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Cocona

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

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# ![Cocona](https://raw.githubusercontent.com/mayuki/Cocona/master/docs/assets/logo.svg)
Micro-framework for .NET **Co**re **con**sole **a**pplication. Cocona makes it easy and fast to build console applications on .NET.🚀

[![Build Status](https://dev.azure.com/misuzilla/Cocona/_apis/build/status/Cocona?branchName=master)](https://dev.azure.com/misuzilla/Cocona/_build/latest?definitionId=18&branchName=master) [![NuGet Package: Cocona](https://img.shields.io/nuget/vpre/Cocona?label=NuGet%3A%20Cocona)](https://www.nuget.org/packages/Cocona) [![NuGet Package: Cocona.Lite](https://img.shields.io/nuget/vpre/Cocona.Lite?label=NuGet%3A%20Cocona.Lite)](https://www.nuget.org/packages/Cocona.Lite)

### ⏱ Create a console application with Cocona in seconds.
```csharp
CoconaApp.Run((string? name, bool hey) =>
    Console.WriteLine($"{(hey ? "Hey" :"Hello")} {(name ?? "Guest")}!"));
```
![](https://raw.githubusercontent.com/mayuki/Cocona/master/docs/assets/intro-in-seconds.gif)

## Feature
- 🚀 **Make it easy to build console applications on .NET.**
    - ASP.NET Core-like Minimal API
    - `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)](#performance--coconalite).

[You can find sample code for various features.](samples)

## Table of contents
- [Installing](#installing)
- [Requirements](#requirements)
- [Getting Started](#getting-started)
- [Command-line handling basics](#command-line-handling-basics)
    - [Command](#command)
    - [Options](#options)
    - [Arguments](#arguments)
    - [Sub-commands](#sub-commands)
    - [Option-like commands](#option-like-commands)
- [Cocona in action](#cocona-in-action)
    - [Parameter set](#parameter-set)
    - [Exit code](#exit-code)
    - [Validation](#validation)
    - [Shutdown event handling](#shutdown-event-handling)
    - [Command filter](#command-filter)
    - [Dependency Injection](#dependency-injection)
    - [Configuration](#configuration)
    - [Logging](#logging)
    - [Shell command-line completion](#shell-command-line-completion)
- [Performance & Cocona.Lite](#performance--coconalite)
- [Advanced](#advanced)
    - [Localization](#localization)
    - [Hide command from help](#hide-command-from-help)
    - [Help customization](#help-customization)
    - [CommandMethodForwardedTo attribute](#commandmethodforwardedto-attribute)
    - [IgnoreUnknownOptions attribute](#ignoreunknownoptions-attribute)
    - [GenericHost integration](#generichost-integration) 
- [Related projects](#related-projects)
- [License](#license)

## Installing
Install NuGet package from NuGet.org

```sh
$ dotnet add package Cocona

# A lightweight version is also available if you prefer less dependency.
$ dotnet add package Cocona.Lite
```

## Requirements
- .NET 6 (Required to use Minimal API)
- .NET 5
- .NET Standard 2.0, 2.1

## Getting Started

```csharp
using Cocona;
CoconaApp.Run((string name) =>
{
    Console.WriteLine($"Hello {name}");
})
```

<details><summary>Class-based style (for .NET Standard / .NET 5)</summary>

```csharp
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}");
    }
}
```
</details>

### Try to run!
```sh
$ 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](https://docs.microsoft.com/en-us/dotnet/core/whats-new/dotnet-core-3-0#single-file-executables))
```sh
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
#### Minimal API style

If your application has a single command, you can easily define and run it with `CoconaApp.Run`.

```csharp
CoconaApp.Run((string name, int age) => { ... });
```

This is equivalent to the following code using the Minimal API Builder.

```csharp
var builder = CoconaApp.CreateBuilder();
var app = builder.Build();

app.AddCommand((string name, int age) => { ... });

app.Run();
```

If you want your application to have more than one command, you can add named commands. See [Sub commands](#sub-commands) for details.

```csharp
var app = CoconaApp.Create(); // is a shorthand for `CoconaApp.CreateBuilder().Build()`

app.AddCommand("list", () => { ... });
app.AddCommand("add", () => { ... });
app.AddCommand("delete", () => { ... });

app.Run();
```

You can add (classic) Class-based style commands with the `AddCommands<T>` method.

```csharp
app.AddCommands<MyCommand>();
```

#### Public method as a command (Class-based style)
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](#sub-commands))

```csharp
// 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`.

