On: Vim Tips For Intermediate Users

[Tiksi]

Vim actually has a built in debugger and a couple extra features for debugging:

http://inlehmansterms.net/2014/10/31/debugging-vim/

http://vimdoc.sourceforge.net/htmldoc/repeat.html#debug-mode ( or :h debug-mode )

I recall there being a few gotchas last time I used debug mode and they're mentioned in the doc, but unfortunately I don't quite remember what they were.