How can I stop a system ftplugin file from overriding the keybindings from a plugin I manage via vim-plug?

Question

I am using the merlin plugin for Ocaml and right now I set the runtimepath by hand, as per their installation instructions:

call plug#begin('~/.vim/plugins')
  "other plugins go here...
call plug#end()

set rtp+=/home/hugo/.opam/4.02.3/share/merlin/vim

I want to change this so that merlin is managed by vim-plug for consistency and because of vim-plug's lazy-loading feature. I tried doing the following but now my ocaml keybindings are broken:

call plug#begin('~/.vim/plugins')
  "other plugins go here...

  Plug '/home/hugo/.opam/4.02.3/share/merlin/vim'
call plug#end()

Apparently, there is an /usr/share/vim/vim74/ftplugin/ocaml.vim file in my system that overrides some of the keybindings that are automatically defined by merlin. When I was setting the runtimepath by hand the merlin directory appeared last in the runtimepath list (as seen via :echo &rtp), which seemingly causes merlin to load last but when I use vim-plug the merlin dir shows up before /usr/share/vim/vim74 and the keybinds from the system file have priority.

What is the best way to solve this conflict? Should I look for a way to disable the unwanted ftplugin file that comes installed in my system? Should I redefine all the broken keybindings by hand? Or is there something else I can do?

Answer 1

Look at the top of $VIMRUNTIME/ftplugin/ocaml.vim -- you'll see some lines that say:

if exists("b:did_ftplugin")
  finish
endif    

So, put in your personal

$HOME/.vim/ftplugin/ocaml.vim

the line

let b:did_ftplugin= 1

This will effectively prevent the system ocaml plugin from loading.