Tweak subr-x.el substring functions

* lisp/emacs-lisp/subr-x.el (string-join): #'-quote function symbol.
(string-trim-left, string-trim-right):
Make better use of substring for minor speedup.
* test/lisp/emacs-lisp/subr-x-tests.el
(subr-x-test-string-trim-left, subr-x-test-string-trim-right)
(subr-x-test-string-remove-prefix)
(subr-x-test-string-remove-suffix): New tests.

2 files changed, 53 insertions, 6 deletions

diff --git a/lisp/emacs-lisp/subr-x.el b/lisp/emacs-lisp/subr-x.el
index e03a81c892a..20eb0d5d05c 100644
--- a/lisp/emacs-lisp/subr-x.el
+++ b/lisp/emacs-lisp/subr-x.el
@@ -211,7 +211,7 @@ The variable list SPEC is the same as in `if-let'."
 
 (defsubst string-join (strings &optional separator)
   "Join all STRINGS using SEPARATOR."
-  (mapconcat 'identity strings separator))
+  (mapconcat #'identity strings separator))
 
 (define-obsolete-function-alias 'string-reverse 'reverse "25.1")
 
@@ -219,17 +219,17 @@ The variable list SPEC is the same as in `if-let'."
   "Trim STRING of leading string matching REGEXP.
 
 REGEXP defaults to \"[ \\t\\n\\r]+\"."
-  (if (string-match (concat "\\`\\(?:" (or  regexp "[ \t\n\r]+")"\\)") string)
-      (replace-match "" t t string)
+  (if (string-match (concat "\\`\\(?:" (or regexp "[ \t\n\r]+") "\\)") string)
+      (substring string (match-end 0))
     string))
 
 (defsubst string-trim-right (string &optional regexp)
   "Trim STRING of trailing string matching REGEXP.
 
 REGEXP defaults to  \"[ \\t\\n\\r]+\"."
-  (if (string-match (concat "\\(?:" (or regexp "[ \t\n\r]+") "\\)\\'") string)
-      (replace-match "" t t string)
-    string))
+  (let ((i (string-match-p (concat "\\(?:" (or regexp "[ \t\n\r]+") "\\)\\'")
+                           string)))
+    (if i (substring string 0 i) string)))
 
 (defsubst string-trim (string &optional trim-left trim-right)
   "Trim STRING of leading and trailing strings matching TRIM-LEFT and TRIM-RIGHT.
diff --git a/test/lisp/emacs-lisp/subr-x-tests.el b/test/lisp/emacs-lisp/subr-x-tests.el
index f7f0ef384f6..81467bab2d4 100644
--- a/test/lisp/emacs-lisp/subr-x-tests.el
+++ b/test/lisp/emacs-lisp/subr-x-tests.el
@@ -532,6 +532,53 @@
                    (format "abs sum is: %s"))
                  "abs sum is: 15")))
 
+
+;; Substring tests
+
+(ert-deftest subr-x-test-string-trim-left ()
+  "Test `string-trim-left' behavior."
+  (should (equal (string-trim-left "") ""))
+  (should (equal (string-trim-left " \t\n\r") ""))
+  (should (equal (string-trim-left " \t\n\ra") "a"))
+  (should (equal (string-trim-left "a \t\n\r") "a \t\n\r"))
+  (should (equal (string-trim-left "" "") ""))
+  (should (equal (string-trim-left "a" "") "a"))
+  (should (equal (string-trim-left "aa" "a*") ""))
+  (should (equal (string-trim-left "ba" "a*") "ba"))
+  (should (equal (string-trim-left "aa" "a*?") "aa"))
+  (should (equal (string-trim-left "aa" "a+?") "a")))
+
+(ert-deftest subr-x-test-string-trim-right ()
+  "Test `string-trim-right' behavior."
+  (should (equal (string-trim-right "") ""))
+  (should (equal (string-trim-right " \t\n\r") ""))
+  (should (equal (string-trim-right " \t\n\ra") " \t\n\ra"))
+  (should (equal (string-trim-right "a \t\n\r") "a"))
+  (should (equal (string-trim-right "" "") ""))
+  (should (equal (string-trim-right "a" "") "a"))
+  (should (equal (string-trim-right "aa" "a*") ""))
+  (should (equal (string-trim-right "ab" "a*") "ab"))
+  (should (equal (string-trim-right "aa" "a*?") "")))
+
+(ert-deftest subr-x-test-string-remove-prefix ()
+  "Test `string-remove-prefix' behavior."
+  (should (equal (string-remove-prefix "" "") ""))
+  (should (equal (string-remove-prefix "" "a") "a"))
+  (should (equal (string-remove-prefix "a" "") ""))
+  (should (equal (string-remove-prefix "a" "b") "b"))
+  (should (equal (string-remove-prefix "a" "a") ""))
+  (should (equal (string-remove-prefix "a" "aa") "a"))
+  (should (equal (string-remove-prefix "a" "ab") "b")))
+
+(ert-deftest subr-x-test-string-remove-suffix ()
+  "Test `string-remove-suffix' behavior."
+  (should (equal (string-remove-suffix "" "") ""))
+  (should (equal (string-remove-suffix "" "a") "a"))
+  (should (equal (string-remove-suffix "a" "") ""))
+  (should (equal (string-remove-suffix "a" "b") "b"))
+  (should (equal (string-remove-suffix "a" "a") ""))
+  (should (equal (string-remove-suffix "a" "aa") "a"))
+  (should (equal (string-remove-suffix "a" "ba") "b")))
 
 (provide 'subr-x-tests)
 ;;; subr-x-tests.el ends here