bug#66152: 30.0.50; Missing indent rules in c-ts-mode

bug#66152: 30.0.50; Missing indent rules in c-ts-mode

[Augustin Chéneau]

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There are missing indent rules in c-ts-mode.
Currently there is no rule if an identifier in a declaration is on a new
line. In these two cases, "variable_name" is not indented:

static myttype *
variable_name;

static myttype
variable_name;

The new behavior is the same as c-mode.


In GNU Emacs 30.0.50 (build 3, x86_64-pc-linux-gnu, GTK+ Version
  3.24.38, cairo version 1.17.8) of 2023-09-19 built on inspiron-5567
Repository revision: 991bf3f0f5dff66794785ebfcc867611fe75e0da
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12302001
System Description: Arch Linux

Configured using:
  'configure PKG_CONFIG_PATH=/home/arch-aug/.opam/default/lib/pkgconfig:'

Configured features:
ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GPM GSETTINGS HARFBUZZ JPEG
JSON LCMS2 LIBSYSTEMD LIBXML2 MODULES NOTIFY INOTIFY PDUMPER PNG RSVG
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X11 XDBE XIM XINPUT2 XPM GTK3 ZLIB

Important settings:
   value of $LANG: fr_FR.UTF-8
   locale-coding-system: utf-8-unix

Major mode: Lisp Interaction

Minor modes in effect:
   tooltip-mode: t
   global-eldoc-mode: t
   eldoc-mode: t
   show-paren-mode: t
   electric-indent-mode: t
   mouse-wheel-mode: t
   tool-bar-mode: t
   menu-bar-mode: t
   file-name-shadow-mode: t
   global-font-lock-mode: t
   font-lock-mode: t
   blink-cursor-mode: t
   minibuffer-regexp-mode: t
   line-number-mode: t
   indent-tabs-mode: t
   transient-mark-mode: t
   auto-composition-mode: t
   auto-encryption-mode: t
   auto-compression-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message mailcap yank-media puny dired
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dynamic-setting system-font-setting font-render-setting cairo gtk
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Memory information:
((conses 16 37844 9140) (symbols 48 5209 0) (strings 32 13243 1761)
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[-- Attachment #2: 0001-Add-missing-indent-rules-in-c-ts-mode.patch --]
[-- Type: text/x-patch, Size: 998 bytes --]

From 2d5248d9612feb6e55bf9e22e5d8bc1b8f565ba8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Augustin=20Ch=C3=A9neau?= <btuin@mailo.com>
Date: Wed, 20 Sep 2023 12:23:06 +0200
Subject: [PATCH 1/3] Add missing indent rules in c-ts-mode

---
 lisp/progmodes/c-ts-mode.el | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/lisp/progmodes/c-ts-mode.el b/lisp/progmodes/c-ts-mode.el
index 70717a90caa..314f37f7ec5 100644
--- a/lisp/progmodes/c-ts-mode.el
+++ b/lisp/progmodes/c-ts-mode.el
@@ -407,6 +407,8 @@ c-ts-mode--indent-styles
            ((parent-is "preproc") c-ts-mode--anchor-prev-sibling 0)
 
            ((parent-is "function_definition") parent-bol 0)
+           ((parent-is "pointer_declarator") parent-bol 0)
+           ((parent-is "declaration") parent-bol 0)
            ((parent-is "conditional_expression") first-sibling 0)
            ((parent-is "assignment_expression") parent-bol c-ts-mode-indent-offset)
            ((parent-is "concatenated_string") first-sibling 0)
-- 
2.42.0

bug#66152: 30.0.50; Missing indent rules in c-ts-mode

[Augustin Chéneau]

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I found some more issues.

First, there is no rule for an element in an else clause:


if (true)
   do_something();
else
do_something_else();


"do_something_else" is not indented.

There is also something weird with the bsd indent style.  It indents 
do_something and do_something_else to parent-bol with 0 offset, so the 
result is:

if (true)
do_something();
else
do_something_else();


It is very different from the bsd style from c-mode, which produces this:

if (true)
	do_something();
else
	do_something_else();

By looking at random files from OpenBSD, they do indent their 
expressions inside if and else:

<https://cvsweb.openbsd.org/cgi-bin/cvsweb/~checkout~/src/sys/net/bsd-comp.c?rev=1.17&content-type=text/plain>
(lines 277, 484, and 527)



Also there is a second patch which tries to handle specific types of 
comments.  I don't know how popular it is, but some people use these 
kind of comments:

/*---------.
| %param.  |
`---------*/

Here we want the vertical bar ("|") to be indented at the same column as 
the first "/".

