Re: emacs-28 a866674b2a: Fix inaccuracies in "lax search" documentation

[Robert Pluim]

>>>>> On Wed, 31 Aug 2022 20:22:30 +0300, Eli Zaretskii <eliz@gnu.org> said:

    >> From: Juri Linkov <juri@linkov.net>
    >> Cc: Eli Zaretskii <eliz@gnu.org>,  emacs-devel@gnu.org
    >> Date: Wed, 31 Aug 2022 20:13:45 +0300
    >> 
    >> I see it the other way around - that pleads for fixing
    >> `read-char-from-minibuffer':

    Eli> You do?

    Eli> If read-char-from-minibuffer is supposed to return a single character,
    Eli> it cannot return nil (or anything else that indicates empty input).
    Eli> If you make such a change, expect it to break many use cases
    Eli> elsewhere.

    Eli> To me, the above says that read-char-from-minibuffer is not the right
    Eli> tool for this job.

Hereʼs the kind of thing I had in mind:

diff --git a/lisp/international/mule-cmds.el b/lisp/international/mule-cmds.el
index 12896cc4b0..4137642528 100644
--- a/lisp/international/mule-cmds.el
+++ b/lisp/international/mule-cmds.el
@@ -3195,7 +3195,7 @@ read-char-by-name-sort
   :group 'mule
   :version "28.1")
 
-(defun read-char-by-name (prompt)
+(defun read-char-by-name (prompt &optional allow-single)
   "Read a character by its Unicode name or hex number string.
 Display PROMPT and read a string that represents a character by its
 Unicode property `name' or `old-name'.
@@ -3216,7 +3216,10 @@ read-char-by-name
 number like \"2A10\", or a number in hash notation (e.g.,
 \"#x2a10\" for hex, \"10r10768\" for decimal, or \"#o25020\" for
 octal).  Treat otherwise-ambiguous strings like \"BED\" (U+1F6CF)
-as names, not numbers."
+as names, not numbers.
+
+Optional arg ALLOW-SINGLE non-nil means to additionally allow
+single characters to be treated as standing for themselves."
   (let* ((enable-recursive-minibuffers t)
         (completion-ignore-case t)
         (completion-tab-width 4)
@@ -3239,6 +3242,9 @@ read-char-by-name
         (char
           (cond
            ((char-from-name input t))
+           ((and allow-single
+                 (string-match-p "\\`.\\'" input)
+                 (ignore-errors (string-to-char input))))
            ((string-match-p "\\`[[:xdigit:]]+\\'" input)
             (ignore-errors (string-to-number input 16)))
            ((string-match-p "\\`#\\([bBoOxX]\\|[0-9]+[rR]\\)[0-9a-zA-Z]+\\'"

Robert
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