bug#72437: Unexpected behavior when inserting with prefix arg in electric-pair-mode

bug#72437: Unexpected behavior when inserting with prefix arg in electric-pair-mode

[Joseph Turner via Bug reports for GNU Emacs, the Swiss army knife of text editors]

Migrated from this thread on the devel mailing list:

https://yhetil.org/emacs-devel/86ikwiumza.fsf@gnu.org/T/#t


On Emacs 29.4, with emacs -Q

Turn on electric-pair-mode

(electric-pair-mode +1)

Then press "C-2 ("

Expected result:

Either (()) or ()()

Actual result:

(()


I noticed the unexpected behavior when attempting to surround some text
with multiple braces in order to create Anki flashcards.

More or less, I wanted to go from "foo" to "{{foo}}", and I thought
perhaps that with the whole word selected, pressing "C-2 {" would DTRT.

In general, I'm not sure whether "{}{}" or "{{}}"is more useful or
expected, but I suspect both are better than "{{}".

Thank you!

Joseph

bug#72437: Unexpected behavior when inserting with prefix arg in electric-pair-mode

[Eli Zaretskii]

> Cc: eliz@gnu.org
> From: Joseph Turner <joseph@breatheoutbreathe.in>
> Date: Sat, 03 Aug 2024 00:12:33 -0700
> 
> Migrated from this thread on the devel mailing list:
> 
> https://yhetil.org/emacs-devel/86ikwiumza.fsf@gnu.org/T/#t
> 
> 
> On Emacs 29.4, with emacs -Q
> 
> Turn on electric-pair-mode
> 
> (electric-pair-mode +1)
> 
> Then press "C-2 ("
> 
> Expected result:
> 
> Either (()) or ()()
> 
> Actual result:
> 
> (()
> 
> 
> I noticed the unexpected behavior when attempting to surround some text
> with multiple braces in order to create Anki flashcards.
> 
> More or less, I wanted to go from "foo" to "{{foo}}", and I thought
> perhaps that with the whole word selected, pressing "C-2 {" would DTRT.
> 
> In general, I'm not sure whether "{}{}" or "{{}}"is more useful or
> expected, but I suspect both are better than "{{}".

Making it produce "{}{}" is relatively easy: we just need to call the
post-self-insert-hook for each of the ARG inserted characters.  OTOH,
to produce "{{}}" we'd probably need to rewrite the
electric-pair-mode's hook function, but I have no idea how to rewrite
it to do that.

Stefan, any suggestions?

bug#72437: Unexpected behavior when inserting with prefix arg in electric-pair-mode

[Eshel Yaron via Bug reports for GNU Emacs, the Swiss army knife of text editors]

Eli Zaretskii <eliz@gnu.org> writes:

>> Cc: eliz@gnu.org
>> From: Joseph Turner <joseph@breatheoutbreathe.in>
>> Date: Sat, 03 Aug 2024 00:12:33 -0700
>> 
>> Migrated from this thread on the devel mailing list:
>> 
>> https://yhetil.org/emacs-devel/86ikwiumza.fsf@gnu.org/T/#t
>> 
>> 
>> On Emacs 29.4, with emacs -Q
>> 
>> Turn on electric-pair-mode
>> 
>> (electric-pair-mode +1)
>> 
>> Then press "C-2 ("
>> 
>> Expected result:
>> 
>> Either (()) or ()()
>> 
>> Actual result:
>> 
>> (()
>> 
>> 
>> I noticed the unexpected behavior when attempting to surround some text
>> with multiple braces in order to create Anki flashcards.
>> 
>> More or less, I wanted to go from "foo" to "{{foo}}", and I thought
>> perhaps that with the whole word selected, pressing "C-2 {" would DTRT.
>> 
>> In general, I'm not sure whether "{}{}" or "{{}}"is more useful or
>> expected, but I suspect both are better than "{{}".
>
> Making it produce "{}{}" is relatively easy: we just need to call the
> post-self-insert-hook for each of the ARG inserted characters.  OTOH,
> to produce "{{}}" we'd probably need to rewrite the
> electric-pair-mode's hook function, but I have no idea how to rewrite
> it to do that.
>
> Stefan, any suggestions?

