Behaviour of BufEnter

Question

In neovim, open two different buffers as follows (using :vnew, for example):

*--------------*--------------*
|              |              |
|      1       |       2      |
|              |              |
*--------------*--------------*

In the first, run

:au BufEnter <buffer> :call feedkeys('ahello', 'n') 

In the second, run

:au BufEnter <buffer> :call feedkeys('ahola', 'n') 

Then, with the cursor in the second window, use e.g. :History from fzf.vim and cancel the search with <esc>.

Doing this on my machine, both autocommands are triggered on escaping the fzf window and, even more strange, they are executed in the same pane. Is this a bug, or am I not using autocommands correctly? End result:

*--------------*--------------*
|              |helloahola    |
|              |              |
|              |              |
*--------------*--------------*

Answer 1

I don't use fzf and use Vim instead of neovim. So I couldn't reproduce your scenario. Also I was not able to reproduce what @dedowsdi described in his comment.(See end of answer.)

But some general stuff around autocmd and feedkeys:

Assume we open Vim with three new files in split windows:

vim -O a.txt b.txt c.txt

Vim will open with three windows like this:

+--------------+--------------+--------------+
|      1       |      2       |      3       |
|    a.txt     |    b.txt     |    c.txt     |
|              |              |              |
+--------------+--------------+--------------+

Move to window 2 and execute :au BufEnter <buffer> :call feedkeys('ab.txt', 'n') and to window 3 and execute :au BufEnter <buffer> :call feedkeys('ac.txt', 'n') then back to window 1.

We now want to move to window 3 using two times <C-W>l. To avoid delays with manual input we use:

:normal ^Wl^Wl

(Note: ^W is entered as <C-V><C-W>.)

So the input queue is <C-W>l<C-W>l.

The first <C-W>l is consumed and the second window is activated. The autocmd kicks in and calls feedkeys.

Now the input queue is: <C-W>lab.txt

Now the other <C-W>l is consumed and the third window is activated. Again the autocmd kicks in and calls feedkeys.

Now the input queue is ab.txtac.txt.

This is processed and appends the text b.txtac.txt to the first line and leaves you in insert mode.

Conclusion:

Using feedkeys is tricky. You should exactly know where you are and what is happening around you. Combined with an autocmd this is even more tricky.

While your usage of autocmd is correct from a technical point of view, the combination with feedkeys might result in unexpected behavior.

---

Now a test based on the comment from @dedowski (using Vim):

Add an autocmd to 1, move to 3, open a help window, in your case, it should take full width. exit help window by q, you should see autocmd of 1 and 3 applied to 3.

Open Vim with three new files:

vim -O a.txt b.txt c.txt

we get:

+--------------+--------------+--------------+
|      1       |      2       |      3       |
|    a.txt     |    b.txt     |    c.txt     |
|              |              |              |
+--------------+--------------+--------------+

Change to the window showing c.txt and then open help with :help and we get:

+--------------+--------------+--------------+
|                   help                     |
|-----------------------------+--------------|
|      1       |      2       |      3       |
|    a.txt     |    b.txt     |    c.txt     |
+--------------+--------------+--------------+

Now execute:

:autocmd BufEnter * echomsg 'BufEnter ' . expand('%')

Then close the help window using :q and Vim will print

BufEnter a.txt
BufEnter c.txt

(You might need :messages to see both echos.)

Well -- that is unexpected. .