reStructuredText Syntax Highlighting on macOS

[xudongzheng]

Steps to reproduce

The bug can be reproduced with the following command using macOS's builtin Vim.

echo "syntax on" > vimrc
echo "hello CONFIG_SAMPLE_BT_USE_AUTHENTICATION" > test.rst
vim -u vimrc test.rst

This results in 'redrawtime' exceeded, syntax highlighting disabled.

It's hard to say how much of this is a Vim bug and not a macOS issue since I haven't been able to reproduce with similar Vim versions on Debian/etc.

Expected behaviour

Syntax highlighting should work

Version of Vim

9.0.2018

Environment

Operating System: macOS 14.2.1

VIM - Vi IMproved 9.0 (2022 Jun 28, compiled Nov 12 2023 01:16:04) macOS version - arm64 Included patches: 1-2018

Logs and stack traces

No response

[chrisbra]

Hm, I cannot reproduce but then I do not have a mac. Two things: If you compile your own version (e.g. using homebrew), does it show the same issue? What is your option 'redrawtime' value? Can you use :syntime report and check if there are slow queries (See :h syntime) ? Also, can you please post the full :version output?

[xudongzheng]

I have the default redrawtime=2000. syntime unfortunately isn't available in the OS Vim.

I will look into trying a custom compiled Vim but I suspect it's due to the way Apple is compiling it. The issue is present with the default Vim on macOS 12 and macOS 14 but I haven't been able to reproduce the issue on any of my Linux boxes running a variety of Vim versions.

:version
VIM - Vi IMproved 9.0 (2022 Jun 28, compiled Nov 12 2023 01:16:04)
macOS version - arm64
Included patches: 1-2018
Compiled by [email protected]
Normal version without GUI.  Features included (+) or not (-):
+acl               +cmdline_hist      +ex_extra          +jumplist          +mouse_dec         -perl              -sodium            +textobjects       +wildmenu
-arabic            +cmdline_info      +extra_search      -keymap            -mouse_gpm         +persistent_undo   -sound             +textprop          +windows
+autocmd           +comments          -farsi             +lambda            -mouse_jsbterm     +popupwin          +spell             +timers            +writebackup
+autochdir         +conceal           +file_in_path      -langmap           +mouse_netterm     +postscript        +startuptime       +title             -X11
-autoservername    +cryptv            +find_in_path      +libcall           +mouse_sgr         +printer           +statusline        -toolbar           -xattr
-balloon_eval      +cscope            +float             +linebreak         -mouse_sysmouse    -profile           -sun_workshop      +user_commands     -xfontset
-balloon_eval_term +cursorbind        +folding           +lispindent        +mouse_urxvt       -python            +syntax            -vartabs           -xim
-browse            +cursorshape       -footer            +listcmds          +mouse_xterm       -python3           +tag_binary        +vertsplit         -xpm
++builtin_terms    +dialog_con        +fork()            +localmap          +multi_byte        +quickfix          -tag_old_static    +vim9script        -xsmp
+byte_offset       +diff              -gettext           -lua               +multi_lang        +reltime           -tag_any_white     +viminfo           -xterm_clipboard
+channel           +digraphs          -hangul_input      +menu              -mzscheme          -rightleft         -tcl               +virtualedit       -xterm_save
+cindent           -dnd               +iconv             +mksession         +netbeans_intg     -ruby              +termguicolors     +visual
-clientserver      -ebcdic            +insert_expand     +modify_fname      +num64             +scrollbind        +terminal          +visualextra
+clipboard         -emacs_tags        +ipv6              +mouse             +packages          +signs             +terminfo          +vreplace
+cmdline_compl     +eval              +job               -mouseshape        +path_extra        +smartindent       +termresponse      +wildignore
   system vimrc file: "$VIM/vimrc"
     user vimrc file: "$HOME/.vimrc"
 2nd user vimrc file: "~/.vim/vimrc"
      user exrc file: "$HOME/.exrc"
       defaults file: "$VIMRUNTIME/defaults.vim"
  fall-back for $VIM: "/usr/share/vim"
Compilation: gcc -c -I. -Iproto -DHAVE_CONFIG_H   -DMACOS_X_UNIX  -g -O2 -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=1
Linking: gcc   -L/usr/local/lib -o vim        -lm -lncurses  -liconv -framework Cocoa

[xudongzheng]

I did a bit more investigation and the issue disappears if I remove these two lines: https://github.com/vim/vim/blob/d887fb81b6d419d035629f06b918b054d30c5fab/runtime/syntax/rst.vim#L169-L170

\= seems to be responsible part - issue also goes away if I remove that.

My initial guess is that there's some difference between how regular expressions are handled on macOS vs Linux.

I am not familiar enough with these syntax files to know what can be safely removed.

[chrisbra]

I have no idea, why this goes away once you remove the \=. This is used to match the _ optionally at. I don't know the RST markup language, so cannot say what will break.

A few things to try:

• Try if it changes with :set re=1 or :set re=2?
• Can you generate the :syntime report (see :help syntime)

Also pinging @marshallward perhaps he know what this change above would mean to the RST highlighting.

[marshallward]

Single and double underscores should both be recognized. The double underscore indicates an anonymous hyperlink. (.. __: https:/...)

https://docutils.sourceforge.io/docs/ref/rst/restructuredtext.html#hyperlink-targets

This section predates me, and I'm not in a position this week to test anything, so I'm unsure what could be causing the problem. But I don't think that the \= should just be dropped.

[xudongzheng]

@chrisbra thanks for the suggestion.

Syntax highlighting works on macOS without any runtime changes if I set :set re=0 and :set re=2.

Additionally, I'm able to reproduce the issue on all my machines with :set re=1:

echo "hello CONFIG_SAMPLE_BT_USE_AUTHENTICATION" > test.rst
vim --clean -c ":set re=1" -c ":syntax on" test.rst

It seems like re=1 is the default on macOS but :verbose set re? doesn't show anything not sure why it's different.

Result of :syntime report: syntime-report.txt