I'm no Stefan, but I took a quick stab at it.  The following diff
teaches electric-pair-mode about numeric prefix arguments:

diff --git a/lisp/elec-pair.el b/lisp/elec-pair.el
index 40618e9ef38..1fae0ba6ba4 100644
--- a/lisp/elec-pair.el
+++ b/lisp/elec-pair.el
@@ -260,7 +260,7 @@ electric-pair-syntax-info
                (list ?\( (cdr direct) t string-or-comment)))
      (reverse (list ?\) (car reverse) t string-or-comment)))))
 
-(defun electric-pair--insert (char)
+(defun electric-pair--insert (char times)
   (let ((last-command-event char)
 	(blink-matching-paren nil)
 	(electric-pair-mode nil)
@@ -271,7 +271,7 @@ electric-pair--insert
         ;; us to add these newlines, and is probably about to kick in
         ;; again after we add the closer.
         (electric-layout-allow-duplicate-newlines t))
-    (self-insert-command 1)))
+    (self-insert-command times)))
 
 (defun electric-pair--syntax-ppss (&optional pos where)
   "Like `syntax-ppss', but sometimes fallback to `parse-partial-sexp'.
@@ -455,7 +455,8 @@ electric-pair-inhibit-if-helps-balance
        (atomic-change-group
          ;; Don't use `delete-char'; that may modify the head of the
          ;; undo list.
-         (delete-region (point) (1- (point)))
+         (delete-region (- (point) (prefix-numeric-value current-prefix-arg))
+                        (point))
          (throw
           'done
           (cond ((eq ?\( syntax)
@@ -474,25 +475,26 @@ electric-pair-skip-if-helps-balance
 Works by first removing the character from the buffer, then doing
 some list calculations, finally restoring the situation as if nothing
 happened."
-  (pcase (electric-pair-syntax-info char)
-    (`(,syntax ,pair ,_ ,s-or-c)
-     (unwind-protect
-         (progn
-           (delete-char -1)
-           (cond ((eq syntax ?\))
-                  (let* ((pair-data
-                          (electric-pair--balance-info
-                           -1 s-or-c))
-                         (innermost (car pair-data))
-                         (outermost (cdr pair-data)))
-                    (and
-                     (cond ((car outermost)
-                            (car innermost))
-                           ((car innermost)
-                            (not (eq (cdr outermost) pair)))))))
-                 ((eq syntax ?\")
-                  (electric-pair--inside-string-p char))))
-       (insert char)))))
+  (let ((num (prefix-numeric-value current-prefix-arg)))
+    (pcase (electric-pair-syntax-info char)
+      (`(,syntax ,pair ,_ ,s-or-c)
+       (unwind-protect
+           (progn
+             (delete-char (- num))
+             (cond ((eq syntax ?\))
+                    (let* ((pair-data
+                            (electric-pair--balance-info
+                             (- num) s-or-c))
+                           (innermost (car pair-data))
+                           (outermost (cdr pair-data)))
+                      (and
+                       (cond ((car outermost)
+                              (car innermost))
+                             ((car innermost)
+                              (not (eq (cdr outermost) pair)))))))
+                   ((eq syntax ?\")
+                    (electric-pair--inside-string-p char))))
+         (insert (make-string num char)))))))
 
 (defun electric-pair-default-skip-self (char)
   (if electric-pair-preserve-balance
@@ -527,11 +529,14 @@ electric-pair-post-self-insert-function
  `electric-pair-inhibit-predicate', `electric-pair-skip-self'
   and `electric-pair-skip-whitespace' (which see)."
   (let* ((pos (and electric-pair-mode (electric--after-char-pos)))
+         (num (when pos (prefix-numeric-value current-prefix-arg)))
+         (beg (when num (- pos num)))
          (skip-whitespace-info))
     (pcase (electric-pair-syntax-info last-command-event)
       (`(,syntax ,pair ,unconditional ,_)
        (cond
         ((null pos) nil)
+        ((zerop num) nil)
         ;; Wrap a pair around the active region.
         ;;
         ((and (memq syntax '(?\( ?\) ?\" ?\$)) (use-region-p))
@@ -545,23 +550,24 @@ electric-pair-post-self-insert-function
                       (>= (mark) (point))))
              (save-excursion
                (goto-char (mark))
-               (electric-pair--insert pair))
-           (delete-region pos (1- pos))
-           (electric-pair--insert pair)
+               (electric-pair--insert pair num))
+           (delete-region beg pos)
+           (electric-pair--insert pair num)
            (goto-char (mark))
-           (electric-pair--insert last-command-event)))
+           (electric-pair--insert last-command-event num)))
         ;; Backslash-escaped: no pairing, no skipping.
         ((save-excursion
-           (goto-char (1- pos))
+           (goto-char beg)
            (not (zerop (% (skip-syntax-backward "\\") 2))))
-         nil)
+         (let ((current-prefix-arg (1- num)))
+           (electric-pair-post-self-insert-function)))
         ;; Skip self.
         ((and (memq syntax '(?\) ?\" ?\$))
               (and (or unconditional
                        (if (functionp electric-pair-skip-self)
                            (electric-pair--save-literal-point-excursion
-                             (goto-char pos)
-                             (funcall electric-pair-skip-self last-command-event))
+                            (goto-char pos)
+                            (funcall electric-pair-skip-self last-command-event))
                          electric-pair-skip-self))
                    (save-excursion
                      (when (and (not (and unconditional
@@ -580,19 +586,19 @@ electric-pair-post-self-insert-function
          ;; live with it for now.
          (when skip-whitespace-info
            (funcall electric-pair-skip-whitespace-function))
-         (delete-region (1- pos) (if (eq skip-whitespace-info 'chomp)
-                                     (point)
-                                   pos))
-         (forward-char))
+         (delete-region beg (if (eq skip-whitespace-info 'chomp)
+                                (point)
+                              pos))
+         (forward-char num))
         ;; Insert matching pair.
         ((and (memq syntax '(?\( ?\" ?\$))
               (not overwrite-mode)
               (or unconditional
                   (not (electric-pair--save-literal-point-excursion
-                         (goto-char pos)
-                         (funcall electric-pair-inhibit-predicate
-                                  last-command-event)))))
-         (save-excursion (electric-pair--insert pair))))))))
+                        (goto-char pos)
+                        (funcall electric-pair-inhibit-predicate
+                                 last-command-event)))))
+         (save-excursion (electric-pair--insert pair num))))))))
 