```csharp
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).

```csharp
// This command accepts `--name <string>` and `--hey` options.
app.AddCommand((string name, bool hey) => { ... });
```

<details><summary>Class-based style (for .NET Standard / .NET 5)</summary>

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

If the parameter of a method is defined as nullable, Cocona will treat them as non-mandatory option for a command. (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.

```csharp
// `--name` is non-mandatory option.
// If the user runs the application without this option, the parameter will be `null`.
app.AddCommand((string? name) => { ... });
```

<details><summary>Optional with default value (Class-based style)</summary>

If method parameters are [optional argument](https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/named-and-optional-arguments#optional-arguments), 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.

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

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

```csharp
// 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
app.AddCommand(([Option('f')]bool force, [Option('r')]bool recursive) => { ... });
```

<details><summary>Class-based style (for .NET Standard / .NET 5))</summary>

```csharp
// 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) { ... }
```
</details>

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

```csharp
// $ 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" };
app.AddCommand(([Option('I')]string[] include, [Argument]string file) => { ... });
```

<details><summary>Class-based style (for .NET Standard / .NET 5))</summary>

```csharp
// $ 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) { ... }
```
</details>

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

```csharp
app.AddCommand((
    [Option(Description = "Description of the option")] int value,
    [Argument(Description = "Description of the argument")]string arg
) => { ... });
```

<details><summary>Class-based style (for .NET Standard / .NET 5))</summary>

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

```
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](samples/InAction.CommandOptions)

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

```csharp
// ./app alice karen
app.AddCommand(([Argument]string from, [Argument]string to) => { ... });
```
<details><summary>Class-based style (for .NET Standard / .NET 5)</summary>

```csharp
// ./app alice karen
public void Hello([Argument]string from, [Argument]string to) { ... }
```
</details>

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`).

```csharp
// ./copy file1 file2 file3 dest
app.AddCommand(([Argument]string[] src, [Argument]string dest) => { ... });
```

<details><summary>Class-based style (for .NET Standard / .NET 5)</summary>

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

- See also: [CoconaSample.InAction.ManyArguments](samples/InAction.ManyArguments)

### Sub-commands

You can add multiple commands with names and expose them as sub-commands. You can implement an application that has sub-commands similar to `dotnet`, `git`, `kubectl` etc...

```csharp
var app = CoconaApp.Create();
app.AddCommand("hello", ([Argument]string name) => Console.WriteLine($"Hello {name}!"))
    .WithDescription("Say hello");
app.AddCommand("bye", ([Argument]string name) => Console.WriteLine($"Goodbye {name}!"))
    .WithDescription("Say goodbye");
app.Run();
```

<details><summary>Class-based style (for .NET Standard / .NET 5)</summary>

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...

```csharp
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}!");
}
```
</details>

```bash
$ ./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.

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

Similar commands:
  hello
```

- See also: [CoconaSample.GettingStarted.SubCommandApp](samples/GettingStarted.SubCommandApp)

##### Nested sub-commands

Cocona also supports nested sub-commands. Specify the class that has nested sub-commands using `AddSubCommand` method.

```csharp
var app = CoconaApp.Create();
// ./myapp info
app.AddCommand("info", () => Console.WriteLine("Show information"));

// ./myapp server [command]
app.AddSubCommand("server", x =>
{
    x.AddCommand("start", () => Console.WriteLine("Start"));
    x.AddCommand("stop", () => Console.WriteLine("Stop"));
})
.WithDescription("Server commands");

// ./myapp client [command]
app.AddSubCommand("client", x =>
{
    x.AddCommand("connect", () => Console.WriteLine("Connect"));
    x.AddCommand("disconnect", () => Console.WriteLine("Disconnect"));
})
.WithDescription("Client commands");

app.Run();
```

<details><summary>Class-based style (for .NET Standard / .NET 5)</summary>

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

```csharp
[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");
}
```
</details>

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

SubCommandApp

Commands:
  start
  stop

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

#### PrimaryCommand
```csharp
var app = CoconaApp.Create();
app.AddCommand((bool foo, string bar) => { ... }); // Primary command

app.AddCommand("hello", () => { ... });
app.AddCommand("goodbye", () => { ... });
app.Run();
```

<details><summary>Class-based style (for .NET Standard / .NET 5)</summary>

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

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

[Command]
public void Goodbye() { ... }
```
</details>

