Subject: Re: bug#33794: 26.1; electric-pair-mode breaks auto-newline minor mode of cc-mode

From: João Távora <[email-masked]>
Date: Sat, 22 Dec 2018 01:08:54 +0000

Beatrix Klebe <[email-masked]> writes:

> I know how to do hotpaches but that doesn't appear to solve the
> problem I'm having here, unless I've missed something. The problem is
> with moving the opening bracket, not the insertion point.

Beatrix,

I think you may have missed the fact that I am suggesting alternatives
that:

* involve cc-mode, or one of its derived modes;

* don't involve M-x c-toggle-auto-newline (turning on what you call
  auto-newline-mode);

* involve turning on the global electric-layout-mode and a thin
  customization for it in the buffers where you think it's relevant
  (presumably cc-mode);

* may involve multiple fixed/patched versions of lisp/electric.el as I
  understand your problem(s);

As it stands, the last patch I sent you passes my only test which is
this:  given a file 33794.el which is just:

   (electric-pair-mode)
   (electric-layout-mode)
    
   (add-hook 'c-mode-hook
             (lambda ()
               (setq-local electric-layout-rules
                           '((?\{ . after)
                             (?\{ . after-stay)))))

then running this from a shell:

   $ emacs -Q -l 33794.el something.c

Opens a new c-mode buffer.  Type 'int main ()' and then an opening
brace.  You should get:

   int main () {
       <cursor>
   }

Can you reproduce these results?  If you can come up with more of these
tests written in this or a similarly simple and exact manner it's easier
for me to understand what's going on (it's also easier to write
automated tests).

