Micro-framework for .NET Core console application. Cocona makes it easy and fast to build console applications on .NET Core.🚀

⏱ Create a console application with Cocona in seconds.

Feature

• 🚀 Make it easy to build console applications on .NET Core.
  • public method as a command ™
  • Provides ASP.NET Core MVC-like development experience to console application development.
• ✨ Command-line option semantics like UNIX tools standard. (getopt/getopt_long like options)
  • Your app can handle both -rf / and -r -f / :-)
  • Support single command and multiple commands style
    • myapp --foo --bar -n arg0 "arg1" (e.g. dir, cp, ls ...)
    • myapp server -m "Hello world!" (e.g. dotnet, git, kubectl ...)
• ❓ Built-in help documentation support.
  • You want to see a help message; you type -h or --help.
  • Built-in similar commands suggestion
  • Shell command-line completion support for bash and zsh
• 🛠 Highly modulable/customizable CLI framework.
  • Cocona built on top of Microsoft.Extensions.* framework. Cocona natively supports Logging, DI, Configuration and ConsoleLifetime.
  • Don't you need Microsoft.Extensions.*? then you can use a lightweight version of Cocona (named Cocona.Lite).

You can find sample code for various features.

Table of contents

• Installing
• Getting Started
• Command-line handling basics
  • Command
  • Options
  • Arguments
  • Sub-commands
  • Option-like commands
• Cocona in action
  • Exit code
  • Validation
  • Shutdown event handling
  • Command filter
  • Dependency Injection
  • Configuration
  • Logging
  • Shell command-line completion
• Performance & Cocona.Lite
• Advanced
  • Help customization
  • CommandMethodForwardedTo attribute
  • IgnoreUnknownOptions attribute
• Related projects
• License

Installing

Install NuGet package from NuGet.org

$ dotnet add package Cocona

PS> Install-Package Cocona

Getting Started

using Cocona;
class Program
{
    static void Main(string[] args)
    {
        // Cocona parses command-line and executes a command.
        CoconaApp.Run<Program>(args);
    }

    // public method as a command ™
    public void Hello(string name)
    {
        Console.WriteLine($"Hello {name}");
    }
}

Try to run!

$ dotnet run
Usage: ConsoleAppSample [--name <String>]

Options:
  --name <String>    (Required)
  -h, --help         Show help message
  --version          Show version

$ dotnet run -- --name Cocona
Hello Cocona

Extra: Publish the application as a single-file executable

If your application runs on .NET Core 3.0 or later, you can publish the app as a single-file executable. (see. What's new in .NET Core 3.0)

PS> dotnet publish -r win-x64 -p:PublishSingleFile=true
PS> app.exe --name Cocona

$ dotnet publish -r linux-x64 -p:PublishSingleFile=true
$ ./app --name Cocona

Command-line handling basics

Command

Public method as a command ™

By default, Cocona treats public methods as commands.

If an application has one public method, Cocona calls it on startup. If there are more than one, they are treated as sub-commands. (see also Sub commands)

// Treats a method name as a command name. (Below method is named `command`)
public void Command() { ... }

// Specify a command name using CommandAttribute.
[Command("commandname")]
public void Command() { ... }

// Cocona will ignore this method.
[Ignore]
public void Ignored() { ... }

If you want to specify a method as a command manually, set false to TreatPublicMethodsAsCommands option at startup. All command methods require CommandAttribute.

CoconaApp.Run<Program>(args, options =>
{
    // If the option value is `false`, All command methods require `CommandAttribute`.
    options.TreatPublicMethodsAsCommands = false;
});

Options

Cocona exposes method parameters as command-line options (also known as flags).

// This command accepts `--name <string>` and `--hey` options.
public void Hello(string name, bool hey) { ... }

If method parameters are optional argument, Cocona treats those as optional command options. (That is, the parameters are treated as required option by default excepts boolean). If a parameter is boolean, it's assumed that false default value is specified.

// `--name "default user"` is specified implicity.
public void Hello(string name = "default user") { ... }

Do you want to use short-name option -f instead of --force? You can specify short-name to an option using OptionAttribute.

