Update version

CliFx.Benchmarks/Commands/CliFxCommand.cs

@@ -17,6 +17,6 @@ namespace CliFx.Benchmarks.Commands
         [CommandOption("bool", 'b')]
         public bool BoolOption { get; set; }
 
-        public Task ExecuteAsync(IConsole console, CancellationToken cancellationToken) => Task.CompletedTask;
+        public Task ExecuteAsync(IConsole console) => Task.CompletedTask;
     }
 }

CliFx.Demo/Commands/BookAddCommand.cs

@@ -32,7 +32,7 @@ namespace CliFx.Demo.Commands
             _libraryService = libraryService;
         }
 
-        public Task ExecuteAsync(IConsole console, CancellationToken cancellationToken)
+        public Task ExecuteAsync(IConsole console)
         {
             // To make the demo simpler, we will just generate random publish date and ISBN if they were not set
             if (Published == default)

CliFx.Demo/Commands/BookCommand.cs

@@ -21,7 +21,7 @@ namespace CliFx.Demo.Commands
             _libraryService = libraryService;
         }
 
-        public Task ExecuteAsync(IConsole console, CancellationToken cancellationToken)
+        public Task ExecuteAsync(IConsole console)
         {
             var book = _libraryService.GetBook(Title);
 

CliFx.Demo/Commands/BookListCommand.cs

@@ -17,7 +17,7 @@ namespace CliFx.Demo.Commands
             _libraryService = libraryService;
         }
 
-        public Task ExecuteAsync(IConsole console, CancellationToken cancellationToken)
+        public Task ExecuteAsync(IConsole console)
         {
             var library = _libraryService.GetLibrary();
 

CliFx.Demo/Commands/BookRemoveCommand.cs

@@ -20,7 +20,7 @@ namespace CliFx.Demo.Commands
             _libraryService = libraryService;
         }
 
-        public Task ExecuteAsync(IConsole console, CancellationToken cancellationToken)
+        public Task ExecuteAsync(IConsole console)
         {
             var book = _libraryService.GetBook(Title);
 

CliFx.Tests/CliApplicationTests.cs

@@ -3,6 +3,7 @@ using NUnit.Framework;
 using System;
 using System.Collections.Generic;
 using System.IO;
+using System.Threading;
 using System.Threading.Tasks;
 using CliFx.Services;
 using CliFx.Tests.Stubs;
@@ -237,8 +238,9 @@ namespace CliFx.Tests
         {
             // Arrange
             using (var stdoutStream = new StringWriter())
+            using (var cancellationTokenSource = new CancellationTokenSource())
             {
-                var console = new VirtualConsole(stdoutStream);
+                var console = new VirtualConsole(stdoutStream, cancellationTokenSource.Token);
                 
                 var application = new CliApplicationBuilder()
                     .AddCommand(typeof(CancellableCommand))
@@ -248,7 +250,7 @@ namespace CliFx.Tests
 
                 // Act
                 var runTask = application.RunAsync(args);
-                console.Cancel();
+                cancellationTokenSource.Cancel();
                 var exitCode = await runTask.ConfigureAwait(false);
                 var stdOut = stdoutStream.ToString().Trim();
 

CliFx.Tests/TestCommands/CancellableCommand.cs

@@ -1,5 +1,4 @@
 using System;
-using System.Threading;
 using System.Threading.Tasks;
 using CliFx.Attributes;
 using CliFx.Services;
@@ -9,13 +8,13 @@ namespace CliFx.Tests.TestCommands
     [Command("cancel")]
     public class CancellableCommand : ICommand
     {
-        public async Task ExecuteAsync(IConsole console, CancellationToken cancellationToken)
+        public async Task ExecuteAsync(IConsole console)
         {
             await Task.Yield();
 
             console.Output.WriteLine("Printed");
 
-            await Task.Delay(TimeSpan.FromSeconds(1), cancellationToken).ConfigureAwait(false);
+            await Task.Delay(TimeSpan.FromSeconds(1), console.GetCancellationToken()).ConfigureAwait(false);
 
             console.Output.WriteLine("Never printed");
         }

CliFx.Tests/TestCommands/CommandExceptionCommand.cs

@@ -15,6 +15,6 @@ namespace CliFx.Tests.TestCommands
         [CommandOption("msg", 'm')]
         public string Message { get; set; }
         
