From b8c1b26f0ed49922e9101e8e1444e9b95321abcf Mon Sep 17 00:00:00 2001
From: Christian Brabandt <cb@256bit.org>
Date: Thu, 21 Apr 2016 09:11:22 +0200
Subject: [PATCH] don't throw error if bufferline is not installed

airline#extensions#load() tries to load all extensions,
the user has specified in g:airline_extensions.
However, if e.g. bufferline is requested to be loaded, but
is not installed, it will throw an error
E117: Unknown function: airline#extensions#bufferline#init

Therefore, catch E117 and show a warning.

closes #1127
---
 autoload/airline/extensions.vim | 6 +++++-
 autoload/airline/util.vim       | 6 ++++++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/autoload/airline/extensions.vim b/autoload/airline/extensions.vim
index 2970dc8e..5a499536 100644
--- a/autoload/airline/extensions.vim
+++ b/autoload/airline/extensions.vim
@@ -123,7 +123,11 @@ function! airline#extensions#load()
 
   if exists('g:airline_extensions')
     for ext in g:airline_extensions
-      call airline#extensions#{ext}#init(s:ext)
+      try
+        call airline#extensions#{ext}#init(s:ext)
+      catch /^Vim\%((\a\+)\)\=:E117/	" E117, function does not exist
+        call airline#util#warning("Extension '".ext."' not installed, ignoring!")
+      endtry
     endfor
     return
   endif
diff --git a/autoload/airline/util.vim b/autoload/airline/util.vim
index 65cf9068..f4525516 100644
--- a/autoload/airline/util.vim
+++ b/autoload/airline/util.vim
@@ -19,6 +19,12 @@ function! airline#util#append(text, minwidth)
   return empty(a:text) ? '' : prefix.g:airline_left_alt_sep.s:spc.a:text
 endfunction
 
+function! airline#util#warning(msg)
+  echohl WarningMsg
+  echomsg "airline: ".a:msg
+  echohl Normal
+endfunction
+
 function! airline#util#prepend(text, minwidth)
   if a:minwidth > 0 && winwidth(0) < a:minwidth
     return ''