[small feature] Add \e string escape sequence

[Unknown6656]

Background

We currently have the following escape sequences in C# strings:

• \' - single quote, needed for character literals
• \" - double quote, needed for string literals
• \\ - backslash
• \0 - Unicode character 0
• \a - Alert (character 7)
• \b - Backspace (character 8)
• \f - Form feed (character 12)
• \n - New line (character 10)
• \r - Carriage return (character 13)
• \t - Horizontal tab (character 9)
• \v - Vertical tab (character 11)
• \uxxxx - Unicode escape sequence for character with hex value xxxx
• \xn[n][n][n] - Unicode escape sequence for character with hex value nnnn (variable length version of \uxxxx)
• \Uxxxxxxxx - Unicode escape sequence for character with hex value xxxxxxxx (for generating surrogates)

However, as I am working very often with VT100/ANSI escape codes, I do miss a short escape sequence for the character 0x1b, which is needed all the time in ANSI escape sequences.
Currently, I often write myself writing stuff like:

Console.Write("\u001b[4m\u001b[6m\u001b[38;2;205;20;60mThis is a bold, blinking, underlined, red text.\u001b[0mThis is a regular text.");

Actual Feature Request

I know that it only saves a couple of characters, but I'd really love to see \e as a shorthand for \u001b as a new escape sequence for C# strings, in order to enhance readability in the context of VT100/ANSI escape codes:

Console.Write("\e[4m\e[6m\e[38;2;205;20;60mThis is a bold, blinking, underlined, red text.\e[0mThis is a regular text.");

Implementation Cost

Hopefully, it should be low, as the internal translation would be identical to how e.g. \n gets translated to \u000a.

Alternatives

Alternatively, one can always use the following:

const char ESC = (char)0x1b;
Console.Write($"{ESC}[4m{ESC}[6m{ESC}[38;2;205;20;60mThis is a bold, blinking, underlined, red text.{ESC}[0mThis is a regular text.");

or:

static string escape(string code) => $"\u001b[{code}m";
Console.Write($"{escape("4")}{escape("6")}{escape("38;2;205;20;60")}This is a bold, blinking, underlined, red text.{escape("0")}This is a regular text.");

[CyrusNajmabadi]

I'd champion a proposal here. Having done the raw-strings-work, i know this would be a trivial thing to implement on compiler and IDE side.

[jnm2]

Another use case I've been involved with is low-level device communication, such as printer ESC/POS commands.

[Unknown6656]

@jnm2 good point. I'm currently writing the porposal, so I'll include that. feel free to drop some references here and I'll include them :)

[CyrusNajmabadi]

However, I've never written a correct/formal language feature proposal here. I'll give it a try and you can support me if you want to.

First, a reasonable way to do this (For a small tweak feature like this) would be to use this link:

Which will give you a template (also make a note saying Cyrus approved you opening this issue).

Second, try to make the spec include a 'diff' of the rules of the current language. For that, it would be basically specifying the changes you woudl make to: https://github.com/dotnet/csharpstandard/blob/standard-v6/standard/lexical-structure.md#6455-character-literals

you can use the ```diff tag for this purpose in the spec.

--

I would also nto go overboard at first. Just write up a simple first sketch. We can then help you revise as necessary. This will help avoid a lot of churn, and will hopefully save time for you :)

[jnm2]

The #csharp-lang-design channel at https://aka.ms/dotnet-discord is a great place for asking questions, too.

[jnm2]

@Unknown6656 Also see https://learn.microsoft.com/en-us/windows/uwp/devices-sensors/epson-esc-pos-with-formatting or https://reference.epson-biz.com/modules/ref_escpos/

[Unknown6656]

Closing in favor of #7400.
THanks @CyrusNajmabadi and @jnm2 for your input!