 (defun electric-pair-open-newline-between-pairs-psif ()
   "Honor `electric-pair-open-newline-between-pairs'.
@@ -604,7 +610,8 @@ electric-pair-open-newline-between-pairs-psif
              (< (1+ (point-min)) (point) (point-max))
              (eq (save-excursion
                    (skip-chars-backward "\t\s")
-                   (char-before (1- (point))))
+                   (char-before (- (point)
+                                   (prefix-numeric-value current-prefix-arg))))
                  (matching-paren (char-after))))
     (save-excursion (newline 1 t))))
 
@@ -618,7 +625,7 @@ electric-pair-delete-pair
 ARG and KILLP are passed directly to
 `backward-delete-char-untabify', which see."
   (interactive "*p\nP")
-  (delete-char 1)
+  (delete-char arg)
   (backward-delete-char-untabify arg killp))
 
 (defvar electric-pair-mode-map

bug#72437: Unexpected behavior when inserting with prefix arg in electric-pair-mode

[Eli Zaretskii]

> From: Eshel Yaron <me@eshelyaron.com>
> Cc: Joseph Turner <joseph@breatheoutbreathe.in>,  Stefan Monnier
>  <monnier@iro.umontreal.ca>,  72437@debbugs.gnu.org
> Date: Sat, 03 Aug 2024 13:04:58 +0200
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > post-self-insert-hook for each of the ARG inserted characters.  OTOH,
> > to produce "{{}}" we'd probably need to rewrite the
> > electric-pair-mode's hook function, but I have no idea how to rewrite
> > it to do that.
> >
> > Stefan, any suggestions?
> 
> I'm no Stefan, but I took a quick stab at it.  The following diff
> teaches electric-pair-mode about numeric prefix arguments:

Thanks, but isn't it cleaner if we simply call the hook from cmds.c
the same number of times as we insert a character?

bug#72437: Unexpected behavior when inserting with prefix arg in electric-pair-mode

[Eshel Yaron via Bug reports for GNU Emacs, the Swiss army knife of text editors]

Hi Eli,

Eli Zaretskii <eliz@gnu.org> writes:

>> From: Eshel Yaron <me@eshelyaron.com>
>> Cc: Joseph Turner <joseph@breatheoutbreathe.in>,  Stefan Monnier
>>  <monnier@iro.umontreal.ca>,  72437@debbugs.gnu.org
>> Date: Sat, 03 Aug 2024 13:04:58 +0200
>> 
>> Eli Zaretskii <eliz@gnu.org> writes:
>> 
>> > post-self-insert-hook for each of the ARG inserted characters.  OTOH,
>> > to produce "{{}}" we'd probably need to rewrite the
>> > electric-pair-mode's hook function, but I have no idea how to rewrite
>> > it to do that.
>> >
>> > Stefan, any suggestions?
>> 
>> I'm no Stefan, but I took a quick stab at it.  The following diff
>> teaches electric-pair-mode about numeric prefix arguments:
>
> Thanks, but isn't it cleaner if we simply call the hook from cmds.c
> the same number of times as we insert a character?

