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* lisp/subr.el (activate-change-group): Refine fix for bug#33341

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This commit is contained in:
Stefan Monnier 2020-11-27 10:19:21 -05:00
parent 8ebf041d5f
commit 1f633311c1
2 changed files with 26 additions and 4 deletions
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15
lisp/subr.el
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@ -3038,8 +3038,19 @@ to `accept-change-group' or `cancel-change-group'."
(if (eq buffer-undo-list t)
(setq buffer-undo-list nil)
;; Add a boundary to make sure the upcoming changes won't be
;; merged with any previous changes (bug#33341).
(undo-boundary)))))
;; merged/combined with any previous changes (bug#33341).
;; We're not supposed to introduce a real (visible)
;; `undo-boundary', tho, so we have to push something else
;; that acts like a boundary w.r.t preventing merges while
;; being harmless.
;; We use for that an "empty insertion", but in order to be harmless,
;; it has to be at a harmless position. Currently only
;; insertions are ever merged/combined, so we use such a "boundary"
;; only when the last change was an insertion and we use the position
;; of the last insertion.
(when (numberp (caar buffer-undo-list))
(push (cons (caar buffer-undo-list) (caar buffer-undo-list))
buffer-undo-list))))))
(defun accept-change-group (handle)
"Finish a change group made with `prepare-change-group' (which see).

15
test/lisp/subr-tests.el
View file

@ -555,13 +555,24 @@ See https://debbugs.gnu.org/cgi/bugreport.cgi?bug=19350."
(with-temp-buffer
(buffer-enable-undo)
(insert "0\n")
;; (undo-boundary)
(let ((g (prepare-change-group)))
(activate-change-group g)
(insert "b\n")
(insert "c\n")
(cancel-change-group g))
(should (equal (buffer-string) "0\n"))))
(should (equal (buffer-string) "0\n"))
(erase-buffer)
(setq buffer-undo-list nil)
(insert "0\n")
(let ((g (prepare-change-group)))
(activate-change-group g)
(insert "b\n")
(insert "c\n")
(accept-change-group g))
(should (equal (buffer-string) "0\nb\nc\n"))
(undo-boundary)
(undo)
(should (equal (buffer-string) ""))))
(provide 'subr-tests)
;;; subr-tests.el ends here