// The command accepts `-f` or `--force` option.
// Cocona's command-line parser accepts getopt-like styles. See below.
// $ remove --force --recursive
// $ remove -r -f
// $ remove -rf
public void Remove([Option('f')]bool force, [Option('r')]bool recursive) { ... }

If a parameter is T[] or IEnumerable<T>, a command accepts one or more options by the same name.

// $ compile -I../path/to/foo.h -I/usr/include/bar.h -I/usr/include/baz.h nantoka.c
// include = new [] { "../path/to/foo.h", "/usr/include/bar.h", "/usr/include/baz.h" };
public void Compile([Option('I')]string[] include, [Argument]string file) { ... }

You can also specify a description for options that appear in the help.

public void HasDescription([Option(Description = "Description of the option")] int value, [Argument(Description = "Description of the argument")]string arg) { ... }

Usage: CoconaSample.InAction.CommandOptions has-description [--value <Int32>] [--help] arg

Arguments:
  0: arg    Description of the argument (Required)

Options:
  --value <Int32>    Description of the option (Required)
  -h, --help         Show help message

• See also: CoconaSample.InAction.CommandOptions

Arguments

Command-line arguments are defined as method parameters as same as options.

// ./app alice karen
public void Hello([Argument]string from, [Argument]string to) { ... }

You can define a parameter as T[]. It allows defining cp-like command which accepts many file paths and one destination path (cp file1 file2 file3 dest).

// ./copy file1 file2 file3 dest
public void Copy([Argument]string[] src, [Argument]string dest) { ... }

• See also: CoconaSample.InAction.ManyArguments

Sub-commands

If a command type has more than one public method or [Command], those commands are exposed as sub-commands. You can implement an application that has sub-commands similar to dotnet, git, kubectl etc...

static void Main(string[] args)
{
    CoconaApp.Run<Program>(args);
}

[Command(Description = "Say hello")]
public void Hello([Argument]string name)
{
    Console.WriteLine($"Hello {name}!");
}

[Command(Description = "Say goodbye")]
public void Bye([Argument]string name)
{
    Console.WriteLine($"Goodbye {name}!");
}

$ ./SubCommandApp
Usage: SubCommandApp [command]
Usage: SubCommandApp [--help] [--version]

SubCommandApp

Commands:
  hello    Say hello
  bye      Say goodbye

Options:
  -h, --help    Show help message
  --version     Show version

When a user mistypes a command, Cocona prints command autogenerated suggestions.

$ ./SubCommandApp hell
Error: 'hell' is not a command. See '--help' for usage.

Similar commands:
  hello

• See also: CoconaSample.GettingStarted.SubCommandApp

Nested sub-commands

Cocona also supports nested sub-commands. Specify the class that has nested sub-commands using HasSubCommands attribute.

[HasSubCommands(typeof(Server), Description = "Server commands")]
[HasSubCommands(typeof(Client), Description = "Client commands")]
class Program
{
    static void Main(string[] args) => CoconaApp.Run<Program>(args);

    // ./myapp info
    public void Info() => Console.WriteLine("Show information");
}

// ./myapp server [command]
class Server
{
    public void Start() => Console.WriteLine("Start");
    public void Stop() => Console.WriteLine("Stop");
}

// ./myapp client [command]
class Client
{
    public void Connect() => Console.WriteLine("Connect");
    public void Disconnect() => Console.WriteLine("Disconnect");
}

$ ./SubCommandApp
Usage: SubCommandApp [command]
Usage: SubCommandApp [--help] [--version]

SubCommandApp

Commands:
  info
  server    Server commands
  client    Client commands

Options:
  -h, --help    Show help message
  --version     Show version

$ ./SubCommandApp
Usage: SubCommandApp server [command]
Usage: SubCommandApp server [--help]

SubCommandApp

Commands:
  start
  stop

Options:
  -h, --help    Show help message

PrimaryCommand

[PrimaryCommand]
public void Primary(bool foo, string bar) { ... }

[Command]
public void Hello() { ... }

[Command]
public void Goodbye() { ... }

Option-like commands

The option-like command is a way to achieve an independent command that at first glance, looks like an option in a command.