-        public Task ExecuteAsync(IConsole console, CancellationToken cancellationToken) => throw new CommandException(Message, ExitCode);
+        public Task ExecuteAsync(IConsole console) => throw new CommandException(Message, ExitCode);
     }
 }

CliFx.Tests/TestCommands/ConcatCommand.cs

@@ -15,7 +15,7 @@ namespace CliFx.Tests.TestCommands
         [CommandOption('s', Description = "String separator.")]
         public string Separator { get; set; } = ""; 
         
-        public Task ExecuteAsync(IConsole console, CancellationToken cancellationToken)
+        public Task ExecuteAsync(IConsole console)
         {
             console.Output.WriteLine(string.Join(Separator, Inputs));
             return Task.CompletedTask;

CliFx.Tests/TestCommands/DivideCommand.cs

@@ -17,7 +17,7 @@ namespace CliFx.Tests.TestCommands
         // This property should be ignored by resolver
         public bool NotAnOption { get; set; }
         
-        public Task ExecuteAsync(IConsole console, CancellationToken cancellationToken)
+        public Task ExecuteAsync(IConsole console)
         {
             console.Output.WriteLine(Dividend / Divisor);
             return Task.CompletedTask;

CliFx.Tests/TestCommands/DuplicateOptionNamesCommand.cs

@@ -14,6 +14,6 @@ namespace CliFx.Tests.TestCommands
         [CommandOption("fruits")]
         public string Oranges { get; set; }
         
-        public Task ExecuteAsync(IConsole console, CancellationToken cancellationToken) => Task.CompletedTask;
+        public Task ExecuteAsync(IConsole console) => Task.CompletedTask;
     }
 }

CliFx.Tests/TestCommands/DuplicateOptionShortNamesCommand.cs

@@ -14,6 +14,6 @@ namespace CliFx.Tests.TestCommands
         [CommandOption('f')]
         public string Oranges { get; set; }
         
-        public Task ExecuteAsync(IConsole console, CancellationToken cancellationToken) => Task.CompletedTask;
+        public Task ExecuteAsync(IConsole console) => Task.CompletedTask;
     }
 }

CliFx.Tests/TestCommands/EnvironmentVariableCommand.cs

@@ -11,6 +11,6 @@ namespace CliFx.Tests.TestCommands
 		[CommandOption("opt", EnvironmentVariableName = "ENV_SINGLE_VALUE")]
 		public string Option { get; set; }
 
-		public Task ExecuteAsync(IConsole console, CancellationToken cancellationToken) => Task.CompletedTask;
+		public Task ExecuteAsync(IConsole console) => Task.CompletedTask;
 	}
 }

CliFx.Tests/TestCommands/EnvironmentVariableWithMultipleValuesCommand.cs

@@ -12,6 +12,6 @@ namespace CliFx.Tests.TestCommands
 		[CommandOption("opt", EnvironmentVariableName = "ENV_MULTIPLE_VALUES")]
 		public IEnumerable<string> Option { get; set; }
 
-		public Task ExecuteAsync(IConsole console, CancellationToken cancellationToken) => Task.CompletedTask;
+		public Task ExecuteAsync(IConsole console) => Task.CompletedTask;
 	}
 }

CliFx.Tests/TestCommands/EnvironmentVariableWithoutCollectionPropertyCommand.cs

@@ -12,6 +12,6 @@ namespace CliFx.Tests.TestCommands
         [CommandOption("opt", EnvironmentVariableName = "ENV_MULTIPLE_VALUES")]
         public string Option { get; set; }
 
-        public Task ExecuteAsync(IConsole console, CancellationToken cancellationToken) => Task.CompletedTask;
+        public Task ExecuteAsync(IConsole console) => Task.CompletedTask;
     }
 }

