Re: result of completing-read contradicting require-match

[Yuri Khan]

On Sun, 3 Jul 2022 at 02:29, Jean Louis <bugs@gnu.support> wrote:

> REQUIRE-MATCH can take the following values:
> - a function, which will be called with the input as the parameter.
>   If it returns a non-nil value, the minibuffer is exited with that value.

> other way to persist asking until you get the true result is here:
>
> (defun rcd-repeat-until-not-empty-string (function &rest args)
>   "Repeat FUNCTION with optional ARGS until result is not empty string."
>   (let ((result))
>     (while (string-empty-p (setq result (apply function args))))
>       result))

Based on the quoted part of the docstring, you could probably pass a
function that returns t for an allowed value, and nil for disallowed
values, including an empty string or nil.