For example, easy to understand examples like --version and --help. These are the options of a command, but they behave as a command when specified.

[OptionLikeCommand("hello", new[] {'f'}, typeof(Program), nameof(Hello))]
public void Execute()
    => Console.WriteLine("Execute");

private void Hello([Argument]string name)
    => Console.WriteLine($"Hello {name}!");

$ ./myapp
Execute

$ ./myapp --hello Alice
Hello Alice!

• See: samples/Advanced.OptionLikeCommand

Limitations

• Any previous options or arguments specified by OptionLikeCommand will be ignored.
  • Example: If --foo --bar --optionlikecommand --baz arg0 and --optionlikecommand is an Option-like command, the command will be passed --baz arg0.
• Arguments are not displayed in help.

Cocona in action

Exit code

// Exit Code: 0
public void NoReturn() { }

// Exit Code: 123
public int Return() { return 123; }

// Exit Code: 255
public async Task<int> ReturnAsync() { return 255; }

// Exit Code: -1
public async ValueTask<int> ReturnValueTaskAsync() { return -1; }

// Exit Code: 128
public void Throw() { throw new CommandExitedException(128); }

• See also: CoconaSample.InAction.ExitCode

Validation

Cocona can use attributes to validate options and arguments. It is similar to ASP.NET Core MVC.

.NET Core (System.ComponentModel.DataAnnotations) has some pre-defined attributes:

• RangeAttribute
• MaxLangeAttribute
• MinLengthAttribute
• ...

If you want to implement custom validation attribute, it should inherit System.ComponentModel.DataAnnotations.ValidationAttribute attribute.

class Program
{
    static void Main(string[] args)
    {
        CoconaApp.Run<Program>(args);
    }

    public void Run([Range(1, 128)]int width, [Range(1, 128)]int height, [Argument][PathExists]string filePath)
    {
        Console.WriteLine($"Size: {width}x{height}");
        Console.WriteLine($"Path: {filePath}");
    }
}

class PathExistsAttribute : ValidationAttribute
{
    protected override ValidationResult IsValid(object value, ValidationContext validationContext)
    {
        if (value is string path && (Directory.Exists(path) || Directory.Exists(path)))
        {
            return ValidationResult.Success;
        }
        return new ValidationResult($"The path '{value}' is not found.");
    }
}

• See also: CoconaSample.InAction.Validation

Shutdown event handling

class Program : CoconaConsoleAppBase
{
    ...
    public async Task RunAsync()
    {
        while (!Context.CancellationToken.IsCancellationRequested)
        {
            await Task.Delay(100);
        }
    }
}

• See also: CoconaSample.InAction.HandleShutdownSignal

Command filter

Cocona has filter mechanism like ASP.NET Core's action filter. Filters allow custom processing before or after you run a command.

• ICommandFilter interface
• CommandFilterAttribute attribute
• IFilterProvider interface
• IFilterMetadata interface

class Program
{
    static void Main(string[] args)
    {
        CoconaApp.Run<Program>(args);
    }

    [SampleCommandFilter]
    public void Hello()
    {
        Console.WriteLine($"Hello Konnichiwa");
    }
}

class SampleCommandFilterAttribute : CommandFilterAttribute
{
    public override async ValueTask<int> OnCommandExecutionAsync(CoconaCommandExecutingContext ctx, CommandExecutionDelegate next)
    {
        Console.WriteLine($"Before Command: {ctx.Command.Name}");
        try
        {
            return await next(ctx);
        }
        finally
        {
            Console.WriteLine($"End Command: {ctx.Command.Name}");
        }
    }
}

• See also: CoconaSample.InAction.CommandFilter

Dependency Injection

If a constructor has parameters, Cocona injects an instance obtained from IServiceProvider into the parameter. Cocona will also inject an instance into the parameter if a command method parameter is marked as [FromService].

