From: Lars Ingebrigtsen <larsi@gnus.org>
Date: Sat, 26 Sep 2020 22:17:58 +0000 (+0200)
Subject: Slight replace-in-string optimization
X-Git-Tag: emacs-28.0.90~5863
X-Git-Url: http://git.eshelyaron.com/gitweb/?a=commitdiff_plain;h=53cf5936c19a6c7352483323666c3915de6f7746;p=emacs.git

Slight replace-in-string optimization

* lisp/subr.el (replace-in-string): Optimize to return the
original string if nothing was replaced (bug#43598).
---

diff --git a/lisp/subr.el b/lisp/subr.el
index dd797021f1c..357eae0f505 100644
--- a/lisp/subr.el
+++ b/lisp/subr.el
@@ -4442,10 +4442,13 @@ Unless optional argument INPLACE is non-nil, return a new string."
         (push (substring instring start pos) result))
       (push tostring result)
       (setq start (+ pos (length fromstring))))
-    ;; Get any remaining bit.
-    (unless (= start (length instring))
-      (push (substring instring start) result))
-    (apply #'concat (nreverse result))))
+    (if (null result)
+        ;; No replacements were done, so just return the original string.
+        instring
+      ;; Get any remaining bit.
+      (unless (= start (length instring))
+        (push (substring instring start) result))
+      (apply #'concat (nreverse result)))))
 
 (defun replace-regexp-in-string (regexp rep string &optional
 					fixedcase literal subexp start)