Re: Unexpected behavior of format-number with format-prompt

[Stephen Berman]

On Thu, 07 Nov 2024 16:47:40 +0200 Eli Zaretskii <eliz@gnu.org> wrote:

>> From: Stephen Berman <stephen.berman@gmx.net>
>> Cc: Joseph Turner <joseph@breatheoutbreathe.in>,  emacs-devel@gnu.org
>> Date: Thu, 07 Nov 2024 14:50:27 +0100
>>
>> > More to the point: we cannot possibly change the behavior of
>> > read-number in such a backward-incompatible way.  Especially since
>> > this behavior is old, and explicitly called out in the doc string.  It
>> > is perhaps unfortunate that read-number behaves differently in this
>> > manner, but I'm afraid we will have to live with this.
>>
>> Maybe something like the attached patch is acceptable?  With it,
>> evaluating each of the following prompts with "Enter (default 42): "
>>
>> (read-number "Enter: " 42)
>> (read-number (format-prompt "Enter" 42))
>> (read-number (format-prompt "Enter" 42) 42)
>
> This assumes that using the same format as
> minibuffer-default-prompt-format necessarily means that format-prompt
> is being used.  I'm not sure we can rely on that, it's too ad-hoc.

The patch itself does not assume format-prompt but only checks whether
the prompt uses minibuffer-default-prompt-format (which format-prompt
does); the following also prompt with "Enter (default 42): ":

(read-number (concat "Enter"
                     (format minibuffer-default-prompt-format 42)
                     ": "))

(read-number (concat "Enter:"
                     (format minibuffer-default-prompt-format 42)
                     ": ")
             42)

So the reference to format-prompt in the comment I added is misleading
and should be either removed or revised, e.g.: "If PROMPT uses
`minibuffer-default-prompt-format' (as e.g. with `format-prompt'), don't
duplicate DEFAULT in the prompt string."

Steve Berman