class Program
{
    public Program(ILogger<Program> logger)
    {
        logger.LogInformation("Create Instance");
    }

    static void Main(string[] args)
    {
        CoconaApp.Create()
            .ConfigureServices(services =>
            {
                services.AddTransient<MyService>();
            })
            .Run<Program>(args);
    }

    public void Hello([FromService]MyService myService)
    {
        myService.Hello("Hello Konnichiwa!");
    }
}

class MyService
{
    private readonly ILogger _logger;

    public MyService(ILogger<MyService> logger)
    {
        _logger = logger;
    }

    public void Hello(string message)
    {
        _logger.LogInformation(message);
    }
}

• See also: CoconaSample.InAction.DependencyInjection

Configuration

• See also: CoconaSample.InAction.AppConfiguration

Logging

class Program : CoconaConsoleAppBase
{
    static void Main(string[] args)
    {
        CoconaApp.Create()
            .ConfigureLogging(logging =>
            {
                logging.AddDebug();
            })
            .Run<Program>(args);
    }

    public async Task RunAsync()
    {
        Context.Logger.LogInformation("Hello Konnichiwa!");
    }
}

Shell command-line completion

Cocona provides support for shell command-line completion (also known as tab completion).

Cocona generates a shell script for command-line completion from a command definition and allows users to use command-line completion by loading it. The --completion built-in option is used to specify the name of a shell to generate a script.

$ source <(./myapp --completion bash)
or
% ./myapp --completion zsh > ~/.zsh/functions

Currently, The supported shells are bash and zsh.

This feature is enabled by default, or you can set the EnableShellCompletionSupport option to false if you don't need it.

It is also possible to dynamically generate command-line completion candidates and to prepare candidates at script generation time. Please see the sample below for more details.

• See: samples/Advanced.ShellCompletionCandidates

Performance & Cocona.Lite

Microsoft.Extensions.* are powerful but little heavy libraries. If you don't needMicrosoft.Extensions.*, you can use a lightweight version of Cocona. (named Cocona.Lite)

Feature & Limitation

• Almost the same features and APIs as Cocona (command-line, help, etc.)
• No Microsoft.Extensions.* dependencies
  • No Logging, DI, Configuration are provided
• Fewer overheads
• The minimal Dependency Injection function

Installing & How to use

Just install NuGet package Cocona.Lite instead of Cocona.

$ dotnet add package Cocona.Lite

Then in your source code, use CoconaLiteApp class instead of CoconaApp class.

static void Main(string[] args)
{
    CoconaLiteApp.Run<Program>(args);
}

Benchmark

BenchmarkDotNet=v0.12.0, OS=Windows 10.0.18363
Intel Core i7-8650U CPU 1.90GHz (Kaby Lake R), 1 CPU, 8 logical and 4 physical cores
.NET Core SDK=3.1.101
  [Host]     : .NET Core 3.1.1 (CoreCLR 4.700.19.60701, CoreFX 4.700.19.60801), X64 RyuJIT
  DefaultJob : .NET Core 3.1.1 (CoreCLR 4.700.19.60701, CoreFX 4.700.19.60801), X64 RyuJIT

• See also Tyrrz/Clifx#benchmark

Advanced

Help customization

• See also: CoconaSample.Advanced.HelpTransformer

CommandMethodForwardedTo attribute

The CommandMethodForwardedTo attribute allows you to specify that the substance of the specified command method is a different method and that the operation should be forwarded. If this attribute is given to a command method, the destination's attribute and its implementation are used. Excepts for the Command and Hidden attributes specified by the method.

For example, it can be used if the command implementation is defined in an external assembly or to call a built-in command (such as help) or compatibility purposes.

[CommandMethodForwardedTo(typeof(BuiltInOptionLikeCommands), nameof(BuiltInOptionLikeCommands.ShowHelp))]
public void MyHelp()
    => throw new NotSupportedException(); // NOTE: The method body and parameters used is BuiltInOptionLikeCommands.ShowHelp.

• See: samples/Advanced.CommandMethodForwarding

IgnoreUnknownOptions attribute

Cocona treats unknown options as errors by default. Now, you can set the IgnoreUnknownOptions attribute to ignore unknown options.

Related projects

• Cysharp/ConsoleAppFramework: ConsoleAppFramework heavily inspired Cocona.

License

MIT License

Copyright © 2020-present Mayuki Sawatari <[email protected]>