bug#65182: 29.1.50; c-ts-mode wants to outdent brace

[Yuan Fu]

> On Aug 9, 2023, at 9:34 AM, Eli Zaretskii <eliz@gnu.org> wrote:
> 
>> From: Robert Pluim <rpluim@gmail.com>
>> Cc: Yuan Fu <casouri@gmail.com>,  65182@debbugs.gnu.org
>> Date: Wed, 09 Aug 2023 18:30:44 +0200
>> 
>>>>>>> On Wed, 09 Aug 2023 19:26:10 +0300, Eli Zaretskii <eliz@gnu.org> said:
>> 
>>>> From: Robert Pluim <rpluim@gmail.com>
>>>> Date: Wed, 09 Aug 2023 17:24:44 +0200
>>>> 
>>>> 
>>>>> From an emacs-29 checkout:
>>>> 
>>>> src/emacs -Q src/process.c
>>>> M-g g 6025 RET
>>>> TAB ; nothing happens
>>>> M-x c-ts-mode
>>>> TAB ; the '{' moves left two spaces
>>>> 
>>>> The code around there looks like this:
>>>> 
>>>> #ifdef HAVE_GNUTLS
>>>> /* If we have an incompletely set up TLS connection,
>>>> then defer the sentinel signaling until
>>>> later. */
>>>> if (NILP (p->gnutls_boot_parameters)
>>>> && !p->gnutls_p)
>>>> #endif
>>>> { <= line 6025
>>>> pset_status (p, Qrun);
>>>> /* Execute the sentinel here.  If we had relied on
>>>> status_notify to do it later, it will read input
>>>> from the process before calling the sentinel.  */
>>>> exec_sentinel (proc, build_string ("open\n"));
>>>> }
>>>> 
>>>> Iʼd tell you what my libtree-sitter-c version was if I knew how to get
>>>> that information. I installed it on July 28th
>>>> 
>>>> (I donʼt think this is a duplicate of bug#65006, the patch there does
>>>> not affect this behaviour)
>> 
>>    Eli> It's most probably because of the preprocessor mess around the line.
>> 
>> Maybe, but c-mode works fine.
> 
> Sure.  The problem with c-ts-mode is because the tree-sitter C parser
> doesn't really grok cpp directives, since they are not part of the C
> language grammar.  We have some workarounds in some cases, but I'll
> let Yuan chime in about this particular one.

It’s the same problem: tree-sitter grammar can’t meaningfully parse directives. 
Whatever in the directives are severed from the main parse tree. And to give 
you guys an explanation, the bracket is outdented because the if part isn’t 
taken into consideration, and the bracket is outdented against bracket one 
level higher.

              else
                {            <--------- outdented against this
#ifdef HAVE_GNUTLS   
                  /* If we have an incompletely set up TLS connection,
                     then defer the sentinel signaling until
                     later. */
                  if (NILP (p->gnutls_boot_parameters) <---- the if is ignored
                      && !p->gnutls_p)
#endif
                    {       <------------- outdented
                      pset_status (p, Qrun);
                      /* Execute the sentinel here.  If we had relied on
                         status_notify to do it later, it will read input
                         from the process before calling the sentinel.  */
                      exec_sentinel (proc, build_string ("open\n"));
                    }

Yuan