Currently the result is this:

/*---------.
   | %param.  |
   `---------*/

This patch is a just proof of concept.  If this new behavior is indeed 
wanted, I would clean it up and adapt other modes.

[-- Attachment #2: 0001-c-ts-mode-Add-indentation-rule-for-else_clause.patch --]
[-- Type: text/x-patch, Size: 1101 bytes --]

From d050619743b2604dfa3b1342fa12ee99a4aa550a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Augustin=20Ch=C3=A9neau?= <btuin@mailo.com>
Date: Tue, 26 Sep 2023 14:03:18 +0200
Subject: [PATCH 1/2] c-ts-mode: Add indentation rule for else_clause

---
 lisp/progmodes/c-ts-mode.el | 1 +
 1 file changed, 1 insertion(+)

diff --git a/lisp/progmodes/c-ts-mode.el b/lisp/progmodes/c-ts-mode.el
index 314f37f7ec5..cb236447368 100644
--- a/lisp/progmodes/c-ts-mode.el
+++ b/lisp/progmodes/c-ts-mode.el
@@ -455,6 +455,7 @@ c-ts-mode--indent-styles
            ;; These rules are for cases where the body is bracketless.
            ;; Tested by the "Bracketless Simple Statement" test.
            ((parent-is "if_statement") standalone-parent c-ts-mode-indent-offset)
+           ((parent-is "else_clause") standalone-parent c-ts-mode-indent-offset)
            ((parent-is "for_statement") standalone-parent c-ts-mode-indent-offset)
            ((parent-is "while_statement") standalone-parent c-ts-mode-indent-offset)
            ((parent-is "do_statement") standalone-parent c-ts-mode-indent-offset)
-- 
2.42.0


[-- Attachment #3: 0002-c-ts-mode-handle-specific-comment-formatting.patch --]
[-- Type: text/x-patch, Size: 1928 bytes --]

From 0074db4224b4269eec464ac00eb751d919aec408 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Augustin=20Ch=C3=A9neau?= <btuin@mailo.com>
Date: Tue, 26 Sep 2023 14:10:40 +0200
Subject: [PATCH 2/2] c-ts-mode: handle specific comment formatting

---
 lisp/progmodes/c-ts-common.el | 11 +++++++++++
 lisp/progmodes/c-ts-mode.el   |  4 +++-
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/lisp/progmodes/c-ts-common.el b/lisp/progmodes/c-ts-common.el
index 3b0814970ad..1ea41260ab8 100644
--- a/lisp/progmodes/c-ts-common.el
+++ b/lisp/progmodes/c-ts-common.el
@@ -56,6 +56,17 @@
 
 ;;; Comment indentation and filling
 
+
+(defun c-ts-common-looking-at (char &rest chars)
+  (lambda (_n _p bol &rest _)
+    (let ((res nil))
+      (setq res (eq (char-after bol) char))
+      (while (and chars (not res))
+        (setq char (car chars)
+              chars (cdr chars)
+              res (eq (char-after bol) char)))
+      res)))
+
 (defun c-ts-common-looking-at-star (_n _p bol &rest _)
   "A tree-sitter simple indent matcher.
 Matches if there is a \"*\" after BOL."
diff --git a/lisp/progmodes/c-ts-mode.el b/lisp/progmodes/c-ts-mode.el
index cb236447368..76cbad50d06 100644
--- a/lisp/progmodes/c-ts-mode.el
+++ b/lisp/progmodes/c-ts-mode.el
@@ -371,8 +371,10 @@ c-ts-mode--indent-styles
            ((node-is "preproc_arg") no-indent)
            ;; `c-ts-common-looking-at-star' has to come before
            ;; `c-ts-common-comment-2nd-line-matcher'.
-           ((and (parent-is "comment") c-ts-common-looking-at-star)
+           ((and (parent-is "comment") c-ts-common-looking-at ?*)
             c-ts-common-comment-start-after-first-star -1)
+           ((and (parent-is "comment") (c-ts-common-looking-at ?| ?\\ ?`))
+            c-ts-common-comment-start-after-first-star -2)
            (c-ts-common-comment-2nd-line-matcher
             c-ts-common-comment-2nd-line-anchor
             1)
-- 
2.42.0

bug#66152: 30.0.50; Missing indent rules in c-ts-mode

[Eli Zaretskii]