CliFx.Tests/TestCommands/ExceptionCommand.cs

@@ -12,6 +12,6 @@ namespace CliFx.Tests.TestCommands
         [CommandOption("msg", 'm')]
         public string Message { get; set; }
         
-        public Task ExecuteAsync(IConsole console, CancellationToken cancellationToken) => throw new Exception(Message);
+        public Task ExecuteAsync(IConsole console) => throw new Exception(Message);
     }
 }

CliFx.Tests/TestCommands/HelloWorldDefaultCommand.cs

@@ -8,7 +8,7 @@ namespace CliFx.Tests.TestCommands
     [Command]
     public class HelloWorldDefaultCommand : ICommand
     {
-        public Task ExecuteAsync(IConsole console, CancellationToken cancellationToken)
+        public Task ExecuteAsync(IConsole console)
         {
             console.Output.WriteLine("Hello world.");
             return Task.CompletedTask;

CliFx.Tests/TestCommands/HelpDefaultCommand.cs

@@ -14,6 +14,6 @@ namespace CliFx.Tests.TestCommands
         [CommandOption("option-b", 'b', Description = "OptionB description.")]
         public string OptionB { get; set; }
 
-        public Task ExecuteAsync(IConsole console, CancellationToken cancellationToken) => Task.CompletedTask;
+        public Task ExecuteAsync(IConsole console) => Task.CompletedTask;
     }
 }

CliFx.Tests/TestCommands/HelpNamedCommand.cs

@@ -14,6 +14,6 @@ namespace CliFx.Tests.TestCommands
         [CommandOption("option-d", 'd', Description = "OptionD description.")]
         public string OptionD { get; set; }
 
-        public Task ExecuteAsync(IConsole console, CancellationToken cancellationToken) => Task.CompletedTask;
+        public Task ExecuteAsync(IConsole console) => Task.CompletedTask;
     }
 }

CliFx.Tests/TestCommands/HelpSubCommand.cs

@@ -11,6 +11,6 @@ namespace CliFx.Tests.TestCommands
         [CommandOption("option-e", 'e', Description = "OptionE description.")]
         public string OptionE { get; set; }
 
-        public Task ExecuteAsync(IConsole console, CancellationToken cancellationToken) => Task.CompletedTask;
+        public Task ExecuteAsync(IConsole console) => Task.CompletedTask;
     }
 }

CliFx.Tests/TestCommands/NonAnnotatedCommand.cs

@@ -6,6 +6,6 @@ namespace CliFx.Tests.TestCommands
 {
     public class NonAnnotatedCommand : ICommand
     {
-        public Task ExecuteAsync(IConsole console, CancellationToken cancellationToken) => Task.CompletedTask;
+        public Task ExecuteAsync(IConsole console) => Task.CompletedTask;
     }
 }

CliFx/CliApplication.cs

@@ -171,7 +171,7 @@ namespace CliFx
             _commandInitializer.InitializeCommand(command, targetCommandSchema, commandInput);
 
             // Execute command
-            await command.ExecuteAsync(_console, _console.CancellationToken);
+            await command.ExecuteAsync(_console);
 
             // Finish the chain with exit code 0
             return 0;

CliFx/CliFx.csproj

@@ -2,7 +2,7 @@
 
   <PropertyGroup>
     <TargetFrameworks>net45;netstandard2.0</TargetFrameworks>
-    <Version>0.0.6</Version>
+    <Version>0.0.7</Version>
     <Company>Tyrrrz</Company>
     <Authors>$(Company)</Authors>
     <Copyright>Copyright (C) Alexey Golub</Copyright>

CliFx/ICommand.cs

@@ -13,6 +13,6 @@ namespace CliFx
         /// Executes command using specified implementation of <see cref="IConsole"/>.
         /// This method is called when the command is invoked by a user through command line interface.
         /// </summary>
-        Task ExecuteAsync(IConsole console, CancellationToken cancellationToken);
+        Task ExecuteAsync(IConsole console);
     }
 }

CliFx/Services/IConsole.cs

@@ -55,8 +55,9 @@ namespace CliFx.Services
         void ResetColor();
 
