GNU bug report logs - #42654
Using electric-pair-inihibit-predicate won't work for all members of electric-pair-pairs

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: ej32u <at> protonmail.com
To: "bug-gnu-emacs <at> gnu.org" <bug-gnu-emacs <at> gnu.org>
Subject: Using electric-pair-inihibit-predicate won't work for all members of
 electric-pair-pairs
Date: Sat, 01 Aug 2020 17:31:55 +0000

[Message part 1 (text/plain, inline)]

Hello,

This is what I understood from testing (Emacs 28.0.50) and the code of electric-pair-mode.

- More pairs can be defined by adding to electric-pair-pairs.
- To use electric-pair-inhibit-predicate, the syntax of the character must be one of '(?\( ?\" ?\$).

- In Org mode, it is convenient to have pairs for "~", "+", "_", and "/". These characters are not in the syntax classes required to run the inhibition function.
- The syntax class of the characters can be modified, such as with (modify-syntax-entry ?* "$").

- Once the syntax class is modified, the characters are automatically paired by electric-pair-mode. This means that the characters then do no need to be added to electric-pair-pairs.

I think it is a bug that electric-pair-inhibit-predicate won't be run when checking members of electric-pair-pairs. Yes, the syntax can be modified, but that makes the adding of the pair to electric-pair-pairs redundant, no?

Am I misunderstanding the purpose of these variables?

Thank you.

[Message part 2 (text/html, inline)]

Message #8 received at 42654 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: ej32u <at> protonmail.com
Cc: 42654 <at> debbugs.gnu.org
Subject: Re: bug#42654: Using electric-pair-inihibit-predicate won't work
 for all members of electric-pair-pairs
Date: Mon, 06 Jun 2022 17:28:33 +0200

ej32u <at> protonmail.com writes:

> * More pairs can be defined by adding to electric-pair-pairs.
> * To use electric-pair-inhibit-predicate, the syntax of the character must be one of '
>  (?\( ?\" ?\$).
> * In Org mode, it is convenient to have pairs for "~", "+", "_", and "/". These
>  characters are not in the syntax classes required to run the inhibition function.
> * The syntax class of the characters can be modified, such as with
>  (modify-syntax-entry ?* "$").
> * Once the syntax class is modified, the characters are automatically paired by
>  electric-pair-mode. This means that the characters then do no need to be added to
>  electric-pair-pairs.
>
> I think it is a bug that electric-pair-inhibit-predicate won't be run when checking
> members of electric-pair-pairs. Yes, the syntax can be modified, but that makes the
> adding of the pair to electric-pair-pairs redundant, no?

(I'm going through old bug reports that unfortunately weren't resolved
at the time.)

Looking at the code, I'm not quite sure I understand your point here.
Perhaps it would be easier if you had a simple test case, and you could
explain what you see happening, and what you want to have happen?

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

Message #13 received at 42654 <at> debbugs.gnu.org (full text, mbox):

From: ej32u <at> protonmail.com
To: Lars Ingebrigtsen <larsi <at> gnus.org>
Cc: 42654 <at> debbugs.gnu.org
Subject: Re: bug#42654: Using electric-pair-inihibit-predicate won't work for
 all members of electric-pair-pairs
Date: Tue, 07 Jun 2022 02:08:01 +0000

On 6/6/22 11:28, Lars Ingebrigtsen wrote:
 > (I'm going through old bug reports that unfortunately weren't resolved
 > at the time.)
 >
 > Looking at the code, I'm not quite sure I understand your point here.
 > Perhaps it would be easier if you had a simple test case, and you could
 > explain what you see happening, and what you want to have happen?
 >
 > --
 > (domestic pets only, the antidote for overdose, milk.)
 >    bloggy blog: http://lars.ingebrigtsen.no

Hello,

This was a while ago, but here is how I remember it.  I wanted to add
the character "*" to ~electric-pair-pairs~ for Org mode.  However, I did
not want it to pair when inserting at the beginning of a line, since the
character is also used to begin headings.

I tried setting ~electric-pair-inhibit-predicate~, but found that it
isn't used unless the inserted character has the right syntax. That
function is run by  ~electric-pair-post-self-insert-function~, which
seems to only run the predicate function if the inserted character is
~(memq syntax '(?\( ?\" ?\$))~.

I think that the running of the inhibition function should also occur
for pairs in ~electric-pair-pairs~ and that it should not depend on the
syntax of the inserted character for pairs in ~electric-pair-pairs~.

Nowadays, I am using Smartparens (https://github.com/Fuco1/smartparens),
which already has the behavior I sought.

Below is an example:

1. Add the character "*" to ~electric-pair-pairs~ so that it is
automatically
    paired:

    #+begin_src emacs-lisp
      (setq-local electric-pair-pairs (cons '(?* . ?*) electric-pair-pairs))
    #+end_src

2. Add a predicate to not pair "*" when it is at the beginning of a
    line.  NOTE: This does not work. The character "*" does not have
    the required syntax to run in
    ~electric-pair-post-self-insert-function~ (one of ?\), ?\", or ?\$).

    #+begin_src emacs-lisp
      (defun my-inhibit-for-org-heading (inserted-char)
        (or (and (eq inserted-char ?*)
                 ;; If point was the beginning of the line, don't pair.
                 (eq (1- (point)) (line-beginning-position)))
            (funcall (default-toplevel-value
'electric-pair-inhibit-predicate)
                     inserted-char)))

      (setq-local electric-pair-inhibit-predicate
#'my-inhibit-for-org-heading)
    #+end_src

3. Test inserting "*" at the beginning of the line.  See that it is
    paired.

Message #16 received at 42654 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: ej32u <at> protonmail.com
Cc: 42654 <at> debbugs.gnu.org,
 João Távora <joaotavora <at> gmail.com>
Subject: Re: bug#42654: Using electric-pair-inihibit-predicate won't work
 for all members of electric-pair-pairs
Date: Tue, 07 Jun 2022 11:53:17 +0200

ej32u <at> protonmail.com writes:

> I tried setting ~electric-pair-inhibit-predicate~, but found that it
> isn't used unless the inserted character has the right syntax. That
> function is run by  ~electric-pair-post-self-insert-function~, which
> seems to only run the predicate function if the inserted character is
> ~(memq syntax '(?\( ?\" ?\$))~.

Ah, right.  Here's the complete recipe to reproduce the problem:

(progn
  (require 'elec-pair)

  (setq-local electric-pair-pairs (cons '(?* . ?*) electric-pair-pairs))
  (electric-pair-mode 1)

  (defun my-inhibit-for-org-heading (inserted-char)
    (or (and (eq inserted-char ?*)
             ;; If point was the beginning of the line, don't pair.
             (eq (1- (point)) (line-beginning-position)))
	(funcall (default-toplevel-value
		  'electric-pair-inhibit-predicate)
		 inserted-char)))

  (setq-local electric-pair-inhibit-predicate #'my-inhibit-for-org-heading))

`my-inhibit-for-org-heading' is never run when typing * in this
scenario, because it doesn't have parentheses/quote syntax, so
`electric-pair-syntax-info' returns UNCONDITIONAL true.

I'm not sure what the logic is behind this -- perhaps João has some
comments; added to the CCs.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

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