define default statusline items with empty contents.

autoload/airline/init.vim

@@ -20,25 +20,6 @@ function! airline#init#bootstrap()
   call s:check_defined('g:airline_exclude_filetypes', [])
   call s:check_defined('g:airline_exclude_preview', 0)
 
-  call s:check_defined('g:airline_symbols', {})
-  call extend(g:airline_symbols, {
-        \ 'paste': get(g:, 'airline_paste_symbol', 'PASTE'),
-        \ 'readonly': get(g:, 'airline_readonly_symbol', get(g:, 'airline_powerline_fonts', 0) ? '' : 'RO'),
-        \ 'whitespace': get(g:, 'airline_powerline_fonts', 0) ? '✹' : '!',
-        \ 'linenr': get(g:, 'airline_linecolumn_prefix', get(g:, 'airline_powerline_fonts', 0) ? '' : ':' ),
-        \ 'branch': get(g:, 'airline_branch_prefix', get(g:, 'airline_powerline_fonts', 0) ? '' : ''),
-        \ }, 'keep')
-
-  call airline#parts#define_function('mode', 'airline#parts#mode')
-  call airline#parts#define_function('iminsert', 'airline#parts#iminsert')
-  call airline#parts#define_function('paste', 'airline#parts#paste')
-  call airline#parts#define('readonly', {
-        \ 'function': 'airline#parts#readonly',
-        \ 'highlight': 'airline_file',
-        \ })
-  call airline#parts#define_raw('file', '%f%m')
-  call airline#parts#define_raw('ffenc', '%{printf("%s%s",&fenc,strlen(&ff)>0?"[".&ff."]":"")}')
-
   call s:check_defined('g:airline_mode_map', {})
   call extend(g:airline_mode_map, {
         \ '__' : '------',
@@ -62,6 +43,27 @@ function! airline#init#bootstrap()
         \ '.*solarized.*': 'solarized',
         \ }, 'keep')
 
+  call s:check_defined('g:airline_symbols', {})
+  call extend(g:airline_symbols, {
+        \ 'paste': get(g:, 'airline_paste_symbol', 'PASTE'),
+        \ 'readonly': get(g:, 'airline_readonly_symbol', get(g:, 'airline_powerline_fonts', 0) ? '' : 'RO'),
+        \ 'whitespace': get(g:, 'airline_powerline_fonts', 0) ? '✹' : '!',
+        \ 'linenr': get(g:, 'airline_linecolumn_prefix', get(g:, 'airline_powerline_fonts', 0) ? '' : ':' ),
+        \ 'branch': get(g:, 'airline_branch_prefix', get(g:, 'airline_powerline_fonts', 0) ? '' : ''),
+        \ }, 'keep')
+
+  call airline#parts#define_function('mode', 'airline#parts#mode')
+  call airline#parts#define_function('iminsert', 'airline#parts#iminsert')
+  call airline#parts#define_function('paste', 'airline#parts#paste')
+  call airline#parts#define('readonly', {
+        \ 'function': 'airline#parts#readonly',
+        \ 'highlight': 'airline_file',
+        \ })
+  call airline#parts#define_raw('file', '%f%m')
+  call airline#parts#define_raw('ffenc', '%{printf("%s%s",&fenc,strlen(&ff)>0?"[".&ff."]":"")}')
+
+  call airline#parts#define_empty(['hunks', 'branch', 'tagbar', 'syntastic'])
+
   call airline#extensions#load()
 
   if !exists('g:airline_section_a')

autoload/airline/parts.vim

@@ -20,6 +20,12 @@ function! airline#parts#define_raw(key, raw)
   call airline#parts#define(a:key, { 'raw': a:raw })
 endfunction
 
+function! airline#parts#define_empty(keys)
+  for key in a:keys
+    call airline#parts#define_raw(key, '')
+  endfor
+endfunction
+
 function! airline#parts#get(key)
   return get(s:parts, a:key, {})
 endfunction

t/init.vim

@@ -22,9 +22,8 @@ describe 'init'
     Expect g:airline_section_a =~ 'iminsert'
   end
 
-  it 'section b should have hunks and branch'
-    Expect g:airline_section_b =~ 'hunks'
-    Expect g:airline_section_b =~ 'branch'
+  it 'section b should be blank because no extensions are installed'
+    Expect g:airline_section_b == ''
   end
 
   it 'section c should be file'
@@ -55,5 +54,12 @@ describe 'init'
       Expect g:airline_section_{s} == s
     endfor
   end
+
+  it 'all default statusline extensions should be blank'
+    Expect airline#parts#get('hunks').raw == ''
+    Expect airline#parts#get('branch').raw == ''
+    Expect airline#parts#get('tagbar').raw == ''
+    Expect airline#parts#get('syntastic').raw == ''
+  end
 end