Readline behavior with colored custom prompt

[Matthew Keeter]

Hi all,

I’m seeing strange behavior with readline's interaction with ANSI codes.

Here’s a minimal sample script that reproduces the behavior:

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(use-modules (system repl repl) (system repl common))
(use-modules (ice-9 readline))

(define (custom-prompt repl)  "\x1b[34m :D > \x1b[0m")

(activate-readline)
(repl-default-option-set! 'prompt custom-prompt)

(start-repl)
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

Run this and you’ll get a Guile shell.  Into that shell, type

    '(1 2 3 4 5 6 7 8 9 10)

The final parenthesis will highlight a character midway through the string
(instead of the first parenthesis).

The same issues happen if you try to scroll through history: lines end up
overlapping in strange ways.

Removing the ANSI codes from custom-prompt resolves the issue, but I’d really
like to have a colored prompt and correct readline behavior.

Does anyone have any ideas?

Thanks,
Matt