> Date: Tue, 26 Sep 2023 14:29:07 +0200
> From: Augustin Chéneau (BTuin) <btuin@mailo.com>
> 
> I found some more issues.
> 
> First, there is no rule for an element in an else clause:
> 
> 
> if (true)
>    do_something();
> else
> do_something_else();
> 
> 
> "do_something_else" is not indented.
> 
> There is also something weird with the bsd indent style.  It indents 
> do_something and do_something_else to parent-bol with 0 offset, so the 
> result is:
> 
> if (true)
> do_something();
> else
> do_something_else();
> 
> 
> It is very different from the bsd style from c-mode, which produces this:
> 
> if (true)
> 	do_something();
> else
> 	do_something_else();
> 
> By looking at random files from OpenBSD, they do indent their 
> expressions inside if and else:
> 
> <https://cvsweb.openbsd.org/cgi-bin/cvsweb/~checkout~/src/sys/net/bsd-comp.c?rev=1.17&content-type=text/plain>
> (lines 277, 484, and 527)
> 
> 
> 
> Also there is a second patch which tries to handle specific types of 
> comments.  I don't know how popular it is, but some people use these 
> kind of comments:
> 
> /*---------.
> | %param.  |
> `---------*/
> 
> Here we want the vertical bar ("|") to be indented at the same column as 
> the first "/".
> 
> Currently the result is this:
> 
> /*---------.
>    | %param.  |
>    `---------*/
> 
> This patch is a just proof of concept.  If this new behavior is indeed 
> wanted, I would clean it up and adapt other modes.

Yuan, any comments?  If the first patch looks good to you, I'd like to
install it on the release branch.

bug#66152: 30.0.50; Missing indent rules in c-ts-mode

[Eli Zaretskii]

Ping!  Yuan, I would really like to use the first patch in Emacs 29.2,
if it looks OK to you.

> Cc: 66152@debbugs.gnu.org
> Date: Fri, 29 Sep 2023 10:17:29 +0300
> From: Eli Zaretskii <eliz@gnu.org>
> 
> > Date: Tue, 26 Sep 2023 14:29:07 +0200
> > From: Augustin Chéneau (BTuin) <btuin@mailo.com>
> > 
> > I found some more issues.
> > 
> > First, there is no rule for an element in an else clause:
> > 
> > 
> > if (true)
> >    do_something();
> > else
> > do_something_else();
> > 
> > 
> > "do_something_else" is not indented.
> > 
> > There is also something weird with the bsd indent style.  It indents 
> > do_something and do_something_else to parent-bol with 0 offset, so the 
> > result is:
> > 
> > if (true)
> > do_something();
> > else
> > do_something_else();
> > 
> > 
> > It is very different from the bsd style from c-mode, which produces this:
> > 
> > if (true)
> > 	do_something();
> > else
> > 	do_something_else();
> > 
> > By looking at random files from OpenBSD, they do indent their 
> > expressions inside if and else:
> > 
> > <https://cvsweb.openbsd.org/cgi-bin/cvsweb/~checkout~/src/sys/net/bsd-comp.c?rev=1.17&content-type=text/plain>
> > (lines 277, 484, and 527)
> > 
> > 
> > 
> > Also there is a second patch which tries to handle specific types of 
> > comments.  I don't know how popular it is, but some people use these 
> > kind of comments:
> > 
> > /*---------.
> > | %param.  |
> > `---------*/
> > 
> > Here we want the vertical bar ("|") to be indented at the same column as 
> > the first "/".
> > 
> > Currently the result is this:
> > 
> > /*---------.
> >    | %param.  |
> >    `---------*/
> > 
> > This patch is a just proof of concept.  If this new behavior is indeed 
> > wanted, I would clean it up and adapt other modes.
> 
> Yuan, any comments?  If the first patch looks good to you, I'd like to
> install it on the release branch.
> 
> 
> 
> 

bug#66152: 30.0.50; Missing indent rules in c-ts-mode

[Yuan Fu]

