bug#64830: 30.0.50 C++ treesitter mode no coloration

[Yuan Fu <casouri@gmail.com>]

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> On Aug 19, 2024, at 8:46 PM, Yuan Fu <casouri@gmail.com> wrote:
> 
> 
> 
>> On Aug 16, 2024, at 11:27 AM, Eli Zaretskii <eliz@gnu.org> wrote:
>> 
>>> Date: Fri, 16 Aug 2024 18:06:31 +0000
>>> Cc: 64830@debbugs.gnu.org, casouri@gmail.com, acm@muc.de
>>> From: Alan Mackenzie <acm@muc.de>
>>> 
>>>> Maybe your Emacs 30 build is old?
>>> 
>>> No.  I updated it on Wednesday, the most recent commit I have being:
>>> 
>>> commit 9bedb957bebdca99b1bb96f58ea790e20ed48dee (HEAD -> emacs-30,
>>> origin/emacs-30)
>>> Author: Eli Zaretskii <eliz@gnu.org>
>>> Date:   Wed Aug 14 11:35:48 2024 +0300
>>> 
>>>   Improve documentation of time-parsing functions
>>> 
>>> ..  I will update it right now and retry ....
>>> 
>>> ..... DONE.  It makes no difference.  I don't understand either why I see
>>> this bug and you don't.
>> 
>> Maybe try updating the C++ grammar library?
>> 
>> Yuan, any ideas?
> 
> Nothing obviously wrong from a glance. I’m very busy recently but I’ll have some time this week to look into this. Sorry for the delay :-)
> 
> Yuan

Upon closer inspection, I think this is caused by a recent change in c-ts-mode font-lock rules, in 014aab9847a0d3d898cb8cbc7224143f2d741abb.

Alan, could you do this: don’t upgrade your c++ grammar and try this patch, if I was right it should fix your problem. Thanks!

Yuan


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From a171709cadd915f48d6c8ed3f9e1e19f6a4fde19 Mon Sep 17 00:00:00 2001
From: Yuan Fu <casouri@gmail.com>
Date: Sat, 24 Aug 2024 11:32:43 -0700
Subject: [PATCH] Fix c-ts-mode font-lock for older c++ grammar (bug#64830)

* lisp/progmodes/c-ts-mode.el:
(c-ts-mode--virtual-named-p): New function.
(c-ts-mode--font-lock-settings): Use either keyword or named node
depending on grammar version.
---
 lisp/progmodes/c-ts-mode.el | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/lisp/progmodes/c-ts-mode.el b/lisp/progmodes/c-ts-mode.el
index 6c406a8acd9..66e4999677b 100644
--- a/lisp/progmodes/c-ts-mode.el
+++ b/lisp/progmodes/c-ts-mode.el
@@ -537,6 +537,16 @@ c-ts-mode--top-level-label-matcher
        (equal "function_definition"
               (treesit-node-type (treesit-node-parent parent)))))
 
+;;; Grammar checks
+
+;; Ref: https://github.com/tree-sitter/tree-sitter-cpp/commit/c51ffe9d7b67aa9500db01c26d8c075cfe032d0f
+(defun c-ts-mode--virtual-named-p ()
+  "Return t if virtual is a named node instead of a keyword."
+  (ignore-errors
+    (progn
+      (treesit-query-compile 'c++ "(virtual) @cap")
+      t)))
+
 ;;; Font-lock
 
 (defvar c-ts-mode--feature-list
@@ -635,9 +645,11 @@ c-ts-mode--font-lock-settings
    :feature 'keyword
    `([,@(c-ts-mode--keywords mode)] @font-lock-keyword-face
      ,@(when (eq mode 'cpp)
-         '((auto) @font-lock-keyword-face
+         `((auto) @font-lock-keyword-face
            (this) @font-lock-keyword-face
-           (virtual) @font-lock-keyword-face)))
+           ,@(if (c-ts-mode--virtual-named-p)
+                 '((virtual) @font-lock-keyword-face)
+               '("virtual" @font-lock-keyword-face)))))
 
    :language mode
    :feature 'operator
-- 
2.39.5 (Apple Git-151)