Weird behavior of `autocmd BufEnter * call ncm2#enable_for_buffer()` after updating plugin

OS

MacOS 10.13.4

neovim :version output

0.3.1

Minimal vimrc for reproducing the issue

Plug 'roxma/nvim-yarp'
Plug 'ncm2/ncm2-tagprefix'
Plug 'scrooloose/nerdtree'

autocmd BufEnter * call ncm2#enable_for_buffer()

reproduce the issue

With the recently commits of ncm2, it seems like autocmd BufEnter * call ncm2#enable_for_buffer() cause some quirks in vim quickfix: whenever I open fzf, ag or perform :PlugUpdate, vim window doesn’t show the result until I hit some keys to get it to update:

the status will display updating... forever, when I hit j or k it gets updated like this:

The same happen for ag and fzf window, they all show blank window:

I have to hit a random key to get this:

Remove autocmd BufEnter * call ncm2#enable_for_buffer() results with no weird errors.

[clason]

I get the same behavior also on macOS 10.13.6 and Linux. Bisecting shows that 6f1e1e9ad80a48b6fa67fa565756518ec95e6670 broke this. (Probably some special casing of quickfix-like buffers is required in the python core.)

Workaround (at least for the plugin updating; I don’t use ag or fzf) from https://github.com/ncm2/ncm2/issues/39#issuecomment-409692887: Replace BufEnter with InsertEnter in your init.vim (which seems like a reasonable default configuration, by the way, since you don’t need autocomplete before you start typing).

[huyvohcmc]

@roxma Yes it is, thanks so much.