### 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.

```csharp
var app = CoconaApp.Create();
app.AddCommand(() => Console.WriteLine("Execute"))
    .OptionLikeCommand(x =>
    {
        x.AddCommand("hello", ([Argument]string name) => Console.WriteLine($"Hello {name}!"))
            .WithAliases('f');
    });
app.Run();
```

<details><summary>Class-based style (for .NET Standard / .NET 5)</summary>

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

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

```bash
$ ./myapp
Execute

$ ./myapp --hello Alice
Hello Alice!
```

- See: [samples/Advanced.OptionLikeCommand](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

### Parameter set
Cocona has a mechanism called Parameter set that defines common parameters for multiple commands.
For example, if every command receives a user name, host name, etc., it would be annoying to define them in a method for each command.

A class or `record` implements the `ICommandParameterSet` interface and treats it as a Parameter set.

- See: [samples/InAction.ParameterSet](samples/InAction.ParameterSet)

#### By parameterized constructor (includes record class)
If a class (or record class) has a parameterized constructor, it is treated as part of the definition of a command method.

```csharp
public record CommonParameters(
    [Option('t', Description = "Specifies the remote host to connect.")]
    string Host,
    [Option('p', Description = "Port to connect to on the remote host.")]
    int Port,
    [Option('u', Description = "Specifies the user to log in as on the remote host.")]
    string User = "root",
    [Option('f', Description = "Perform without user confirmation.")]
    bool Force = false
) : ICommandParameterSet;

public void Add(CommonParameters commonParams, [Argument] string from, [Argument] string to)
    => Console.WriteLine($"Add: {commonParams.User}@{commonParams.Host}:{commonParams.Port} {(commonParams.Force ? " (Force)" : "")}");

public void Update(CommonParameters commonParams, [Option('r', Description = "Traverse recursively to perform.")] bool recursive, [Argument] string path)
    => Console.WriteLine($"Update: {commonParams.User}@{commonParams.Host}:{commonParams.Port} {(commonParams.Force ? " (Force)" : "")}");
```

#### By properties (parameter-less constructor)
If a class has a parameter-less constructor, you can mark the public property as `Option` or `Argument`.

**NOTE: Option defined as a property is treated as required by default. If you want a non-required Option to have a default value, mark it with `HasDefaultValue` attribute.**

```csharp
public class CommonParameters : ICommandParameterSet
{
    [Option('t', Description = "Specifies the remote host to connect.")]
    public string Host { get; set; }

[Option('p', Description = "Port to connect to on the remote host.")]
    public int Port { get; set; }

[Option('u', Description = "Specifies the user to log in as on the remote host.")]
    [HasDefaultValue]
    public string User  { get; set; } = "root";

[Option('f', Description = "Perform without user confirmation.")]
    public bool Force  { get; set; } = false;
}

### Exit code
```csharp
// 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](samples/InAction.ExitCode)

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

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

- `RangeAttribute`
- `MaxLengthAttribute`
- `MinLengthAttribute`
- ...

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

```csharp
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](samples/InAction.Validation)

### Shutdown event handling

```csharp
app.AddCommand(async (CoconaAppContext ctx) =>
{
    while (!ctx.CancellationToken.IsCancellationRequested)
    {
        await Task.Delay(100);
    }
});
```

<details><summary>Class-based style (for .NET Standard / .NET 5)</summary>

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

Alternatively, you can use `ICoconaAppContextAccessor` and `CoconaAppContext` to access `CancellationToken`.

```csharp
public async Task RunAsync([FromService]ICoconaAppContextAccessor contextAccessor)
{
    var ctx = contextAccessor.Current ?? throw new InvalidOperationException();
    while (!ctx.CancellationToken.IsCancellationRequested)
    {
        await Task.Delay(100);
    }
}
```
</details>

- See also: [CoconaSample.InAction.HandleShutdownSignal](samples/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

```csharp
var app = CoconaApp.Create();

// Add a command with command filters.
app.AddCommand(() =>
    {
        Console.WriteLine($"Hello Konnichiwa");
    })
    .WithFilter(new SampleCommandFilter())
    .WithFilter(async (ctx, next) =>
    {
        // You can declare and apply a filter using a delegate.
        return await next(ctx);
    });

// Add a command filter and apply it to commands after this call.
app.UseFilter(new MyFilter());

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}");
        }
    }
}
```

<details><summary>Class-based style (for .NET Standard / .NET 5)</summary>

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

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

- See also: [CoconaSample.InAction.CommandFilter](samples/InAction.CommandFilter)

### Dependency Injection
If a constructor has parameters, Cocona injects an instance obtained from IServiceProvider into the parameter.

