Subject: bug#63399: 28.2; Documentation for yes-or-no-p wrong/different between docstring and lispref

From: Michael Albinus <[email-masked]>
Date: Wed, 10 May 2023 12:08:24 +0200

Tim Landscheidt <[email-masked]> writes:

Hi,

> With the big caveat that I have never looked deeper at
> Emacs's C code, the source in src/fns.c does not appear to
> change the prompt given as an argument in any way, but just
> append yes-or-no-prompt to it.
>
> Also, (elisp) Yes-or-No Queries reads (since 7f53446a10ea;
> doc/lispref/minibuf.texi):
>
> | […]
>
> |      Here is an example:
>
> |           (yes-or-no-p "Do you really want to remove everything?")
>
> |           ;; After evaluation of the preceding expression,
> |           ;;   the following prompt appears,
> |           ;;   with an empty minibuffer:
>
> |           ---------- Buffer: minibuffer ----------
> |           Do you really want to remove everything? (yes or no)
> |           ---------- Buffer: minibuffer ----------
>
> | […]
>
> This is not the actual result: (yes-or-no-p "Do you really
> want to remove everything?") gives the prompt "Do you really
> want to remove everything?(yes or no) ", i. e., the space
> before the parenthesis is missing.

I guess we should pad the prompt with a trailing space, if there isn't
any already. As we do in `y-or-no-p'. What about the appended patch?
Documentation must be updated as well, of course.

Best regards, Michael.

diff --git a/src/fns.c b/src/fns.c
index bb6efdda655..b081cb225e1 100644
--- a/src/fns.c
+++ b/src/fns.c
@@ -26,6 +26,7 @@ Copyright (C) 1985-2023 Free Software Foundation, Inc.
 #include <intprops.h>
 #include <vla.h>
 #include <errno.h>
+#include <ctype.h>

 #include "lisp.h"
 #include "bignum.h"
@@ -3234,6 +3235,12 @@ DEFUN ("yes-or-no-p", Fyes_or_no_p, Syes_or_no_p, 1, 1, 0,
   if (use_short_answers)
     return call1 (intern ("y-or-n-p"), prompt);

+  {
+    char *s = SSDATA (prompt);
+    ptrdiff_t len = strlen (s);
+    if (!(len == 0) && !(isspace (s[len - 1])))
+      prompt = CALLN (Fconcat, prompt, make_string (" ", 1));
+  }
   prompt = CALLN (Fconcat, prompt, Vyes_or_no_prompt);

   specpdl_ref count = SPECPDL_INDEX ();