Add support for synchronous prompt cancellation

The current prompt APIs suffer from a few problems.

* The syncrhonous `ReadKey` method does not support cancellation.
* The syncrhonous `ReadKey` method returns a nullable `ConsoleKeyInfo` struct but `System.Console.ReadKey` can never return a nullable `ConsoleKeyInfo`.
* The asyncrhonous `ReadKeyAsync` method can return `null` only if cancellation has been requested. But this can never actually happen since [Fix deadlock when cancelling prompts (spectreconsole#1439)](spectreconsole#1439) was merged.

Here's are the problematic implementation (before this commit fixes it):

```csharp
public ConsoleKeyInfo? ReadKey(bool intercept)
{
    return System.Console.ReadKey(intercept);
}

public async Task<ConsoleKeyInfo?> ReadKeyAsync(bool intercept, CancellationToken cancellationToken)
{
    while (true)
    {
        if (cancellationToken.IsCancellationRequested)
        {
            return null;
        }

        if (System.Console.KeyAvailable)
        {
            break;
        }

        await Task.Delay(5, cancellationToken).ConfigureAwait(false);
    }

    return ReadKey(intercept);
}
```

Note that adding a `CancellationToken` parameter and returning `ConsoleKeyInfo` instead of `ConsoleKeyInfo?` is a breaking change since it modifies the signatures of the public `IAnsiConsoleInput` interface. But this should not be an issue since it's impossible to use another implentation than `DefaultInput` when used through `AnsiConsole.Create(AnsiConsoleSettings settings)`.  

I have also searched for [implementers of IAnsiConsoleInput](https://grep.app/search?q=IAnsiConsoleInput) and I think this change won't break anything since nobody actually implemented `IAnsiConsoleInput`. Only exising implementations which have been udated are being used (at least across a half million public git repos).

The addition of the `CancellationToken` to `IPrompt.Show(IAnsiConsole console, CancellationToken cancellationToken = default)` is also a breaking change but it should be mitigated since it has bee introduced with a default value.

src/Spectre.Console.Testing/TestConsoleInput.cs

@@ -77,19 +77,21 @@ public bool IsKeyAvailable()
     }
 
     /// <inheritdoc/>
-    public ConsoleKeyInfo? ReadKey(bool intercept)
+    public ConsoleKeyInfo ReadKey(bool intercept, CancellationToken cancellationToken)
     {
         if (_input.Count == 0)
         {
             throw new InvalidOperationException("No input available.");
         }
 
+        cancellationToken.ThrowIfCancellationRequested();
+
         return _input.Dequeue();
     }
 
     /// <inheritdoc/>
-    public Task<ConsoleKeyInfo?> ReadKeyAsync(bool intercept, CancellationToken cancellationToken)
+    public Task<ConsoleKeyInfo> ReadKeyAsync(bool intercept, CancellationToken cancellationToken)
     {
-        return Task.FromResult(ReadKey(intercept));
+        return Task.FromResult(ReadKey(intercept, cancellationToken));
     }
 }

src/Spectre.Console/AnsiConsole.Prompt.cs

@@ -10,26 +10,28 @@ public static partial class AnsiConsole
     /// </summary>
     /// <typeparam name="T">The prompt result type.</typeparam>
     /// <param name="prompt">The prompt to display.</param>
+    /// <param name="cancellationToken">The token to monitor for cancellation requests.</param>
     /// <returns>The prompt input result.</returns>
-    public static T Prompt<T>(IPrompt<T> prompt)
+    public static T Prompt<T>(IPrompt<T> prompt, CancellationToken cancellationToken = default)
     {
         if (prompt is null)
         {
             throw new ArgumentNullException(nameof(prompt));
         }
 
-        return prompt.Show(Console);
+        return prompt.Show(Console, cancellationToken);
     }
 
     /// <summary>
     /// Displays a prompt to the user.
     /// </summary>
     /// <typeparam name="T">The prompt result type.</typeparam>
     /// <param name="prompt">The prompt markup text.</param>
+    /// <param name="cancellationToken">The token to monitor for cancellation requests.</param>
     /// <returns>The prompt input result.</returns>
-    public static T Ask<T>(string prompt)
+    public static T Ask<T>(string prompt, CancellationToken cancellationToken = default)
     {
-        return new TextPrompt<T>(prompt).Show(Console);
+        return new TextPrompt<T>(prompt).Show(Console, cancellationToken);
     }
 
