bug#66153: 30.0.50; treesit: Edge case in indentation with multiple languages

["Augustin Chéneau" <btuin@mailo.com>]

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There is an edge case in treesit with multiple languages
indentation. Here is a simple example:

// language_A
     {
        // language_B
     }
// language_A


Here, brackets are managed by language_A, but everything inside is
managed by language_B.  Meaning that if the pointer is at the beginning
of the third line (with the closing bracket), it will use language_B's
indent rules.  But if the point is located on the bracket, it will use
language_A's rules.



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
SECCOMP SOUND SQLITE3 THREADS TIFF TOOLKIT_SCROLL_BARS TREE_SITTER WEBP
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:
(help-mode pp shadow sort mail-extr emacsbug message mailcap yank-media
puny dired dired-loaddefs rfc822 mml mml-sec password-cache epa derived
epg rfc6068 epg-config gnus-util text-property-search mm-decode
mm-bodies mm-encode mail-parse rfc2231 mailabbrev gmm-utils mailheader
sendmail rfc2047 rfc2045 ietf-drums mm-util mail-prsvr mail-utils
time-date subr-x cl-loaddefs cl-lib rmc iso-transl tooltip cconv eldoc
paren electric uniquify ediff-hook vc-hooks lisp-float-type elisp-mode
mwheel term/x-win x-win term/common-win x-dnd touch-screen tool-bar dnd
fontset image regexp-opt fringe tabulated-list replace newcomment
text-mode lisp-mode prog-mode register page tab-bar menu-bar rfn-eshadow
isearch easymenu timer select scroll-bar mouse jit-lock font-lock syntax
font-core term/tty-colors frame minibuffer nadvice seq simple cl-generic
indonesian philippine cham georgian utf-8-lang misc-lang vietnamese
tibetan thai tai-viet lao korean japanese eucjp-ms cp51932 hebrew greek
romanian slovak czech european ethiopic indian cyrillic chinese
composite emoji-zwj charscript charprop case-table epa-hook
jka-cmpr-hook help abbrev obarray oclosure cl-preloaded button loaddefs
theme-loaddefs faces cus-face macroexp files window text-properties
overlay sha1 md5 base64 format env code-pages mule custom widget keymap
hashtable-print-readable backquote threads dbusbind inotify lcms2
dynamic-setting system-font-setting font-render-setting cairo gtk
x-toolkit xinput2 x multi-tty move-toolbar make-network-process emacs)

Memory information:
((conses 16 41258 25860) (symbols 48 5341 4) (strings 32 13761 2638)
  (string-bytes 1 393134) (vectors 16 10548)
  (vector-slots 8 159589 13619) (floats 8 24 71) (intervals 56 339 40)
  (buffers 992 11))

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From a72df328a1195328a364be20612be189eb2dfd59 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Augustin=20Ch=C3=A9neau?= <btuin@mailo.com>
Date: Wed, 20 Sep 2023 12:23:22 +0200
Subject: [PATCH 2/3] Fix tree-sitter indentation conflict with multiple
 languages

---
 lisp/treesit.el | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lisp/treesit.el b/lisp/treesit.el
index f0d6f32b421..0bb3aa6d653 100644
--- a/lisp/treesit.el
+++ b/lisp/treesit.el
@@ -1684,8 +1684,8 @@ treesit--indent-1
                                 bol (car local-parsers)))
                 ((eq 1 (length (treesit-parser-list nil nil t)))
                  (treesit-node-at bol))
-                ((treesit-language-at (point))
-                 (treesit-node-at bol (treesit-language-at (point))))
+                ((treesit-language-at bol)
+                 (treesit-node-at bol (treesit-language-at bol)))
                 (t (treesit-node-at bol))))
          (root (treesit-parser-root-node
                 (treesit-node-parser smallest-node)))
-- 
2.42.0