On 10/5/23 12:16 AM, Eli Zaretskii wrote:
> Ping!  Yuan, I would really like to use the first patch in Emacs 29.2,
> if it looks OK to you.
>
>> Cc: 66152@debbugs.gnu.org
>> Date: Fri, 29 Sep 2023 10:17:29 +0300
>> From: Eli Zaretskii <eliz@gnu.org>
>>
>>> Date: Tue, 26 Sep 2023 14:29:07 +0200
>>> From: Augustin Chéneau (BTuin) <btuin@mailo.com>
>>>
>>> I found some more issues.
>>>
>>> First, there is no rule for an element in an else clause:
>>>
>>>
>>> if (true)
>>>     do_something();
>>> else
>>> do_something_else();
>>>
>>>
>>> "do_something_else" is not indented.
>>>
>>> There is also something weird with the bsd indent style.  It indents
>>> do_something and do_something_else to parent-bol with 0 offset, so the
>>> result is:
>>>
>>> if (true)
>>> do_something();
>>> else
>>> do_something_else();
>>>
>>>
>>> It is very different from the bsd style from c-mode, which produces this:
>>>
>>> if (true)
>>> 	do_something();
>>> else
>>> 	do_something_else();
>>>
>>> By looking at random files from OpenBSD, they do indent their
>>> expressions inside if and else:
>>>
>>> <https://cvsweb.openbsd.org/cgi-bin/cvsweb/~checkout~/src/sys/net/bsd-comp.c?rev=1.17&content-type=text/plain>
>>> (lines 277, 484, and 527)
>>>
>>>
>>>
>>> Also there is a second patch which tries to handle specific types of
>>> comments.  I don't know how popular it is, but some people use these
>>> kind of comments:
>>>
>>> /*---------.
>>> | %param.  |
>>> `---------*/
>>>
>>> Here we want the vertical bar ("|") to be indented at the same column as
>>> the first "/".
>>>
>>> Currently the result is this:
>>>
>>> /*---------.
>>>     | %param.  |
>>>     `---------*/
>>>
>>> This patch is a just proof of concept.  If this new behavior is indeed
>>> wanted, I would clean it up and adapt other modes.
>> Yuan, any comments?  If the first patch looks good to you, I'd like to
>> install it on the release branch.
LGTM, I applied the first patch to emacs-29.

Yuan

bug#66152: 30.0.50; Missing indent rules in c-ts-mode

[Stefan Kangas]

Yuan Fu <casouri@gmail.com> writes:

> LGTM, I applied the first patch to emacs-29.

What about patch 2 and 3?  Should they be installed on master?

bug#66152: 30.0.50; Missing indent rules in c-ts-mode

[Eli Zaretskii]

> From: Stefan Kangas <stefankangas@gmail.com>
> Date: Wed, 10 Jan 2024 13:31:37 -0800
> Cc: Eli Zaretskii <eliz@gnu.org>, btuin@mailo.com, 66152@debbugs.gnu.org
> 
> Yuan Fu <casouri@gmail.com> writes:
> 
> > LGTM, I applied the first patch to emacs-29.
> 
> What about patch 2 and 3?  Should they be installed on master?

Not sure.  It sounded like they were experimental, and no consensus
was reached.

bug#66152: 30.0.50; Missing indent rules in c-ts-mode

[Yuan Fu]

> On Jan 10, 2024, at 10:24 PM, Eli Zaretskii <eliz@gnu.org> wrote:
> 
>> From: Stefan Kangas <stefankangas@gmail.com>
>> Date: Wed, 10 Jan 2024 13:31:37 -0800
>> Cc: Eli Zaretskii <eliz@gnu.org>, btuin@mailo.com, 66152@debbugs.gnu.org
>> 
>> Yuan Fu <casouri@gmail.com> writes:
>> 
>>> LGTM, I applied the first patch to emacs-29.
>> 
>> What about patch 2 and 3?  Should they be installed on master?
> 
> Not sure.  It sounded like they were experimental, and no consensus
> was reached.

I had a look again, the first patch is applied, the second patch is fixed in another report, the third patch is still in discussion. Augustin said he’ll clean it up and extend it to apply to other modes if it’s desirable. I think it’s good to have, we just need to make sure it doesn’t bring any regression. Also I don’t know how widely used is this kind of comments and how important it is.

Yuan

bug#66152: 30.0.50; Missing indent rules in c-ts-mode

[Stefan Kangas]

Yuan Fu <casouri@gmail.com> writes:

> I had a look again, the first patch is applied, the second patch is fixed in
> another report,

Thanks.

> the third patch is still in discussion. Augustin said he’ll
> clean it up and extend it to apply to other modes if it’s desirable. I think
> it’s good to have, we just need to make sure it doesn’t bring any
> regression. Also I don’t know how widely used is this kind of comments and how
> important it is.

I guess it's for indenting this kind of comment?