         /// <summary>
-        /// Cancels when soft cancellation requested.
+        /// Provides token that cancels when application cancellation is requested.
+        /// Subsequent calls return the same token.
         /// </summary>
-        CancellationToken CancellationToken { get; }
+        CancellationToken GetCancellationToken();
     }
 }

CliFx/Services/SystemConsole.cs

@@ -9,21 +9,7 @@ namespace CliFx.Services
     /// </summary>
     public class SystemConsole : IConsole
     {
-        private readonly CancellationTokenSource _cancellationTokenSource = new CancellationTokenSource();
-
-        /// <inheritdoc />
-        public SystemConsole()
-        {
-            // Subscribe to CancelKeyPress event with cancellation token source
-            // Kills app on second cancellation (hard cancellation)
-            Console.CancelKeyPress += (_, args) =>
-            {
-                if (_cancellationTokenSource.IsCancellationRequested) 
-                    return;
-                args.Cancel = true;
-                _cancellationTokenSource.Cancel();
-            };
-        }
+        private CancellationTokenSource _cancellationTokenSource;
         
         /// <inheritdoc />
         public TextReader Input => Console.In;
@@ -61,6 +47,24 @@ namespace CliFx.Services
         public void ResetColor() => Console.ResetColor();
 
         /// <inheritdoc />
-        public CancellationToken CancellationToken => _cancellationTokenSource.Token;
+        public CancellationToken GetCancellationToken()
+        {
+            if (_cancellationTokenSource is null)
+            {
+                _cancellationTokenSource = new CancellationTokenSource();
+
+                // Subscribe to CancelKeyPress event with cancellation token source
+                // Kills app on second cancellation (hard cancellation)
+                Console.CancelKeyPress += (_, args) =>
+                {
+                    if (_cancellationTokenSource.IsCancellationRequested)
+                        return;
+                    args.Cancel = true;
+                    _cancellationTokenSource.Cancel();
+                };
+            }
+
+            return _cancellationTokenSource.Token;
+        }
     }
 }

CliFx/Services/VirtualConsole.cs

@@ -12,7 +12,7 @@ namespace CliFx.Services
     /// </summary>
     public class VirtualConsole : IConsole
     {
-        private readonly CancellationTokenSource _cancellationTokenSource = new CancellationTokenSource();
+        private readonly CancellationToken _cancellationToken;
 
         /// <inheritdoc />
         public TextReader Input { get; }
@@ -43,7 +43,8 @@ namespace CliFx.Services
         /// </summary>
         public VirtualConsole(TextReader input, bool isInputRedirected,
             TextWriter output, bool isOutputRedirected,
-            TextWriter error, bool isErrorRedirected)
+            TextWriter error, bool isErrorRedirected,
+            CancellationToken cancellationToken = default)
         {
             Input = input.GuardNotNull(nameof(input));
             IsInputRedirected = isInputRedirected;
@@ -51,13 +52,15 @@ namespace CliFx.Services
             IsOutputRedirected = isOutputRedirected;
             Error = error.GuardNotNull(nameof(error));
             IsErrorRedirected = isErrorRedirected;
+            _cancellationToken = cancellationToken;
         }
 
         /// <summary>
         /// Initializes an instance of <see cref="VirtualConsole"/>.
         /// </summary>
-        public VirtualConsole(TextReader input, TextWriter output, TextWriter error)
-            : this(input, true, output, true, error, true)
+        public VirtualConsole(TextReader input, TextWriter output, TextWriter error, 
+            CancellationToken cancellationToken = default)
+            : this(input, true, output, true, error, true, cancellationToken)
         {
         }
 
@@ -65,8 +68,8 @@ namespace CliFx.Services
         /// Initializes an instance of <see cref="VirtualConsole"/> using output stream (stdout) and error stream (stderr).
         /// Input stream (stdin) is replaced with a no-op stub.
         /// </summary>
-        public VirtualConsole(TextWriter output, TextWriter error)
-            : this(TextReader.Null, output, error)
+        public VirtualConsole(TextWriter output, TextWriter error, CancellationToken cancellationToken = default)
+            : this(TextReader.Null, output, error, cancellationToken)
         {
         }
 
