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

[Stephen Berman <stephen.berman@gmx.net>]

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On Thu, 07 Nov 2024 09:36:42 +0200 Eli Zaretskii <eliz@gnu.org> wrote:

>> From: Joseph Turner <joseph@breatheoutbreathe.in>
>> Date: Wed, 06 Nov 2024 12:06:02 -0800
>>
>> When used with `read-string' (and other read-* functions),
>> `format-prompt' DTRT:
>>
>> (let ((default "foo"))
>>   (read-string (format-prompt "Read" default) default))
>>
>> The prompt looks like: "Read (default foo): "
>>
>> However, `read-number' adds its own default argument:
>>
>> (let ((default 1))
>>   (read-number (format-prompt "Read" default) default))
>>
>> Prompt looks like: "Read (default 1) (default 1): "
>>
>> This patch makes the behavior of `read-number' consistent with other
>> read-* functions:
>
> Thanks.
>
> First, this should have been sent to our issue tracker, via
> report-emacs-bug or submit-emacs-patch.
>
> 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)

Steve Berman

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diff --git a/lisp/subr.el b/lisp/subr.el
index e630087b68f..8dcaef08b65 100644
--- a/lisp/subr.el
+++ b/lisp/subr.el
@@ -3432,12 +3432,18 @@ read-number
   (let ((n nil)
 	(default1 (if (consp default) (car default) default)))
     (when default1
-      (setq prompt
-	    (if (string-match "\\(\\):[ \t]*\\'" prompt)
-		(replace-match (format minibuffer-default-prompt-format default1) t t prompt 1)
-	      (replace-regexp-in-string "[ \t]*\\'"
-					(format minibuffer-default-prompt-format default1)
-					prompt t t))))
+      ;; If PROMPT uses `format-prompt', don't duplicate DEFAULT in
+      ;; the prompt string.
+      (if (string-match (regexp-quote
+			 (format minibuffer-default-prompt-format default1))
+			prompt)
+	  (setq default1 nil)
+        (setq prompt
+	      (if (string-match "\\(\\):[ \t]*\\'" prompt)
+		  (replace-match (format minibuffer-default-prompt-format default1) t t prompt 1)
+	        (replace-regexp-in-string "[ \t]*\\'"
+					  (format minibuffer-default-prompt-format default1)
+					  prompt t t)))))
     (while
 	(progn
 	  (let ((str (read-from-minibuffer