From 449b4f1ed6084f81a1d0c2c1136cd242ec938625 Mon Sep 17 00:00:00 2001
From: Junegunn Choi <junegunn.c@gmail.com>
Date: Tue, 27 Jun 2017 17:44:12 +0900
Subject: [PATCH] Disallow using standard Vim plugin directory as plug home

Close #646
---
 README.md           | 4 +++-
 plug.vim            | 3 +++
 test/workflow.vader | 7 +++++++
 3 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/README.md b/README.md
index e9da75a..aae46b8 100644
--- a/README.md
+++ b/README.md
@@ -83,7 +83,9 @@ Add a vim-plug section to your `~/.vimrc` (or `~/.config/nvim/init.vim` for Neov
 #### Example
 
 ```vim
-" Specify a directory for plugins (for Neovim: ~/.local/share/nvim/plugged)
+" Specify a directory for plugins
+" - For Neovim: ~/.local/share/nvim/plugged
+" - Avoid using standard Vim directory names like 'plugin'
 call plug#begin('~/.vim/plugged')
 
 " Make sure you use single quotes
diff --git a/plug.vim b/plug.vim
index a7f1030..e0dc78f 100644
--- a/plug.vim
+++ b/plug.vim
@@ -121,6 +121,9 @@ function! plug#begin(...)
   else
     return s:err('Unable to determine plug home. Try calling plug#begin() with a path argument.')
   endif
+  if fnamemodify(home, ':t') ==# 'plugin' && fnamemodify(home, ':h') ==# s:first_rtp
+    return s:err('Invalid plug home. '.home.' is a standard Vim runtime path and is not allowed.')
+  endif
 
   let g:plug_home = home
   let g:plugs = {}
diff --git a/test/workflow.vader b/test/workflow.vader
index 78887ac..29826da 100644
--- a/test/workflow.vader
+++ b/test/workflow.vader
@@ -19,6 +19,13 @@ Execute (plug#begin() without path argument with empty &rtp):
   let &rtp = save_rtp
   unlet save_rtp
 
+Execute (Standard runtime path is not allowed):
+  redir => out
+  silent! AssertEqual 0, plug#begin(split(&rtp, ',')[0].'/plugin')
+  redir END
+  Log out
+  Assert stridx(out, 'Invalid plug home') >= 0
+
 Execute (plug#begin(path)):
   call plug#begin(g:temp_plugged.'/')
   Assert g:plug_home !~ '[/\\]$', 'Trailing / should be stripped from g:plug_home'