@@ -74,8 +77,8 @@ namespace CliFx.Services
         /// Initializes an instance of <see cref="VirtualConsole"/> using output stream (stdout).
         /// Input stream (stdin) and error stream (stderr) are replaced with no-op stubs.
         /// </summary>
-        public VirtualConsole(TextWriter output)
-            : this(output, TextWriter.Null)
+        public VirtualConsole(TextWriter output, CancellationToken cancellationToken = default)
+            : this(output, TextWriter.Null, cancellationToken)
         {
         }
 
@@ -87,14 +90,6 @@ namespace CliFx.Services
         }
 
         /// <inheritdoc />
-        public CancellationToken CancellationToken => _cancellationTokenSource.Token;
-
-        /// <summary>
-        /// Simulates cancellation.
-        /// </summary>
-        public void Cancel()
-        {
-            _cancellationTokenSource.Cancel();
-        }
+        public CancellationToken GetCancellationToken() => _cancellationToken;
     }
 }

Readme.md

@@ -24,6 +24,7 @@ _CliFx is to command line interfaces what ASP.NET Core is to web applications._
 - Resolves commands and options using attributes
 - Handles options of various types, including custom types
 - Supports multi-level command hierarchies
+- Allows cancellation
 - Generates contextual help text
 - Prints errors and routes exit codes on exceptions
 - Highly testable and easy to debug
@@ -99,7 +100,7 @@ public class LogCommand : ICommand
 
 By implementing `ICommand` this class also provides `ExecuteAsync` method. This is the method that gets called when the user invokes the command. Its return type is `Task` in order to facilitate asynchronous execution, but if your command runs synchronously you can simply return `Task.CompletedTask`.
 
-The `ExecuteAsync` method also takes an instance of `IConsole` as a parameter. You should use this abstraction to interact with the console instead of calling `System.Console` so that your commands are testable.
+The `ExecuteAsync` method also takes an instance of `IConsole` as a parameter. You should use the `console` parameter in places where you would normally use `System.Console`, in order to make your command testable.
 
 Finally, the command defined above can be executed from the command line in one of the following ways:
 
@@ -215,6 +216,30 @@ public class SecondSubCommand : ICommand
 }
 ```
 
+### Cancellation
+
+It is possible to gracefully cancel execution of a command and preform any necessary cleanup. By default an app gets forcefully killed when it receives an interrupt signal (Ctrl+C or Ctrl+Break). You can call `console.GetCancellationToken()` to override the default behavior and get `CancellationToken` that represents the first interrupt signal. Second interrupt signal terminates an app immediately. Note that the code that executes before the first call to `GetCancellationToken` will not be cancellation aware.
+
+You can pass `CancellationToken` around and check its state. 
+
+Cancelled or terminated app returns non-zero exit code.
+
+```c#
+[Command("cancel")]
+public class CancellableCommand : ICommand
+{
+    public async Task ExecuteAsync(IConsole console)
+    {
+        console.Output.WriteLine("Printed");
+
+        // Long-running cancellable operation that throws when canceled
+        await Task.Delay(Timeout.InfiniteTimeSpan, console.GetCancellationToken());
+
+        console.Output.WriteLine("Never printed");
+    }
+}
+```
+
 ### Dependency injection
 
 CliFx uses an implementation of `ICommandFactory` to initialize commands and by default it only works with types that have parameterless constructors.
@@ -476,4 +501,4 @@ CliFx is made out of "Cli" for "Command Line Interface" and "Fx" for "Framework"
 
 ## Donate
 
-If you really like my projects and want to support me, consider donating to me on [Patreon](https://patreon.com/tyrrrz) or [BuyMeACoffee](https://buymeacoffee.com/tyrrrz). All donations are optional and are greatly appreciated. 🙏
+If you really like my projects and want to support me, consider donating to me on [Patreon](https://patreon.com/tyrrrz) or [BuyMeACoffee](https://buymeacoffee.com/tyrrrz). All donations are optional and are greatly appreciated. 🙏