Close all NERDtree instances on VIM exit

Question

If you have any NERDTree instances open when you quit VIM then when you open your session again you get a number of errors:

Error detected while processing BufLeave Autocommands for "NERD_tree_*":
E121: Undefined variable: b:NERDTree
Error detected while processing WinLeave Autocommands for "NERD_tree_*":

Error detected while processing BufLeave Autocommands for "NERD_tree_*":
E121: Undefined variable: b:NERDTree
Error detected while processing WinLeave Autocommands for "NERD_tree_*":

I am trying to execute :tabdo NERDTreeClose automatically when vim exits (eg with qa or wqa or qa! etc)

I am adding:

autocmd VimLeave * tabdo NERDTreeClose<CR> or autocmd VimLeave * :tabdo NERDTreeClose<CR>

with or without <CR> at the end but I can't make it work.

Any suggestions?

Answer 1

I have previously encountered the exact same issue with the combination of creating (and reentering) [neo]Vim -sessions and multiple NERDTree -instances.

My solution, which might not be the precise answer that you are looking for due to the reason that will be explained later, was to first close all NERDTree instances before creating or updating the [neo]Vim -Session for later usage. What you have been trying so far with the tabdo is thus a few "stages" too late, as the triggering event for auto-command is VimLeave .

My primary suggestion (also my personal resort) is to create a quick key-bind that performs the two procedures I stated above combined with a quick save-all in serial:

cnoremap W tabdo NERDTreeClose <bar> wa <bar> mksession! ~/.vim/My_Session.vim

which can be comfortably remembered as the bigger brother of the default w in commandline-mode for saving (a single buffer).

The one caveat of this method is that all instances of NERDTree will be closed when reentering the session saved from above. This, however, can be somewhat remedied by calling NERDTreeToggle with VimEnter as the triggering event for autocmd .

If you insist on utilising autocmd for this, I would suggest putting the two procedures enlisted above into a function and use autocmd to call that function (with the [neo]Vim command: call) upon VimLeave just like you have tried before, of course under the assumption that you feel compelled to save the session during every exit. I personally do not endorse this, as instances were abundant where I would quickly fire up [neo]Vim for a quick note of something inconsequential and swiftly exit, which certainly does not require that the session be saved.

As a sidenote: the syntax of autocmd:

:au[tocmd] [group] {event} {pat} [++once] [++nested] {cmd}

thus, substitute cmd with a command directly, ie, the prefixing colon as you have tried in your original post is a malpractice.