRepresentable {
      case verbose
    }
    
    public static let descriptions: [SampleCommand.Options.CodingKeys : OptionDescription] = [
      .verbose: .usage("Prints the logs of the command"),
    ]
    
    public var verbose: Bool = false
  }
  
  public static let symbol: String = "sample"
  public static let usage: String = "Show sample usage of commander"
  
  public static func main(_ options: Options) throws {
    if options.verbose {
      print(options.argiments.first ?? "")
    }
  }
}

Dispatching A Command

Once a command has been created, it can be dispathed against a list of arguments, usually taken from CommandLine.arguments with dropping of the symbol of command itself.

let arguments = ["sample", "--verbose", "Hello world"]
Command.dispatch(with: arguments.dropFirst())
// Hello world

As a real dispatching of command, you don't need to dispatch the command manually, the dispatching will be handled by Commander automatically.

Adding Subcommands

Adding subcommands in Commander is by declaring the children of type [CommandDescribable.Type]:

public struct Hello: CommandRepresentable {
  ...
  public static let children: [CommandDescribable.Type] = [
    Subcommand1.self,
    Subcommand2.self
  ]
  ...
}

Options

The Options is the same as command, is a type(class or struct) that conforms to protocol OptionsRepresentable which inherited from Decodable and can be treated as a simple data model, will be decoed by the built in code type OptionsDecoder in Commander.

Declaring An Options

As mentioned earlier in Creating a Command, declaring an options type is extremely easy, just another data model represents the raw string in command line arguments:

public struct Options: OptionsRepresentable {
  public enum CodingKeys: String, CodingKeysRepresentable {
    case verbose
  }

  public static let descriptions: [SampleCommand.Options.CodingKeys : OptionDescription] = [
    .verbose: .usage("Prints the logs of the command"),
  ]

  public var verbose: Bool = false
}

Changing Option Symbol

As declared as public var verbose: Bool, we can use symbol in command line with --verbose accordingly, but how to use another different symbol in command line to wrap verbose such as --is-verbose? In Commander, we can just do as this:

public enum CodingKeys: String, CodingKeysRepresentable {
  case verbose = "is-verbose"
}

Providing A Short Key

Sometimes in develping command line tools, using a pattern like -v is necessary and helpful. In Commander, providing a short key for option is easy, we just need to declare a key-value pairs of type [CodingKeys: Character] in Options.keys:

public struct Options: OptionsRepresentable {
  ...
  public static let keys: [CodingKeys: Character] = [
    .verbose: "v"
  ]
  ...
}

Providing A Default Value

When we difine a flag option in our command, provide a default value for flag is required because if we miss typing the flag in command line, the value of that flag means false. Providing default value in Commander is by add declaration in Options.descritions as this:

public struct Options: OptionsRepresentable {
  ...
  public static let descriptions: [SampleCommand.Options.CodingKeys : OptionDescription] = [
    .verbose: .default(value: false, usage:"Prints the logs of the command")
  ]
  ...
}

Help Menu

In Commander, help menu is generated by CommandDescriber describing types conforming CommandDescribable automatically, including commander itself and all declared commands.

To provide help menu usages, in commands:

public struct Hello: CommandRepresentable {
  ...
  public static let symbol: String = "sample"
  public static let usage: String = "Show sample usage of commander"
  ...
}

In options:

public struct Options: OptionsRepresentable {
  ...
  public static let descriptions: [SampleCommand.Options.CodingKeys : OptionDescription] = [
    .verbose: .default(value: false, usage:"Prints the logs of the command")
  ]
  ...
}

Normally, the help usage message and default can both be provided by type OptionsDescriotion.