João

>
>
> On Fri, Dec 21, 2018 at 2:20 PM João Távora <[email-masked]> wrote:
>>
>> Hi Beatrix,
>>
>> The solution I propose involves introducing the hotpatch I attached
>> to fix electric-layout-mode in your emacs, so I wouldn't expect it
>> to work if you haven't done that.
>>
>> Do you know how to do it?
>>
>> Though Alan will probably suggest otherwise, I'd also steer away
>> from c-specific functionality and keep to the triad
>> electric-indent-mode, electric-pair-mode and electric-indent-mode,
>> at least while we try to extend/fix these modes to accommodate your
>> needs.
>>
>> After such a solution is evaluated, you can select to keep it or move to something else.
>>
>> João
>>
>> On Fri, Dec 21, 2018, 19:06 Beatrix Klebe <[email-masked] wrote:
>>>
>>> Here's the link, I believe it was Stefan that answered it:
>>> https://emacs.stackexchange.com/questions/2837/automatically-formatting-brackets/2853#2853
>>>
>>> I have tried this with emacs -Q and it does not fix the issue, which
>>> is as follows.
>>>
>>> Ordinarily in cc-mode when you have auto-newline-mode activated, and
>>> as far as I can tell, a cc-mode configuration that supports it, (which
>>> csharp-mode contains), the following happens when opening a block
>>> (pipe is the cursor):
>>>
>>> void Main() {| // opening bracket is typed
>>>
>>> becomes
>>>
>>> void Main
>>> {
>>>     |
>>>
>>> when c-toggle-auto-newline is activated. However, if you also want
>>> your braces automatically paired, with electric-pair-mode, instead the
>>> following occurs:
>>>
>>> void Main() {| // opening bracket is typed
>>>
>>> void Main() {|} // electric-pair-mode closes the open bracket, but
>>> auto-newline-mode does not appear to do anything.
>>>
>>> void Main() {
>>>     |
>>> } // user hits return, inserting the cursor at the correct indent
>>> level, but leaving the opening brace where it is.
>>>
>>> The ideal/desired behavior is:
>>>
>>> void Main() {| // opening bracket is typed
>>>
>>> void Main()
>>> {
>>>     |
>>> } // user hits return key, electric-pair-mode pairs up the brackets,
>>> and auto-newline-mode formats the braces correctly
>>>
>>> It would also probably suffice to format with the newline before
>>> hitting enter as well, although I think I prefer hitting enter to open
>>> the block. I'm quite curious as to the internals of these formatting
>>> systems and would be happy to help with a fix/feature if that would be
>>> desired, I am mostly an OCaml programmer but C# is my day job and I've
>>> just recently gotten deeper into Emacs Lisp.
>>>
>>> On Fri, Dec 21, 2018 at 1:49 PM João Távora <[email-masked]> wrote:
>>> >
>>> > Beatrix Klebe <[email-masked]> writes:
>>> >
>>> > > I believe I saw your Stack Overflow answer about this while searching
>>> > > for the solution. electric-layout-mode works with some quirks, such as
>>> > > that if you put a space after parens in a function definition, the
>>> > > space gets carried on to the newline with that method, which is a bit
>>> > > annoying. What would be ideal, and what I'm looking for, is to get
>>> > > auto-pairing of brackets with braces being placed where they should be
>>> > > automatically and the insertion point getting put in between them at
>>> > > the correct indent level, such as what happens with Visual Studio, or
>>> > > Visual Studio Code, or several other editors with this functionality.
>>> > > Perhaps it is not emacslike to have such behavior be totally
>>> > > automated, but I am used to it and finds it decreases my ordinary
>>> > > levels of frustration when working with verbose and imperative
>>> > > languages. I am currently trying to write some insert specifiers for
>>> > > smartparens to do this, but it is proving more difficult to find an
>>> > > elegant solution than I had expected.
>>> >
>>> > It is quite emacslike (though maybe not activated by default): you just
>>> > have to report the bugs to the Emacs developers as efficiently as
>>> > possible.
>>> >
>>> > 1. Though Alan possibly has already, I still cannot understand the
>>> >    original problem.  Can you start by describing what the buffer looked
>>> >    like before, what you did, what it looked like afterwards, and what
>>> >    you expected it to look like?  If possible start with a clean Emacs
>>> >    -Q recpe.
>>> >
>>> > 2. I have experimented with nicer-playing like alternatives like
>>> >    electric-layout-mode.  I came across a few quirks myself (though I'm
>>> >    not sure if they are the same as yours). So I prepared a patch (in
>>> >    branch scratch/fix-33794-extend-electric-layout-mode) and attached
>>> >    it after the sig.
>>> >
>>> > After loading this patch, in a simple Emacs -Q the configuration:
>>> >
>>> >    (electric-pair-mode)
>>> >    (electric-layout-mode)
>>> >
>>> >    (add-hook 'c-mode-hook
>>> >           (lambda ()
>>> >             (setq-local electric-layout-rules
>>> >                         '((?\{ . after)
>>> >                           (?\{ . after-stay)))))
>>> >
>>> > And, when visiting a C file, if I press `{' I get the expected
>>> > pair+layout+indent behaviour.  Sor example opening a brace after
>>> > int main () gives me:
>>> >
>>> >     int main () {
>>> >         <cursor here>
>>> >     }
>>> >
>>> > I, like Stefan, think cc-mode could/should set electric-layout-rules
