GNU bug report logs - #60691
29.0.60; Slow tree-sitter font-lock in ruby-ts-mode

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Juri Linkov <juri <at> linkov.net>
To: bug-gnu-emacs <at> gnu.org
Subject: 29.0.60; Slow tree-sitter font-lock in ruby-ts-mode
Date: Mon, 09 Jan 2023 19:16:12 +0200

X-Debbugs-Cc: Dmitry Gutov <dgutov <at> yandex.ru>

After more rules were added recently to ruby-ts--font-lock-settings,
font-lock became slow even on very small files.  Some measurements:

M-: (benchmark-run 1000 (progn (font-lock-mode -1) (font-lock-mode 1) (font-lock-ensure)))

M-x ruby-mode
(1.3564674989999999 0 0.0)

M-x ruby-ts-mode
(8.349582391999999 2 6.489918534000001)

This is not a problem when files are visited infrequently, but
becomes a problem for diff-syntax fontification that wants to
highlight simultaneously many files from git logs.
So a temporary measure would be not to enable ruby-ts-mode
in internal buffers:

(add-hook 'find-file-hook
          (lambda ()
            (when (and (eq major-mode 'ruby-mode)
                       ;; Only when not internal as from diff-syntax
                       (not (string-prefix-p " " (buffer-name))))
              (ruby-ts-mode))))

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