vim hangs when I open a typescript file

Question

I have a vim 8.2 on a Gentoo Linux running on a more or less 8 years old PC.

I almost never have a performance issue with vim, unless you open a one-line huge xml oder json file, but those are vary rare cases.

My team has started using typescript and so many of our javascript files have been transformed to ts. I use vim-plug for plugging management and I added the HerringtonDarkholme/yats.vim plugin.

However if I open a typescript file, even smaller ones, vim starts normally but after a few seconds it gets very unresponsive, if I scroll down the syntax highlight is also gone and eventually vim hangs. Looking at the process with htop I can see that the process is constantly running at 100% CPU. The only thing I can do is a kill -9.

Vim 8.2 (or at least the Gentoo version) has support for typescript in the default installation, looking at the files in /usr/share/vim/vim82 the provided files seems to be the same as the ones from the yats plugin.

So to be sure that I don't have other plugins interfering, I made a backup of my vim config and remove it from my HOME directory.

The yats github page says to explitly set set re=1, so I created a new ~/.vimrc file and added this line to it. When I open the typescript file, I get the same result, so my other plugins didn't affect it at all.

So the set re=1 made me curious and if I set it instead to 2 or 0 (the default), then opening the same typescript file does not lead vim to hang.

So, did I understand the warning on the github page correctly and I should add set re=1? If so, why is it worse for me?

How can you check what exactly in a plugin is making vim go crazy?

In case this is somehow important:

$ vim --version
VIM - Vi IMproved 8.2 (2019 Dec 12, compiled Apr  4 2020 16:30:54)
Included patches: 1-360
Modified by Gentoo-8.2.0360
Compiled by shaoran@gallifrey
Huge version without GUI.  Features included (+) or not (-):
+acl               -farsi             -mouse_sysmouse    -tag_old_static
+arabic            +file_in_path      +mouse_urxvt       -tag_any_white
+autocmd           +find_in_path      +mouse_xterm       -tcl
+autochdir         +float             +multi_byte        +termguicolors
-autoservername    +folding           +multi_lang        -terminal
-balloon_eval      -footer            -mzscheme          +terminfo
+balloon_eval_term +fork()            +netbeans_intg     +termresponse
-browse            +gettext           +num64             +textobjects
++builtin_terms    -hangul_input      +packages          +textprop
+byte_offset       +iconv             +path_extra        +timers
+channel           +insert_expand     -perl              +title
+cindent           +job               +persistent_undo   -toolbar
+clientserver      +jumplist          +popupwin          +user_commands
+clipboard         +keymap            +postscript        +vartabs
+cmdline_compl     +lambda            +printer           +vertsplit
+cmdline_hist      +langmap           +profile           +virtualedit
+cmdline_info      +libcall           -python            +visual
+comments          +linebreak         +python3           +visualextra
+conceal           +lispindent        +quickfix          +viminfo
+cryptv            +listcmds          +reltime           +vreplace
-cscope            +localmap          +rightleft         +wildignore
+cursorbind        -lua               +ruby              +wildmenu
+cursorshape       +menu              +scrollbind        +windows
+dialog_con        +mksession         +signs             +writebackup
+diff              +modify_fname      +smartindent       +X11
+digraphs          +mouse             -sound             +xfontset
-dnd               -mouseshape        +spell             -xim
-ebcdic            +mouse_dec         +startuptime       -xpm
+emacs_tags        +mouse_gpm         +statusline        +xsmp_interact
+eval              -mouse_jsbterm     -sun_workshop      +xterm_clipboard
+ex_extra          +mouse_netterm     +syntax            -xterm_save
+extra_search      +mouse_sgr         +tag_binary        
   system vimrc file: "/etc/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: x86_64-pc-linux-gnu-gcc -c -I. -Iproto -DHAVE_CONFIG_H     -O2 -pipe -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=1       
Linking: x86_64-pc-linux-gnu-gcc   -L. -Wl,-O1 -fstack-protector -rdynamic -Wl,-export-dynamic -Wl,--no-undefined -Wl,-O1 -L/usr/local/lib -Wl,--as-needed -o vim    -lSM -lICE -lXpm -lXt -lX11 -lXdmcp -lSM -lICE  -lm -ltinfo -lelf -lnsl   -lacl -lattr -lgpm -ldl     -lpython3.6m -lpthread -ldl -lutil -lm  -lruby24 -lpthread -lgmp -ldl -lcrypt -lm

My vim configuration

Answer 1

tldr; Add set re=2 into .vimrc prevents the issue on mac. I'm not sure why.

Answer 2

From :help 're':

                        *'regexpengine'* *'re'*
'regexpengine' 're' number  (default 0)
            global
    This selects the default regexp engine. |two-engines|
    The possible values are:
        0   automatic selection
        1   old engine
        2   NFA engine
    Note that when using the NFA engine and the pattern contains something
    that is not supported the pattern will not match.  This is only useful
    for debugging the regexp engine.
    Using automatic selection enables Vim to switch the engine, if the
    default engine becomes too costly.  E.g., when the NFA engine uses too
    many states.  This should prevent Vim from hanging on a combination of
    a complex pattern with long text.

This "old" engine supports everything but uses backtracking (which can be very slow in some patterns). The new engine is NFA-based, and may be slower or faster depending on the pattern. See :help two-engines. You can actually force a given pattern to use a different engine with the atom \%#=0 (or 1 or 2).

The best seems to be the default (0) which allows vim to decide.

You should probably talk to the yats people about why they "need" regexpengine=1...