From 4878fab120117529b32f944b56b517127b2b8b0c Mon Sep 17 00:00:00 2001
From: Kevin Chen <chenaren@gmail.com>
Date: Fri, 21 Nov 2014 23:39:39 +0800
Subject: [PATCH] Add a virtualenv fallback when vim-virtualenv is not
 presented

---
 autoload/airline/extensions.vim            | 2 +-
 autoload/airline/extensions/virtualenv.vim | 9 +++++++--
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/autoload/airline/extensions.vim b/autoload/airline/extensions.vim
index 1738f62..66a1c34 100644
--- a/autoload/airline/extensions.vim
+++ b/autoload/airline/extensions.vim
@@ -178,7 +178,7 @@ function! airline#extensions#load()
     call airline#extensions#bufferline#init(s:ext)
   endif
 
-  if get(g:, 'virtualenv_loaded', 0) && get(g:, 'airline#extensions#virtualenv#enabled', 1)
+  if isdirectory($VIRTUAL_ENV) && get(g:, 'airline#extensions#virtualenv#enabled', 1)
     call airline#extensions#virtualenv#init(s:ext)
   endif
 
diff --git a/autoload/airline/extensions/virtualenv.vim b/autoload/airline/extensions/virtualenv.vim
index f070c47..27f847e 100644
--- a/autoload/airline/extensions/virtualenv.vim
+++ b/autoload/airline/extensions/virtualenv.vim
@@ -1,7 +1,7 @@
 " MIT License. Copyright (c) 2013-2014 Bailey Ling.
 " vim: et ts=2 sts=2 sw=2
 
-if !get(g:, 'virtualenv_loaded', 0)
+if !isdirectory($VIRTUAL_ENV)
   finish
 endif
 
@@ -13,8 +13,13 @@ endfunction
 
 function! airline#extensions#virtualenv#apply(...)
   if &filetype =~ "python"
+    if get(g:, 'virtualenv_loaded', 0)
+      let statusline = virtualenv#statusline()
+    else
+      let statusline = fnamemodify($VIRTUAL_ENV, ':t')
+    endif
     call airline#extensions#append_to_section('x',
-          \ s:spc.g:airline_right_alt_sep.s:spc.'%{virtualenv#statusline()}')
+          \ s:spc.g:airline_right_alt_sep.s:spc.statusline)
   endif
 endfunction