     /// <summary>
@@ -38,26 +40,28 @@ public static T Ask<T>(string prompt)
     /// <typeparam name="T">The prompt result type.</typeparam>
     /// <param name="prompt">The prompt markup text.</param>
     /// <param name="defaultValue">The default value.</param>
+    /// <param name="cancellationToken">The token to monitor for cancellation requests.</param>
     /// <returns>The prompt input result.</returns>
-    public static T Ask<T>(string prompt, T defaultValue)
+    public static T Ask<T>(string prompt, T defaultValue, CancellationToken cancellationToken = default)
     {
         return new TextPrompt<T>(prompt)
             .DefaultValue(defaultValue)
-            .Show(Console);
+            .Show(Console, cancellationToken);
     }
 
     /// <summary>
     /// Displays a prompt with two choices, yes or no.
     /// </summary>
     /// <param name="prompt">The prompt markup text.</param>
     /// <param name="defaultValue">Specifies the default answer.</param>
+    /// <param name="cancellationToken">The token to monitor for cancellation requests.</param>
     /// <returns><c>true</c> if the user selected "yes", otherwise <c>false</c>.</returns>
-    public static bool Confirm(string prompt, bool defaultValue = true)
+    public static bool Confirm(string prompt, bool defaultValue = true, CancellationToken cancellationToken = default)
     {
         return new ConfirmationPrompt(prompt)
         {
             DefaultValue = defaultValue,
         }
-        .Show(Console);
+        .Show(Console, cancellationToken);
     }
 }

src/Spectre.Console/Extensions/AnsiConsoleExtensions.Input.cs

@@ -5,7 +5,18 @@ namespace Spectre.Console;
 /// </summary>
 public static partial class AnsiConsoleExtensions
 {
-    internal static async Task<string> ReadLine(this IAnsiConsole console, Style? style, bool secret, char? mask, IEnumerable<string>? items = null, CancellationToken cancellationToken = default)
+    internal static string ReadLine(this IAnsiConsole console, Style? style, bool secret, char? mask, IEnumerable<string>? items = null, CancellationToken cancellationToken = default)
+    {
+        return ReadLineImpl(console, style, secret, mask, async: false, items, cancellationToken).GetAwaiter().GetResult();
+    }
+
+    internal static async Task<string> ReadLineAsync(this IAnsiConsole console, Style? style, bool secret, char? mask, IEnumerable<string>? items = null, CancellationToken cancellationToken = default)
+    {
+        return await ReadLineImpl(console, style, secret, mask, async: true, items, cancellationToken).ConfigureAwait(false);
+    }
+
+    [SuppressMessage("ReSharper", "MethodHasAsyncOverload")]
+    private static async Task<string> ReadLineImpl(IAnsiConsole console, Style? style, bool secret, char? mask, bool async, IEnumerable<string>? items = null, CancellationToken cancellationToken = default)
     {
         if (console is null)
         {
@@ -19,14 +30,16 @@ internal static async Task<string> ReadLine(this IAnsiConsole console, Style? st
 
         while (true)
         {
-            cancellationToken.ThrowIfCancellationRequested();
-            var rawKey = await console.Input.ReadKeyAsync(true, cancellationToken).ConfigureAwait(false);
-            if (rawKey == null)
+            ConsoleKeyInfo key;
+            if (async)
             {
-                continue;
+                key = await console.Input.ReadKeyAsync(true, cancellationToken).ConfigureAwait(false);
+            }
+            else
+            {
+                key = console.Input.ReadKey(true, cancellationToken);
             }
 
-            var key = rawKey.Value;
             if (key.Key == ConsoleKey.Enter)
             {
                 return text;

src/Spectre.Console/Extensions/AnsiConsoleExtensions.Prompt.cs

@@ -11,15 +11,16 @@ public static partial class AnsiConsoleExtensions
     /// <typeparam name="T">The prompt result type.</typeparam>
     /// <param name="console">The console.</param>
     /// <param name="prompt">The prompt to display.</param>
+    /// <param name="cancellationToken">The token to monitor for cancellation requests.</param>
     /// <returns>The prompt input result.</returns>
-    public static T Prompt<T>(this IAnsiConsole console, IPrompt<T> prompt)
+    public static T Prompt<T>(this IAnsiConsole console, IPrompt<T> prompt, CancellationToken cancellationToken = default)
     {
         if (prompt is null)
         {
             throw new ArgumentNullException(nameof(prompt));
         }
 