    /*---------.
    | %param.  |
    `---------*/

I have no idea either.  Are there any significant projects that use it?

bug#66152: 30.0.50; Missing indent rules in c-ts-mode

[Eli Zaretskii]

> From: Stefan Kangas <stefankangas@gmail.com>
> Date: Sat, 13 Jan 2024 23:33:05 -0600
> Cc: Eli Zaretskii <eliz@gnu.org>, btuin@mailo.com, 66152@debbugs.gnu.org
> 
> Yuan Fu <casouri@gmail.com> writes:
> 
> > the third patch is still in discussion. Augustin said he’ll
> > clean it up and extend it to apply to other modes if it’s desirable. I think
> > it’s good to have, we just need to make sure it doesn’t bring any
> > regression. Also I don’t know how widely used is this kind of comments and how
> > important it is.
> 
> I guess it's for indenting this kind of comment?
> 
>     /*---------.
>     | %param.  |
>     `---------*/
> 
> I have no idea either.  Are there any significant projects that use it?

IMO, it would be nice to be able to support box comments.  I've seen
it in the wild enough to know that some people prefer this style.

bug#66152: 30.0.50; Missing indent rules in c-ts-mode

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

Le 14/01/2024 à 06:33, Stefan Kangas a écrit :
> Yuan Fu <casouri@gmail.com> writes:
> 
>> I had a look again, the first patch is applied, the second patch is fixed in
>> another report,
> 
> Thanks.
> 
>> the third patch is still in discussion. Augustin said he’ll
>> clean it up and extend it to apply to other modes if it’s desirable. I think
>> it’s good to have, we just need to make sure it doesn’t bring any
>> regression. Also I don’t know how widely used is this kind of comments and how
>> important it is.
> 
> I guess it's for indenting this kind of comment?
> 
>      /*---------.
>      | %param.  |
>      `---------*/
> 
> I have no idea either.  Are there any significant projects that use it?


Yes, it is for indenting these kind of comments.

It depends on your definition of "significant", but GNU Bison sometimes 
uses it (example: 
<https://git.savannah.gnu.org/cgit/bison.git/tree/src/getargs.c#n171>).
However I don't know if it is more widely used, if some convention exist 
or if pretty much everyone has his own style.

It could be more annoying than helpful if it messes with your personal 
style, though.

In any case I won't be able to contribute for a while, as I recently 
moved to a new company. They never did copyright assignment and they are 
quite fussy (understandably) on copyright issues.

bug#66152: 30.0.50; Missing indent rules in c-ts-mode

[Yuan Fu]

On 9/26/23 5:29 AM, Augustin Chéneau (BTuin) wrote:
> I found some more issues.
>
> First, there is no rule for an element in an else clause:
>
>
> if (true)
>   do_something();
> else
> do_something_else();
>
>
> "do_something_else" is not indented.

Right. tree-sitter-c recently changed their grammar and added 
else_clause. The fix for this is pushed to emacs-29 a few days ago.

>
> There is also something weird with the bsd indent style.  It indents 
> do_something and do_something_else to parent-bol with 0 offset, so the 
> result is:
>
> if (true)
> do_something();
> else
> do_something_else();
>
>
> It is very different from the bsd style from c-mode, which produces this:
>
> if (true)
>     do_something();
> else
>     do_something_else();
>
> By looking at random files from OpenBSD, they do indent their 
> expressions inside if and else:
>
> <https://cvsweb.openbsd.org/cgi-bin/cvsweb/~checkout~/src/sys/net/bsd-comp.c?rev=1.17&content-type=text/plain> 
>
> (lines 277, 484, and 527)
>
Thanks for reporting this, probably not a lot of people use c-ts-mode 
with bsd style, and things like this goes under the radar. I pushed a 
fix for it.

>
> Also there is a second patch which tries to handle specific types of 
> comments.  I don't know how popular it is, but some people use these 
> kind of comments:
>
> /*---------.
> | %param.  |
> `---------*/
>
> Here we want the vertical bar ("|") to be indented at the same column 
> as the first "/".
>
> Currently the result is this:
>
> /*---------.
>   | %param.  |
>   `---------*/
>
> This patch is a just proof of concept.  If this new behavior is indeed 
> wanted, I would clean it up and adapt other modes.

The gallery of artisan C comments is just endless :-) If we can support 
this style, it's definitely good, the only thing to watch out for is 
that the rules could unintentionally match some other comments that 
aren't really this style. Like, does people do this:

/*
  |
  |
  |
  */

in the wild? I don't know, maybe we need a embedded gpt-4 for formatting 
comments.

Yuan