21 Mar 2019 , tagged: vim, tmux, ruby

Slow Ruby Syntax Highlighting in Vim

I recently switched back from MacVim to terminal (alacritty) Vim because I’m trying to step up my tmux game after reading the excellent tmux 2 book from the Pragmatic Bookshelf. But anyways, I noticed incredibly slow syntax highlighting for larger ruby files, so slow that editing code was almost impossible. After lots of searching and debugging I found it was the regular expression engine Vim uses by default in combination with the Ruby syntax highlighter.

The solution was to add this to my .vimrc:

set regexpengine=1

The vim docs state:

This selects the default regexp engine. |two-engines|
The possible values are:
  0	automatic selection
  1	old engine
  2	NFA engine

Furthermore the docs state that vim would automatically select the better engine, but that does not seem to work so well for the regular expressions in the syntax highlighter.

With re=1 vim flies again and thanks to my improved tmux skills I feel ever more productive!