After declaration of usages, run help in terminal:

commander-sample --help # or, commander-sample help
# Usage:
#
#   $ commander-sample [COMMAND] [OPTIONS]
#
#     The sample usage command of 'Commander'
#
#   Commands:
#
#     help        Prints the help message of the command. Usage: [help [COMMANDS]]
#     sample      Show sample usage of commander
#     set-args    Set arguments of the command with given arguments
#
#   Options:
#
#     -h, --help  Prints the help message of the command. Usage: [[--help|-h][COMMAND --help][COMMAND -h]]

For specific commands, run as this:

commander-sample help sample # or, commander-sample sample --help
# Usage of 'sample':
#
#   $ commander-sample sample [SUBCOMMAND] [OPTIONS] [ARGUMENTS]
#
#     Show sample usage of commander
#
#   Subcommands:
#
#     set-args            Set arguments of the command with given arguments
#
#   Options:
#
#     -s, --string-value  Pass a value of String to the command
#     -h, --help          Prints the help message of the command. Usage: [[--help|-h][COMMAND --help][COMMAND -h]]
#     -v, --verbose       Prints the logs of the command
#
#   Arguments:
#
#     [String]            commander-sample sample [options] arg1 arg2 ...

Arguments

In Commander, an option can take multiple arguments from command line arguments as the arguments of that option, and can be accessed by calling options.arguments. The arguments decoding can not be resolvable by default, if you want to resolve the decoding of arguments, you must declare the ArgumentsResolver of the options:

public struct Options: OptionsRepresentable {
  ...
  public typealias ArgumentsResolver = AnyArgumentsResolver<String>
  ...
}

The type AnyArgumentsResolver<T> is generic type where the type T representing the type of arguments' element. With the declaration above, we can do this is command line:

commander hello --verbose -- "Hello world" "Will be dropped"
# "Hello world" "Will be dropped" are both the arguments of Hello.Options

Completions

Commander provided the api to write auto-completion in bash/zsh, the requirement is declared in protocol ShellCompletable. The CommandDescribable and OptionsDescribable is inherited from ShellCompletable by default.

To implemente auto-completion, you just need to write:

import Commander.Utility
// Options:
public static func completions(for commandLine: Utility.CommandLine) -> [String] {
  switch key {
  case "--string-value":
    return [
      "a", "b", "c"
    ]
  default:
    return [ ]
  }
}

In terminal, type this:

commander sample --string-value <Tab>
# a	b	c

Installing Completion Scripts

Commander can generate auto-completion scripts for you, you can run the built-in command complete generate to generate the scripts according to the shell type. Currently available shells are:

  • bash
  • zsh

Bash

  • run in terminal：commander complete generate --shell=bash > ./bash_completion
  • then：source ./bash_completion
  • or, install the scripts to the login scripts of bash for good at ~/.profile

Zsh

  • run in terminal：commander complete generate --shell=zsh > ~/zsh_completions/_commander
  • add contents to ~/.zshrc: 
    fpath=(~/zsh_completions $fpath)
autoload -U +X compinit && compinit
autoload -U +X bashcompinit && bashcompinit
  • restart you terminal

Write Your Own Completion

CommandDescribable already provided the default implementation of completion, by default, CommandDescribable provides the subcommands alongwith options as the completions for shell, you can override the default implementation to provide your custom completions to Commander.

OptionsDescribable returns an empty completions by default, OptionsDescribable will be called during the calling of CommandDescribable automatically, You must override the implementation of OptionsDescribable to provide your completions or an empty completions will be used.

This is an example to provide git branchs completions to shell:

import Commander.Utility

public static func completions(for commandLine: Utility.CommandLine) -> [String] {
  let current = commandLine.arguments.last
  let previous = commandLine.arguments.dropLast().last

  switch current {
  default:
    let outputs = ShellIn("git branch -r").execute().output.flatMap {
      String(data: $0, encoding: .utf8)
    } ?? ""

    return outputs.split(whereSeparator: {
      " *->\n".contains($0)
    }).map {
      if $0.hasPrefix("origin/") {
        return String(String($0)["origin/".endIndex...])
      } else {
        return String($0)
      }
    }
  }
}

License

Commander is released under the MIT license.