When I started using Ubuntu 16.04 LTS, I was overall happy with it, except for one thing. Its Vim installation behaved strangely, to say the least. On the first look, it tried to be user-friendly: it automatically provided pop-up prompts when I typed something. It also tried to be smart, e.g. path candidates were provided when I was typing a path. Sounds great? Er . . . actually no, at least not to experienced Vim users.
The problem with it was that it was far too intrusive. If what I was typing had at least one autocompletion candidate when I typed Enter, the first candidate was chosen, instead of inserting a newline. What if I really meant to insert a newline? Oh, I had to press Ctrl-E to cancel the autocompletion first (by the way, this is a Vim command I had to do a Google search to find; before that I used Esc followed by o).
Now think about it: Which thing does an advanced user do more often, consulting the screen and choosing an autocompletion candidate, or continuously typing onto newlines, probably without even looking at the screen? When we do need to autocomplete, we all know well how to invoke autocompletion by Ctrl-P and Ctrl-N.
I tolerated this behaviour for a few months. Today I decided I really needed to get rid of it. I first searched the web, but did not see any obvious results. After a few experiments, I checked the /usr/share/vim/vim74/plugin directory, and immediately found a likely suspect—acp.vim! It turned out to be the AutoComplPop plugin. After checking its code, I simply inserted the following line into my .vimrc file:
Problem solved, and I am feeling happy again!
I do not know whether Canonical thought carefully about enabling this plugin by default, which might help new users but hurt experienced users. Maybe they thought experienced users could find a way out. I guess it might be true, but I wasted 20 minutes finding the solution, and then spent another hour writing up this article. . . . I do hope this article can help another disgruntled Vim user on Ubuntu. 🙂