Interesting, it might work for electric-pair-mode, though I suspect that
not all functions that people put on post-self-insert-hook are prepared
to be invoked repeatedly following a single self-insert-command.

bug#72437: Unexpected behavior when inserting with prefix arg in electric-pair-mode

[Eli Zaretskii]

> From: Eshel Yaron <me@eshelyaron.com>
> Cc: joseph@breatheoutbreathe.in,  monnier@iro.umontreal.ca,
>   72437@debbugs.gnu.org
> Date: Sat, 03 Aug 2024 20:18:06 +0200
> 
> >> I'm no Stefan, but I took a quick stab at it.  The following diff
> >> teaches electric-pair-mode about numeric prefix arguments:
> >
> > Thanks, but isn't it cleaner if we simply call the hook from cmds.c
> > the same number of times as we insert a character?
> 
> Interesting, it might work for electric-pair-mode, though I suspect that
> not all functions that people put on post-self-insert-hook are prepared
> to be invoked repeatedly following a single self-insert-command.

It isn't a single self-insert-command, since it inserts N characters.
So it is natural to expect the hook to be invoked those same N times.
I think.  Let's hear what Stefan thinks (and anyone else who has an
opinion or some case other than electric-pair-mode).

bug#72437: Unexpected behavior when inserting with prefix arg in electric-pair-mode

[Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors]

Hi João,

Do you have a good idea of how to make

   C-M-SPC C-2 {

wrap the selected word within two braces?


        Stefan


Eli Zaretskii [2024-08-03 12:12:06] wrote:

>> Cc: eliz@gnu.org
>> From: Joseph Turner <joseph@breatheoutbreathe.in>
>> Date: Sat, 03 Aug 2024 00:12:33 -0700
>> 
>> Migrated from this thread on the devel mailing list:
>> 
>> https://yhetil.org/emacs-devel/86ikwiumza.fsf@gnu.org/T/#t
>> 
>> 
>> On Emacs 29.4, with emacs -Q
>> 
>> Turn on electric-pair-mode
>> 
>> (electric-pair-mode +1)
>> 
>> Then press "C-2 ("
>> 
>> Expected result:
>> 
>> Either (()) or ()()
>> 
>> Actual result:
>> 
>> (()
>> 
>> 
>> I noticed the unexpected behavior when attempting to surround some text
>> with multiple braces in order to create Anki flashcards.
>> 
>> More or less, I wanted to go from "foo" to "{{foo}}", and I thought
>> perhaps that with the whole word selected, pressing "C-2 {" would DTRT.
>> 
>> In general, I'm not sure whether "{}{}" or "{{}}"is more useful or
>> expected, but I suspect both are better than "{{}".
>
> Making it produce "{}{}" is relatively easy: we just need to call the
> post-self-insert-hook for each of the ARG inserted characters.  OTOH,
> to produce "{{}}" we'd probably need to rewrite the
> electric-pair-mode's hook function, but I have no idea how to rewrite
> it to do that.
>
> Stefan, any suggestions?

bug#72437: Unexpected behavior when inserting with prefix arg in electric-pair-mode

[Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors]

> It isn't a single self-insert-command, since it inserts N characters.
> So it is natural to expect the hook to be invoked those same N times.
> I think.  Let's hear what Stefan thinks (and anyone else who has an
> opinion or some case other than electric-pair-mode).

I think the requested behavior makes a lot of sense, but I lost touch
with the way elec-pair works and interacts with other electric modes, so
I'm not sure how to make it work without breaking other things.


        Stefan

bug#72437: Unexpected behavior when inserting with prefix arg in electric-pair-mode

[Eshel Yaron via Bug reports for GNU Emacs, the Swiss army knife of text editors]

Hi Stefan,

Stefan Monnier writes:

>> Let's hear what Stefan thinks (and anyone else who has an
>> opinion or some case other than electric-pair-mode).
>
> I think the requested behavior makes a lot of sense, but I lost touch
> with the way elec-pair works and interacts with other electric modes, so
> I'm not sure how to make it work without breaking other things.

In case you missed it, the patch I shared upthread might give you
some ideas.  It implements the requested behavior, safely, I think.
So I would just ask Joseph to try it out for a while and see if it
works as expected and if any other issues crop up :)


Cheers,

Eshel

bug#72437: Unexpected behavior when inserting with prefix arg in electric-pair-mode

[Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors]

> In case you missed it, the patch I shared upthread might give you
> some ideas.  It implements the requested behavior, safely, I think.
> So I would just ask Joseph to try it out for a while and see if it
> works as expected and if any other issues crop up :)

I missed that, indeed, sorry.  Then maybe we should just push it to
`master` (with appropriate regression test(s)).


