bug#67390: 28; shorthands-font-lock-shorthands assumes shorthand uses same separator

[Joseph Turner via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

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Jonas Bernoulli <jonas@bernoul.li> writes:

> Joseph Turner <joseph@ushin.org> writes:
>
>> +                          (car (shorthands--find-if
>> +                                (lambda (short)
>> +                                  (string-prefix-p short (match-string 1)))
>> +                                read-symbol-shorthands #'car)))))
>
> Or simply:
>   (car (assoc (match-string 1)
>               read-symbol-shorthands
>               #'string-prefix-p))

Much nicer - see patch.  Thanks, Jonas!


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From 5033a0e14950ed1622db78df1828c40de4b5a23a Mon Sep 17 00:00:00 2001
From: Joseph Turner <joseph@breatheoutbreathe.in>
Date: Fri, 24 Nov 2023 19:17:13 -0800
Subject: [PATCH] Support shorthand prefixes besides "-"

* lisp/emacs-lisp/shorthands.el (shorthands-font-lock-shorthands):
Add font locking to the shorthand prefix by checking if any of the
shorthand prefixes in read-symbol-shorthands are a prefix for the
current symbol name (bug#67390).

Co-authored-by: Jonas Bernoulli <jonas@bernoul.li>
---
 lisp/emacs-lisp/shorthands.el | 19 ++++++++-----------
 1 file changed, 8 insertions(+), 11 deletions(-)

diff --git a/lisp/emacs-lisp/shorthands.el b/lisp/emacs-lisp/shorthands.el
index 82200ab88e9..6ce9984a353 100644
--- a/lisp/emacs-lisp/shorthands.el
+++ b/lisp/emacs-lisp/shorthands.el
@@ -52,13 +52,6 @@
   :version "28.1"
   :group 'font-lock-faces)
 
-(defun shorthands--mismatch-from-end (str1 str2)
-  (cl-loop with l1 = (length str1) with l2 = (length str2)
-           for i from 1
-           for i1 = (- l1 i) for i2 = (- l2 i)
-           while (and (>= i1 0) (>= i2 0) (eq (aref str1 i1) (aref str2 i2)))
-           finally (return (1- i))))
-
 (defun shorthands-font-lock-shorthands (limit)
   (when read-symbol-shorthands
     (while (re-search-forward
@@ -69,10 +62,14 @@
                                                font-lock-string-face)))
                          (intern-soft (match-string 1))))
              (sname (and probe (symbol-name probe)))
-             (mm (and sname (shorthands--mismatch-from-end
-                             (match-string 1) sname))))
-        (unless (or (null mm) (= mm (length sname)))
-          (add-face-text-property (match-beginning 1) (1+ (- (match-end 1) mm))
+             (prefix (and sname
+                          (not (string-equal (match-string 1) sname))
+                          (car (assoc (match-string 1)
+                                      read-symbol-shorthands
+                                      #'string-prefix-p)))))
+        (when prefix
+          (add-face-text-property (match-beginning 1)
+                                  (+ (match-beginning 1) (length prefix))
                                   'elisp-shorthand-font-lock-face))))))
 
 (font-lock-add-keywords 'emacs-lisp-mode '((shorthands-font-lock-shorthands)) t)
-- 
2.41.0