Support for Escape key in SelectionPrompt and MultiSelectionPrompt

[jariq]

Let's talk about SelectionPrompt in its simplest form e.g.

var selection = AnsiConsole.Prompt(
	new SelectionPrompt<string>()
	.AddChoices(new string[] { "a", "b", "c", "d" }));

User can use Up and Down arrows to change selected item and Spacebar or Enter to confirm the selection.
However in my application I'm missing an option to cancel the selection entirely e.g by pressing Escape key.
As a workaround I'm adding a special item at the beginning or at the end of the list and I handle its selection in a special way.
However in longer lists this first requires user to get to the top or bottom of the list by pressing Home or End key.
I believe Escape key would be more convenient and most importantly it would help consumer code to be shorter and easier to understand.

So I would like to add support for Escape key to SelectionPrompt and MultiSelectionPrompt.
Basic idea is that prompt ends when user presses Escape key and it somehow indicates to the caller it was cancelled (e.g. by returning null, setting some new property to true, throwing some specific exception etc.).

Is this a feature that you would be willing to merge to Spectre.Console?

[jariq]

I just submitted one possible solution as #711

[patriksvensson]

Sorry for not getting back sooner about this. We've all been pretty swamped, but we will try to get around to reviewing it this weekend.

[jariq]

Thanks, but there's no need to hurry. I'm now developing my app with a local copy of spectre.console which includes proposed changes so I'm not blocked on this anymore.

[abpiskunov]

Any progress here? We also interested in this functionality.

[jariq]

I'm closing this discussion as I'm no longer interested in working on this feature.

[ZelAnton]

var console = new EscapeCancellableConsole(AnsiConsole.Console);

string? selected;
try
{
     selected = await console.PromptAsync(selectionPrompt);
}
catch (OperationCanceledException)
{
    selected = null;
}

// Processing selected...

exit;

sealed class EscapeCancellableConsole : IAnsiConsole
{
    readonly EscapeCancellableInput input;
    readonly IAnsiConsole console;

    public EscapeCancellableConsole(IAnsiConsole console)
    {
        this.console = console;
        input = new EscapeCancellableInput(console.Input, EscapeCancellationTokenSource);
    }

    public CancellationTokenSource EscapeCancellationTokenSource { get; } = new();

    public Profile Profile => console.Profile;
    public IAnsiConsoleCursor Cursor => console.Cursor;
    public IAnsiConsoleInput Input => input;
    public IExclusivityMode ExclusivityMode => console.ExclusivityMode;
    public RenderPipeline Pipeline => console.Pipeline;
    public void Clear(bool home) => console.Clear(home);
    public void Write(IRenderable renderable) => console.Write(renderable);

    public Task<T> PromptAsync<T>(IPrompt<T> prompt, CancellationToken cancellationToken = default)
        => AnsiConsoleExtensions.PromptAsync(this, prompt, GetMergedCancellationToken(cancellationToken));

    CancellationToken GetMergedCancellationToken(CancellationToken cancellationToken)
        => cancellationToken == CancellationToken.None || cancellationToken == EscapeCancellationTokenSource.Token
        ? EscapeCancellationTokenSource.Token
        : CancellationTokenSource.CreateLinkedTokenSource(cancellationToken, EscapeCancellationTokenSource.Token).Token;
}

sealed class EscapeCancellableInput(IAnsiConsoleInput originalInput, CancellationTokenSource cts) : IAnsiConsoleInput
{
    public bool IsKeyAvailable() => originalInput.IsKeyAvailable();

    public ConsoleKeyInfo? ReadKey(bool intercept)
    {
        var key = originalInput.ReadKey(intercept);
        if (key?.Key == ConsoleKey.Escape)
        {
            cts.Cancel();
        }

        return key;
    }

    public async Task<ConsoleKeyInfo?> ReadKeyAsync(bool intercept, CancellationToken cancellationToken)
    {
        var key = await originalInput.ReadKeyAsync(intercept, cancellationToken);
        if (key?.Key == ConsoleKey.Escape)
        {
            await cts.CancelAsync();
        }

        return key;
    }
}

https://gist.github.com/ZelAnton/9b631ad409f6a2ebb6730824596a3b3d

[z00mable]

@ZelAnton Thank you. You're implementation works well. Since I use AskAsync a lot this extension is also needed in EscapeCancellableConsole class:

public Task<T> AskAsync<T>(string prompt, CancellationToken cancellationToken = default) => AnsiConsoleExtensions.AskAsync<T>(this, prompt, GetMergedCancellationToken(cancellationToken));