```csharp
var builder = CoconaApp.CreateBuilder();
builder.Services.AddTransient<MyService>();

var app = builder.Build();
app.AddCommand((MyService myService) =>
{
    myService.Hello("Hello Konnichiwa!");
});
app.Run();

class MyService
{
    private readonly ILogger _logger;

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

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

<details><summary>Class-based style (for .NET Standard / .NET 5)</summary>

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]`.

```csharp
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);
    }
}
```
</details>

- See also: [CoconaSample.InAction.DependencyInjection](samples/InAction.DependencyInjection)

### Configuration
- See also: [CoconaSample.InAction.AppConfiguration](samples/InAction.AppConfiguration)

### Logging

```csharp
var builder = CoconaApp.CreateBuilder();
builder.Logging.AddDebug();

var app = builder.Build();

app.AddCommand((ILogger<Program> logger) => logger.LogInformation("Hello Konnichiwa!"));

app.Run();
```

<details><summary>Class-based style (for .NET Standard / .NET 5)</summary>

```csharp
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!");
    }
}
```
</details>

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

![Tab shell completion](https://user-images.githubusercontent.com/9012/83354785-effcd400-a395-11ea-8226-c21e114c746f.gif)

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.

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

Currently, The supported shells are `bash` and `zsh`.

This feature is **disabled** by default, or you can set the `EnableShellCompletionSupport` option to `true` if you 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](samples/Advanced.ShellCompletionCandidates)

## Performance & Cocona.Lite
`Microsoft.Extensions.*` are powerful but little heavy libraries. If you don't need`Microsoft.Extensions.*`, you can use a lightweight version of Cocona. (named [Cocona.Lite](https://www.nuget.org/packages/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`.

```sh
$ dotnet add package Cocona.Lite
```

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

```csharp
CoconaLiteApp.Run(() => { ... });
```

```csharp
var app = CoconaLiteApp.Create();
app.AddCommand(() => { ... });
app.Run();
```

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

## Advanced

### Localization
Microsoft.Extensions.Localization can be used to localize your application. Please refer to the sample code for details.

```csharp
// Register Microsoft.Extensions.Localization and ICoconaLocalizer services
// Cocona uses `ICoconaLocalizer` to localize command descriptions.
var builder = CoconaApp.CreateBuilder();
builder.Services.AddLocalization(options =>
{
    options.ResourcesPath = "Resources";
});

// `MicrosoftExtensionLocalizationCoconaLocalizer` is not included in Cocona core library.
builder.Services.TryAddTransient<ICoconaLocalizer, MicrosoftExtensionLocalizationCoconaLocalizer>();

var app = builder.Build();
app.AddCommand("hello", ([Argument(Description = "Name")]string name, IStringLocalizer<Program> localizer) =>
    {
        // Get a localized text from Microsoft.Extensions.Localization.IStringLocalizer (same as ASP.NET Core)
        Console.WriteLine(localizer.GetString("Hello {0}!", name));
    })
    .WithDescription("Say Hello");
app.Run();
```

- See also: [CoconaSample.Advanced.Localization](samples/Advanced.Localization)

### Hide command from help

```csharp
var app = CoconaApp.Create();
app.AddCommand("hello", (string name) =>
    {
        Console.WriteLine("Hello {0}!", name);
    });
app.AddCommand("secret-command", (string name) =>
    {
        Console.WriteLine("🙊");
    })
    .WithMetadata(new HiddenAttribute());
app.Run();
```

### Help customization
- See also: [CoconaSample.Advanced.HelpTransformer](samples/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.

```csharp
[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](samples/Advanced.CommandMethodForwarding)

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

### GenericHost integration

Cocona can be integrated with GenericHost of Microsoft.Extensions.Hosting.
You can register the services with `UseCocona` extension method.

```csharp
class Program
{
    static async Task Main(string[] args)
    {
        await Host.CreateDefaultBuilder()
            .ConfigureCocona(args, new[] { typeof(Program) })
            .Build()
            .RunAsync();
    }

public void Hello()
    {
        Console.WriteLine($"Hello Konnichiwa!");
    }
}
```

- See: [samples/Advanced.GenericHost](samples/Advanced.GenericHost)

## Related projects
- [Cysharp/ConsoleAppFramework](https://github.com/Cysharp/ConsoleAppFramework): ConsoleAppFramework heavily inspired Cocona.

Cocona

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