-        return prompt.Show(console);
+        return prompt.Show(console, cancellationToken);
     }
 
     /// <summary>
@@ -28,10 +29,11 @@ public static T Prompt<T>(this IAnsiConsole console, IPrompt<T> prompt)
     /// <typeparam name="T">The prompt result type.</typeparam>
     /// <param name="console">The console.</param>
     /// <param name="prompt">The prompt markup text.</param>
+    /// <param name="cancellationToken">The token to monitor for cancellation requests.</param>
     /// <returns>The prompt input result.</returns>
-    public static T Ask<T>(this IAnsiConsole console, string prompt)
+    public static T Ask<T>(this IAnsiConsole console, string prompt, CancellationToken cancellationToken = default)
     {
-        return new TextPrompt<T>(prompt).Show(console);
+        return new TextPrompt<T>(prompt).Show(console, cancellationToken);
     }
 
     /// <summary>
@@ -41,12 +43,13 @@ public static T Ask<T>(this IAnsiConsole console, string prompt)
     /// <param name="console">The console.</param>
     /// <param name="prompt">The prompt markup text.</param>
     /// <param name="culture">Specific CultureInfo to use when converting input.</param>
+    /// <param name="cancellationToken">The token to monitor for cancellation requests.</param>
     /// <returns>The prompt input result.</returns>
-    public static T Ask<T>(this IAnsiConsole console, string prompt, CultureInfo? culture)
+    public static T Ask<T>(this IAnsiConsole console, string prompt, CultureInfo? culture, CancellationToken cancellationToken = default)
     {
         var textPrompt = new TextPrompt<T>(prompt);
         textPrompt.Culture = culture;
-        return textPrompt.Show(console);
+        return textPrompt.Show(console, cancellationToken);
     }
 
     /// <summary>
@@ -55,13 +58,14 @@ public static T Ask<T>(this IAnsiConsole console, string prompt, CultureInfo? cu
     /// <param name="console">The console.</param>
     /// <param name="prompt">The prompt markup text.</param>
     /// <param name="defaultValue">Specifies the default answer.</param>
+    /// <param name="cancellationToken">The token to monitor for cancellation requests.</param>
     /// <returns><c>true</c> if the user selected "yes", otherwise <c>false</c>.</returns>
-    public static bool Confirm(this IAnsiConsole console, string prompt, bool defaultValue = true)
+    public static bool Confirm(this IAnsiConsole console, string prompt, bool defaultValue = true, CancellationToken cancellationToken = default)
     {
         return new ConfirmationPrompt(prompt)
         {
             DefaultValue = defaultValue,
         }
-        .Show(console);
+        .Show(console, cancellationToken);
     }
 }

src/Spectre.Console/IAnsiConsoleInput.cs

@@ -6,24 +6,30 @@ namespace Spectre.Console;
 public interface IAnsiConsoleInput
 {
     /// <summary>
-    /// Gets a value indicating whether or not
-    /// there is a key available.
+    /// Gets a value indicating whether there is a key available or not.
     /// </summary>
     /// <returns><c>true</c> if there's a key available, otherwise <c>false</c>.</returns>
     bool IsKeyAvailable();
 
     /// <summary>
     /// Reads a key from the console.
     /// </summary>
-    /// <param name="intercept">Whether or not to intercept the key.</param>
+    /// <param name="intercept">
+    /// Determines whether to display the pressed key in the console window.
+    /// <see langword="true"/> to not display the pressed key; otherwise, <see langword="false"/>.
+    /// </param>
+    /// <param name="cancellationToken">The token to monitor for cancellation requests.</param>
     /// <returns>The key that was read.</returns>
-    ConsoleKeyInfo? ReadKey(bool intercept);
+    ConsoleKeyInfo ReadKey(bool intercept, CancellationToken cancellationToken);
 
