The file is quite short, so in this case is better to get rid of it and just insert its contents into the buffer.
Fix bug#21766 and add test.
* lisp/simple.el (delete-trailing-whitespace): Save match data when
calling `skip-syntax-backward'.
* test/automated/simple-test.el (simple-delete-trailing-whitespace):
New test.
diff --git a/lisp/simple.el b/lisp/simple.el
index 338a060..f6c580f 100644
--- a/lisp/simple.el
+++ b/lisp/simple.el
@@ -609,7 +609,8 @@ delete-trailing-whitespace
(start (or start (point-min))))
(goto-char start)
(while (re-search-forward "\\s-$" end-marker t)
- (skip-syntax-backward "-" (line-beginning-position))
+ (save-match-data
+ (skip-syntax-backward "-" (line-beginning-position)))
;; Don't delete formfeeds, even if they are considered whitespace.
(if (looking-at-p ".*\f")
(goto-char (match-end 0)))
diff --git a/test/automated/simple-test.el b/test/automated/simple-test.el
index 8da575d..5bfb746 100644
--- a/test/automated/simple-test.el
+++ b/test/automated/simple-test.el
@@ -180,5 +180,27 @@ simple-test--dummy-buffer
(should (= x 2)))
(remove-hook 'post-self-insert-hook inc))))
+
+;;; `delete-trailing-whitespace'
+(ert-deftest simple-delete-trailing-whitespace ()
+ "Test bug#21766: delete-whitespace sometimes deletes non-whitespace."
+ (defvar python-indent-guess-indent-offset) ; to avoid a warning
+ (let ((python (featurep 'python))
+ (python-indent-guess-indent-offset nil)
+ (delete-trailing-lines t))
+ (unwind-protect
+ (with-temp-buffer
+ (python-mode)
+ (insert (concat "query = \"\"\"WITH filtered AS \n"
+ "WHERE \n"
+ "\"\"\".format(fv_)\n"
+ "\n"
+ "\n"))
+ (delete-trailing-whitespace)
+ (should (equal (count-lines (point-min) (point-max)) 3)))
+ ;; Let's clean up if running interactive
+ (unless (or noninteractive python)
+ (unload-feature 'python)))))
+
(provide 'simple-test)
;;; simple-test.el ends here
--
2.6.2.windows.1