History for TextPrompt to emulate shell history-style functionality

[seanmcelroy]

Greetings,

I'd like some input as to what others think about a new feature that would allow TextPrompt to support up/down arrow key scrolling of a history of items. The purpose of this feature is to support an experience in the console similar to how a terminal shell history works, where previously-entered commands can be enumerated by hitting 'up arrow' to see progressively older entries, or 'down arrow' to scroll back towards newer entries, eventually erasing that history if down was hit the same number of times as up. I have a use case that gathers input from a TextPrompt in a long-running do/while loop to provide an interactive CLI experience, and a scrollable history of previously entered commands would be useful. I'm unable to emulate this outside of a modification to TextPrompt, as internally, TextPrompt does a ReadKeyAsync() on an IAnsiConsole, which prevents me from separately capturing an up or down arrow key press consistently.

The design I would propose is to add a new nullable string enumerable property on TextPrompt called History that can contain any enumerable of previous text inputs the programmer wants to make available for scrolling. If this enumerable is null or empty, there is no change in behavior. If this is supplied, it is passed on down into AnsiConsoleExtensions.ReadLine, where it is used when an ConsoleKey.UpArrow or a ConsoleKey.DownArrow key is pressed.

Because users might print something to the console, such as a styled prompt (which I do with a "[green]>[/]" parameter to TextPrompt's constructor), replacing text works by moving the cursor left the number of spaces of the current length of text recorded by the TextPrompt, overwriting it with spaces, then moving the cursor left again by the number of spaces of the current length of text, and then writing the appropriate history entry. I'm not certain this accommodates every unique styling situation, and I'm particularly interested in test cases that might challenge this approach.

I have a working implementation of this idea along with passing unit tests (but no documentation updates yet) available in my forked feature branch here: https://github.com/seanmcelroy/spectre.console/tree/textprompt-history

I would welcome feedback about the idea, design, and implementation. If this is something a maintainer would consider accepting as a feature, I would proceed by opening an issue, incorporating feedback, and submitting this as a pull request.

Thank you for your consideration!

-Sean

[RobertK66]

Ok, I used your branch and could easily replace my clumsy KeyRead() loop. It took me some time to figure out how to 'enable' the feature by providing the History List from the outside of the Prompt Object and also that I am responsible on my side to archive a line. In hindsight I think this is not a bad idea, because I can decide on my own (e.g. not to store empty lines even when they are treated as valid in my command loop):

The Up/Down does work but the down arrow has a wrong border check 😄! You do not get down to the latest entry here. I think you have to change line 104 of the AnsiConsoleExtensions.Input.cs:

That said, I do think this is a valuable feature to add. Maybe you could consider to make it someway configurable. Either by adding the History as optional Constructor parameter with null as default, or you could instantiate it as static if not provided.

Other Option would be to add another Method to the TextPromptExtensions (like the AllowEmpty()). Could be somewhat like
.UseHistory(IEnumerable<string> lines, boolean autoStoreAll = false) {...}

So thx. for your work here and looking forward for a enhanced version :-)....

[seanmcelroy]

Thank you so much for your feedback @RobertK66!

I fixed that border check issue you found and added a .AddHistory() extension method to closely mirror the signature of .AddChoices(). I thought that suggestion was cleanest so I could minimize my impact on existing function signatures.

For any that read this afterwards, this is a small test harness that demonstrates how to use this feature that can be compiled as a simple C# console app:

using Spectre.Console;

internal class Program
{
    private static int Main()
    {
        AnsiConsole.MarkupLine("[bold fuchsia]spectre.console textprompt-history test harness[/]");

        List<string> history = [];

        do
        {
            string? input = AnsiConsole.Prompt(new TextPrompt<string>("[green]>[/]").AddHistory(history));
            if (!string.IsNullOrWhiteSpace(input))
                history.Add(input);

        } while (true);
    }
}

I also checked in some documentation to the docs/ project that provides a similar AddHistory() usage example. Again, I really appreciate your thoughts and feedback - you definitely helped me improve upon this idea. :)

[RobertK66]

yaw.
I would vote for it, if you get it on this list: #1517
There are some other TextPrompt related things there. Maybe a more generell issue/pull request titled 'Enhanced TextPrompt' would do the trick to get attention from maintainers ;-) ... (For me it seems they are working towards a 1.0 release at this moment. I am only a (rare) user of this package here.)

[RobertK66]

some 2nd thoughts:

• "Save the typed line": (I just tried this in one of my wsl shell (assume this is bash) as I am not really a linux/cli junky and it has this feature in place): You could save the already typed text when 'leaving' with the first Arrow Up key. And then you could restore this line 'after the last' history entry for even more user convenience....
• Generally provide a way to allow for custom implemented (Text)Prompts to be added. (@FrankRay78: Maybe this is already possible? maybe with registering somehow in DI? Do you already consider such use cases here Registrar/Resolver Redesign #1657 ? It would completely obsolete feature wishes along this line: Key Listener for Enhanced Input Handling #1606

[patriksvensson]

@seanmcelroy We try to limit the number of extensions in the main Spectre.Console library, especially around interactivity, but I encourage you to release something like this as an extension in the Spectre.Console community.

If you want inspiration, the Spectre.Console team has created something similar that you might find helpful as an inspiration: https://github.com/spectreconsole/radline/

[seanmcelroy]

Thank you for the note @patriksvensson! Given your feedback, I took your advice and released it as an extension here: https://github.com/seanmcelroy/TextPromptWithHistory

Also, FYI @RobertK66 - I will take your additional suggestions under consideration there, and I published this extension as a NuGet package in case you would like to use it ( com.seanmcelroy.Spectre.Console.Community.TextPromptWithHistory ). I do agree the saved text preservation would be a good and straightforward edit to make. Not sure on the DI-front, but I will look into it separately. There's some innards I had to clone because of sealed/internal restrictions that prevent TextPrompt from being subclassed or extended out of the box, so it may not be the best use case for a DI approach. I'll check, though!

I appreciate all the feedback and guidance. It was a fun contribution to make given the participation.

[RobertK66]

@seanmcelroy : I switched to your package and it works like described 👍!

Forget about "the DI stuff". It was my (wrong) assumption that you would need to replace some internals with registering own implementations. I was not aware that it is possible to provide your own IPrompt<> class and use a separate ReadLine provided by extension method of ANSIConsole.Input. Seems to do the trick. 😉. I am really happy to put my keyhandler into retirement, because I always had annoying issues with tabs and backspaces when trying to recover the cursor position "from the outside".....