     /// <summary>
     /// Reads a key from the console.
     /// </summary>
-    /// <param name="intercept">Whether or not to intercept the key.</param>
+    /// <param name="intercept">
+    /// Determines whether to display the pressed key in the console window.
+    /// <see langword="true"/> to not display the pressed key; otherwise, <see langword="false"/>.
+    /// </param>
     /// <param name="cancellationToken">The token to monitor for cancellation requests.</param>
     /// <returns>The key that was read.</returns>
-    Task<ConsoleKeyInfo?> ReadKeyAsync(bool intercept, CancellationToken cancellationToken);
+    Task<ConsoleKeyInfo> ReadKeyAsync(bool intercept, CancellationToken cancellationToken);
 }

src/Spectre.Console/Internal/DefaultInput.cs

@@ -11,46 +11,45 @@ public DefaultInput(Profile profile)
 
     public bool IsKeyAvailable()
     {
-        if (!_profile.Capabilities.Interactive)
-        {
-            throw new InvalidOperationException("Failed to read input in non-interactive mode.");
-        }
+        EnsureInteractive();
 
         return System.Console.KeyAvailable;
     }
 
-    public ConsoleKeyInfo? ReadKey(bool intercept)
+    public ConsoleKeyInfo ReadKey(bool intercept, CancellationToken cancellationToken)
     {
-        if (!_profile.Capabilities.Interactive)
+        cancellationToken.ThrowIfCancellationRequested();
+
+        EnsureInteractive();
+
+        while (!System.Console.KeyAvailable)
         {
-            throw new InvalidOperationException("Failed to read input in non-interactive mode.");
+            cancellationToken.ThrowIfCancellationRequested();
+            Thread.Sleep(5);
         }
 
         return System.Console.ReadKey(intercept);
     }
 
-    public async Task<ConsoleKeyInfo?> ReadKeyAsync(bool intercept, CancellationToken cancellationToken)
+    public async Task<ConsoleKeyInfo> ReadKeyAsync(bool intercept, CancellationToken cancellationToken)
     {
-        if (!_profile.Capabilities.Interactive)
-        {
-            throw new InvalidOperationException("Failed to read input in non-interactive mode.");
-        }
+        cancellationToken.ThrowIfCancellationRequested();
 
-        while (true)
-        {
-            if (cancellationToken.IsCancellationRequested)
-            {
-                return null;
-            }
-
-            if (System.Console.KeyAvailable)
-            {
-                break;
-            }
+        EnsureInteractive();
 
+        while (!System.Console.KeyAvailable)
+        {
             await Task.Delay(5, cancellationToken).ConfigureAwait(false);
         }
 
-        return ReadKey(intercept);
+        return System.Console.ReadKey(intercept);
+    }
+
+    private void EnsureInteractive()
+    {
+        if (!_profile.Capabilities.Interactive)
+        {
+            throw new InvalidOperationException("Failed to read input in non-interactive mode.");
+        }
     }
 }

src/Spectre.Console/Prompts/ConfirmationPrompt.cs

@@ -68,13 +68,18 @@ public ConfirmationPrompt(string prompt)
     }
 
     /// <inheritdoc/>
-    public bool Show(IAnsiConsole console)
+    public bool Show(IAnsiConsole console, CancellationToken cancellationToken = default)
     {
-        return ShowAsync(console, CancellationToken.None).GetAwaiter().GetResult();
+        return ShowImpl(console, async: false, cancellationToken).GetAwaiter().GetResult();
     }
 
     /// <inheritdoc/>
     public async Task<bool> ShowAsync(IAnsiConsole console, CancellationToken cancellationToken)
+    {
+        return await ShowImpl(console, async: true, cancellationToken).ConfigureAwait(false);
+    }
+
+    private async Task<bool> ShowImpl(IAnsiConsole console, bool async, CancellationToken cancellationToken)
     {
         var comparer = Comparer ?? StringComparer.CurrentCultureIgnoreCase;
 
@@ -89,7 +94,15 @@ public async Task<bool> ShowAsync(IAnsiConsole console, CancellationToken cancel
             .AddChoice(Yes)
             .AddChoice(No);
 
-        var result = await prompt.ShowAsync(console, cancellationToken).ConfigureAwait(false);
+        char result;
+        if (async)
+        {
+            result = await prompt.ShowAsync(console, cancellationToken).ConfigureAwait(false);
+        }
+        else
+        {
+            result = prompt.Show(console, cancellationToken);
+        }
 
         return comparer.Compare(Yes.ToString(), result.ToString()) == 0;
     }

src/Spectre.Console/Prompts/IPrompt.cs

@@ -10,8 +10,9 @@ public interface IPrompt<T>
     /// Shows the prompt.
     /// </summary>
     /// <param name="console">The console.</param>
+    /// <param name="cancellationToken">The token to monitor for cancellation requests.</param>
     /// <returns>The prompt input result.</returns>
-    T Show(IAnsiConsole console);
+    T Show(IAnsiConsole console, CancellationToken cancellationToken = default);
 
     /// <summary>
     /// Shows the prompt asynchronously.