xxx took too long, syntax highlighting disabled

[dimaqq]

I've found a pathological case where vim becomes almost unusable.

The trick is to open a file that's not really a Python file, but try to syntax highlight it and annotated with pyright errors as if it were Python code.

Note that syntax highlighting alone works well enough.

Information

VIM version

VIM - Vi IMproved 9.1 (2024 Jan 02, compiled Aug 28 2024 20:08:35)
macOS version - arm64
Included patches: 1-700
Compiled by Homebrew
Huge version without GUI.  Features included (+) or not (-):
+acl               +cindent           +cursorshape       +file_in_path      +job               +menu              +mouse_urxvt       +popupwin          +signs             -tag_any_white     +user_commands     +windows
+arabic            -clientserver      +dialog_con        +find_in_path      +jumplist          +mksession         +mouse_xterm       +postscript        +smartindent       -tcl               +vartabs           +writebackup
+autocmd           +clipboard         +diff              +float             +keymap            +modify_fname      +multi_byte        +printer           +sodium            +termguicolors     +vertsplit         -X11
+autochdir         +cmdline_compl     +digraphs          +folding           +lambda            +mouse             +multi_lang        +profile           +sound             +terminal          +vim9script        -xattr
-autoservername    +cmdline_hist      -dnd               -footer            +langmap           -mouseshape        -mzscheme          -python            +spell             +terminfo          +viminfo           -xfontset
-balloon_eval      +cmdline_info      -ebcdic            +fork()            +libcall           +mouse_dec         +netbeans_intg     +python3           +startuptime       +termresponse      +virtualedit       -xim
+balloon_eval_term +comments          +emacs_tags        +gettext           +linebreak         -mouse_gpm         +num64             +quickfix          +statusline        +textobjects       +visual            -xpm
-browse            +conceal           +eval              -hangul_input      +lispindent        -mouse_jsbterm     +packages          +reltime           -sun_workshop      +textprop          +visualextra       -xsmp
++builtin_terms    +cryptv            +ex_extra          +iconv             +listcmds          +mouse_netterm     +path_extra        +rightleft         +syntax            +timers            +vreplace          -xterm_clipboard
+byte_offset       +cscope            +extra_search      +insert_expand     +localmap          +mouse_sgr         +perl              +ruby              +tag_binary        +title             +wildignore        -xterm_save
+channel           +cursorbind        -farsi             +ipv6              +lua               -mouse_sysmouse    +persistent_undo   +scrollbind        -tag_old_static    -toolbar           +wildmenu
   system vimrc file: "$VIM/vimrc"
     user vimrc file: "$HOME/.vimrc"
 2nd user vimrc file: "~/.vim/vimrc"
 3rd user vimrc file: "~/.config/vim/vimrc"
      user exrc file: "$HOME/.exrc"
       defaults file: "$VIMRUNTIME/defaults.vim"
  fall-back for $VIM: "/opt/homebrew/share/vim"
Compilation: clang -c -I. -Iproto -DHAVE_CONFIG_H -DMACOS_X -DMACOS_X_DARWIN -g -O2 -D_REENTRANT -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=1
Linking: clang -o vim -lm -lncurses -lsodium -liconv -lintl -framework AppKit -L/opt/homebrew/opt/lua/lib -llua5.4 -mmacosx-version-min=14.2 -fstack-protector-strong -L/opt/homebrew/opt/perl/lib/perl5/5.38/darwin-thread-multi-2level/CORE -lperl -L/opt/h
omebrew/opt/python@3.12/Frameworks/Python.framework/Versions/3.12/lib/python3.12/config-3.12-darwin -lpython3.12 -framework CoreFoundation -lruby.3.3 -L/opt/homebrew/Cellar/ruby/3.3.4/lib

Reproducing the bug

Run a virualenv with pyright installed (maybe other tools like ruff of mypy would do as well).
Grab https://gist.github.com/dimaqq/925afea05590de55abd49ab631612738
Open it in vim.
Wait.
Wait some more...
Watch the screen fill in slowly with annotations.