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Re: [Emacs-diffs] master 682ab5d 2/2: Adjust previous electric.el and el
From: |
Stefan Monnier |
Subject: |
Re: [Emacs-diffs] master 682ab5d 2/2: Adjust previous electric.el and elec-pair.el change |
Date: |
Fri, 25 Jan 2019 15:01:33 -0500 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/27.0.50 (gnu/linux) |
> This fixes a serious bug introduced previously
> electric-pair-inhibit-if-helps-balance and
> electric-pair-skip-if-helps-balance, whereby "innocent" markers were
> being pushed by those function's new save-change-and-restore
> semantics. The fix can probably still be improved.
Could you add corresponding test cases?
> + ;; FIXME: need this instead of `save-excursion' when functions in
> + ;; BODY, such as `electric-pair-inhibit-if-helps-balance' and
> + ;; `electric-pair-skip-if-helps-balance' modify and restore the
> + ;; buffer in a way that modifies the marker used by save-excursion.
Then maybe a better approach is to use `undo`, as in the 100% untested
(and guaranteed incomplete) patch below,
Stefan
diff --git a/lisp/elec-pair.el b/lisp/elec-pair.el
index b5ec492930..3be09d87b4 100644
--- a/lisp/elec-pair.el
+++ b/lisp/elec-pair.el
@@ -429,20 +429,25 @@ electric-pair-inhibit-if-helps-balance
happened."
(pcase (electric-pair-syntax-info char)
(`(,syntax ,pair ,_ ,s-or-c)
- (unwind-protect
- (progn
- (delete-char -1)
- (cond ((eq ?\( syntax)
- (let* ((pair-data
- (electric-pair--balance-info 1 s-or-c))
- (outermost (cdr pair-data)))
- (cond ((car outermost)
- nil)
- (t
- (eq (cdr outermost) pair)))))
- ((eq syntax ?\")
- (electric-pair--unbalanced-strings-p char))))
- (insert char)))))
+ (catch 'done
+ ;; FIXME: modify+undo is *very* tricky business. We used to
+ ;; use `delete-char' followed by `insert', but this changed the
+ ;; position of some markers. The real fix would be to compute the
+ ;; result without having to modify the buffer at all.
+ (atomic-change-group
+ (delete-char -1)
+ (throw
+ 'done
+ (cond ((eq ?\( syntax)
+ (let* ((pair-data
+ (electric-pair--balance-info 1 s-or-c))
+ (outermost (cdr pair-data)))
+ (cond ((car outermost)
+ nil)
+ (t
+ (eq (cdr outermost) pair)))))
+ ((eq syntax ?\")
+ (electric-pair--unbalanced-strings-p char)))))))))
(defun electric-pair-skip-if-helps-balance (char)
"Return non-nil if skipping CHAR would benefit parentheses' balance.
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