Re: completing-read depricated initial-input

[Philip Kaludercic]

Arash Esbati <arash@gnu.org> writes:

> Robert Pluim <rpluim@gmail.com> writes:
>
>>>>>>> On Thu, 23 Jun 2022 16:46:53 +0200, Arash Esbati <arash@gnu.org> said:
>>
>>     Arash> I'd say it's up to the AUCTeX maintainers to bump the minimum 
>> required
>>     Arash> Emacs version at a faster pace ;-)
>>
>> Either that, or they can depend on the 'compat' package, and then just
>> use emacs-28 features with wild abandon.
>
> Thanks for reminding me of compat.  I think compat-28.el has currently a
> bug since the return value of `format-prompt' is not the same as in
> Emacs>=28:
>
> (format-prompt "Foo" "")
> => "Foo: "
>
> This is what compat-28.el does:
>
> (defun compat-format-prompt (prompt default &rest format-args)
>   "Format PROMPT with DEFAULT.
> If FORMAT-ARGS is nil, PROMPT is used as a plain string.  If
> FORMAT-ARGS is non-nil, PROMPT is used as a format control
> string, and FORMAT-ARGS are the arguments to be substituted into
> it.  See `format' for details.
>
> If DEFAULT is a list, the first element is used as the default.
> If not, the element is used as is.
>
> If DEFAULT is nil or an empty string, no \"default value\" string
> is included in the return value."
>   (concat
>    (if (null format-args)
>        prompt
>      (apply #'format prompt format-args))
>    (and default
>         (or (not (stringp default))
>             (not (null default)))
>         ;;  (length> default 0) ; This is in Emacs stock version
>         (format " (default %s)"
>                 (if (consp default)
>                     (car default)
>                   default)))
>    ": "))
>
> (compat-format-prompt "Foo" "")
> => "Foo (default ): "
>
> compat doesn't check if DEFAULT is an empty string.  I'm CC'ing Philip,
> maybe he can comment.

You are right, this is a bug.  When "reimplementing" format-prompt with
backwards compatibility in mind, I replaced the (length> default 0) with
(not (null default)).  This would work on lists, but not on arrays.  I
have replaced it and updated the tests.

> Best, Arash