>>> > buffer-locally to reflect whatever c-style the user has selected.
>>> >
>>> > Thanks,
>>> > João
>>> >
>>> > PS: Also, can you link to the the relevant to the stack overflow answer you
>>> > mentioned?
>>> >
>>> > commit ab036bdedbb49ecc96d550b5e883e43bb03eaccc
>>> > Author: JoÃ£o TÃ¡vora <[email-masked]>
>>> > Date:   Fri Dec 21 18:00:08 2018 +0000
>>> >
>>> >     Extend electric-layout-mode to handle more complex layouts
>>> >
>>> >     Also, have it play nice with electric-pair-mode.
>>> >
>>> >     Multiple matching entries in `electric-layout-rules' are executed in
>>> >     order of appearance.  When inserting a newline in the 'after-stay
>>> >     rule, ensure electric-pair-open-newline-between-pairs is nil.
>>> >
>>> >     Arguably the logic behind electric-pair-open-newline-between-pairs
>>> >     should be moved to electric-layout-mode, but the current rule-matching
>>> >     engine doesn't allow for it.  The current solution seems to be good
>>> >     enough for the situations reported in bug#33794.
>>> >
>>> >     * lisp/electric.el (electric-layout-rules): Adjust docstring.
>>> >     (electric-layout-post-self-insert-function): Loop through rules.  Bind
>>> >     electric-pair-open-newline-between-pairs to nil when handling
>>> >     after-stay.
>>> >
>>> > diff --git a/lisp/electric.el b/lisp/electric.el
>>> > index 6dbf46b80c..6a307a49b9 100644
>>> > --- a/lisp/electric.el
>>> > +++ b/lisp/electric.el
>>> > @@ -370,38 +370,43 @@ electric-layout-rules
>>> >
>>> >  The symbols specify where in relation to CHAR the newline
>>> >  character(s) should be inserted. `after-stay' means insert a
>>> > -newline after CHAR but stay in the same place.")
>>> > +newline after CHAR but stay in the same place.
>>> > +
>>> > +If multiple rules match, they are all executed in order of
>>> > +appearance.")
>>> >
>>> >  (defun electric-layout-post-self-insert-function ()
>>> > -  (let* ((rule (cdr (assq last-command-event electric-layout-rules)))
>>> > -         pos)
>>> > -    (when (and rule
>>> > -               (setq pos (electric--after-char-pos))
>>> > +  (let (pos)
>>> > +    (when (and (setq pos (electric--after-char-pos))
>>> >                 ;; Not in a string or comment.
>>> >                 (not (nth 8 (save-excursion (syntax-ppss pos)))))
>>> > -      (let ((end (point-marker))
>>> > -            (sym (if (functionp rule) (funcall rule) rule)))
>>> > -        (set-marker-insertion-type end (not (eq sym 'after-stay)))
>>> > -        (goto-char pos)
>>> > -        (pcase sym
>>> > -          ;; FIXME: we used `newline' down here which called
>>> > -          ;; self-insert-command and ran post-self-insert-hook recursively.
>>> > -          ;; It happened to make electric-indent-mode work automatically with
>>> > -          ;; electric-layout-mode (at the cost of re-indenting lines
>>> > -          ;; multiple times), but I'm not sure it's what we want.
>>> > -          ;;
>>> > -          ;; FIXME: check eolp before inserting \n?
>>> > -          ('before (goto-char (1- pos)) (skip-chars-backward " \t")
>>> > -                   (unless (bolp) (insert "\n")))
>>> > -          ('after  (insert "\n"))
>>> > -          ('after-stay (save-excursion
>>> > -                         (let ((electric-layout-rules nil))
>>> > -                           (newline 1 t))))
>>> > -          ('around (save-excursion
>>> > -                     (goto-char (1- pos)) (skip-chars-backward " \t")
>>> > -                     (unless (bolp) (insert "\n")))
>>> > -                   (insert "\n")))      ; FIXME: check eolp before inserting \n?
>>> > -        (goto-char end)))))
>>> > +      (goto-char pos)
>>> > +      (dolist (rule electric-layout-rules)
>>> > +        (when (eq last-command-event (car rule))
>>> > +          (let* ((end (point-marker))
>>> > +                 (rule (cdr rule))
>>> > +                 (sym (if (functionp rule) (funcall rule) rule)))
>>> > +            (set-marker-insertion-type end (not (eq sym 'after-stay)))
>>> > +            (pcase sym
>>> > +              ;; FIXME: we used `newline' down here which called
>>> > +              ;; self-insert-command and ran post-self-insert-hook recursively.
>>> > +              ;; It happened to make electric-indent-mode work automatically with
>>> > +              ;; electric-layout-mode (at the cost of re-indenting lines
>>> > +              ;; multiple times), but I'm not sure it's what we want.
>>> > +              ;;
>>> > +              ;; FIXME: check eolp before inserting \n?
>>> > +              ('before (goto-char (1- pos)) (skip-chars-backward " \t")
>>> > +                       (unless (bolp) (insert "\n")))
>>> > +              ('after  (insert "\n"))
>>> > +              ('after-stay (save-excursion
>>> > +                             (let ((electric-layout-rules nil)
>>> > +                                   (electric-pair-open-newline-between-pairs nil))
>>> > +                               (newline 1 t))))
>>> > +              ('around (save-excursion
>>> > +                         (goto-char (1- pos)) (skip-chars-backward " \t")
>>> > +                         (unless (bolp) (insert "\n")))
>>> > +                       (insert "\n")))      ; FIXME: check eolp before inserting \n?
>>> > +            (goto-char end)))))))
>>> >
>>> >  (put 'electric-layout-post-self-insert-function 'priority  40)
>>> >