        Stefan

bug#72437: Unexpected behavior when inserting with prefix arg in electric-pair-mode

[João Távora]

[-- Attachment #1: Type: text/plain, Size: 418 bytes --]

On Wed, Aug 14, 2024, 01:57 Stefan Monnier <monnier@iro.umontreal.ca> wrote:

> Hi João,
>
> Do you have a good idea of how to make
>
>    C-M-SPC C-2 {
>
> wrap the selected word within two braces?
>

No great ideas no. Does it even work in the non-wrapping case? The intended
result is as if the command was run twice, no? So maybe try somehow that
the whole thing is run twice/thrice/etc...

João

[-- Attachment #2: Type: text/html, Size: 868 bytes --]

bug#72437: Unexpected behavior when inserting with prefix arg in electric-pair-mode

[Eli Zaretskii]

> Cc: 72437@debbugs.gnu.org, Joseph Turner <joseph@breatheoutbreathe.in>
> From: João Távora <joaotavora@gmail.com>
> Date: Fri, 16 Aug 2024 22:22:29 +0100
> 
> On Wed, Aug 14, 2024, 01:57 Stefan Monnier <monnier@iro.umontreal.ca> wrote:
> 
>  Hi João,
> 
>  Do you have a good idea of how to make
> 
>     C-M-SPC C-2 {
> 
>  wrap the selected word within two braces?
> 
> No great ideas no. Does it even work in the non-wrapping case? The intended result is as if the command was
> run twice, no? So maybe try somehow that the whole thing is run twice/thrice/etc...

That's what I suggested, but the result is "{}{}{}{}...", which is not
what was requested.  IOW, what is being requested is NOT what happens
when running this command N times, it should be a special handling of
the numerical argument.

bug#72437: Unexpected behavior when inserting with prefix arg in electric-pair-mode

[Joseph Turner via Bug reports for GNU Emacs, the Swiss army knife of text editors]

On August 13, 2024 10:07:23 PM PDT, Eshel Yaron <me@eshelyaron.com> wrote:
>Hi Stefan,
>
>Stefan Monnier writes:
>
>>> Let's hear what Stefan thinks (and anyone else who has an
>>> opinion or some case other than electric-pair-mode).
>>
>> I think the requested behavior makes a lot of sense, but I lost touch
>> with the way elec-pair works and interacts with other electric modes, so
>> I'm not sure how to make it work without breaking other things.
>
>In case you missed it, the patch I shared upthread might give you
>some ideas.  It implements the requested behavior, safely, I think.
>So I would just ask Joseph to try it out for a while and see if it
>works as expected and if any other issues crop up :)

Thanks for this patch!  I am testing it in my daily config.  So far so good, and I'll report back after a few weeks of usage.

Warmly,

Joseph

bug#72437: Unexpected behavior when inserting with prefix arg in electric-pair-mode

[João Távora]

On Sat, Aug 17, 2024 at 7:08 AM Eli Zaretskii <eliz@gnu.org> wrote:

> That's what I suggested, but the result is "{}{}{}{}...", which is not
> what was requested.

If the preconditions are that a word is selected before each command,
I don't see how that can be.  At the very least it would be {word}{}{}{}
or something like that.  But if you arrange for word to stay selected and
point before it, I don't see why {{{{word}}}} can't be achieved.  Doesn't
have to be word at all, could be an arbitrary sexp, IIRC. Anyway,
that's all I have.

bug#72437: Unexpected behavior when inserting with prefix arg in electric-pair-mode

[Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors]

> That's what I suggested, but the result is "{}{}{}{}...", which is not

For me `C-u 2 (` results in `(()`.


        Stefan

bug#72437: Unexpected behavior when inserting with prefix arg in electric-pair-mode

[Eli Zaretskii]

> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Cc: João Távora <joaotavora@gmail.com>,
>   72437@debbugs.gnu.org,
>   joseph@breatheoutbreathe.in
> Date: Sat, 17 Aug 2024 10:03:38 -0400
> 
> > That's what I suggested, but the result is "{}{}{}{}...", which is not
> 
> For me `C-u 2 (` results in `(()`.

I suggested a change which would yield ()().  Without the change, you
shouldn't expect getting anything useful, because the hook is called
just once, not ARG times.