much smarter handling of separators (#204).

autoload/airline/init.vim

@@ -58,6 +58,7 @@ function! airline#init#bootstrap()
   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_function('filetype', 'airline#parts#filetype')
   call airline#parts#define('readonly', {
         \ 'function': 'airline#parts#readonly',
         \ 'highlight': 'airline_file',
@@ -83,7 +84,7 @@ function! airline#init#sections()
     let g:airline_section_gutter = airline#section#create([' ', 'readonly', '%='])
   endif
   if !exists('g:airline_section_x')
-    let g:airline_section_x = airline#section#create_right(['tagbar', '%{&filetype}'])
+    let g:airline_section_x = airline#section#create_right(['tagbar', 'filetype'])
   endif
   if !exists('g:airline_section_y')
     let g:airline_section_y = airline#section#create_right(['ffenc'])

autoload/airline/parts.vim

@@ -57,3 +57,7 @@ function! airline#parts#readonly()
   return &readonly ? g:airline_symbols.readonly : ''
 endfunction
 
+function! airline#parts#filetype()
+  return &filetype
+endfunction
+

autoload/airline/section.vim

@@ -3,8 +3,10 @@
 
 call airline#init#bootstrap()
 
-function! s:get_val(key, append)
-  let part = airline#parts#get(a:key)
+function! s:create(parts, append)
+  let _ = ''
+  for idx in range(len(a:parts))
+    let part = airline#parts#get(a:parts[idx])
 
     let val = ''
     if exists('part.highlight')
@@ -15,42 +17,45 @@ function! s:get_val(key, append)
       let func = (part.function).'()'
     elseif exists('part.text')
       let func = '"'.(part.text).'"'
-  elseif exists('part.raw')
-    return val.(part.raw)
     else
-    return a:key
+      if a:append > 0 && idx != 0
+        let val .= ' '.g:airline_left_alt_sep.' '
+      endif
+      if a:append < 0 && idx != 0
+        let val = ' '.g:airline_right_alt_sep.' '.val
+      endif
+      if exists('part.raw')
+        let _ .= val.(part.raw)
+        continue
+      else
+        let _ .= val.a:parts[idx]
+        continue
+      endif
     endif
 
     let minwidth = get(part, 'minwidth', 0)
 
-  if a:append > 0
+    if a:append > 0 && idx != 0
       let val .= printf('%%{airline#util#append(%s,%s)}', func, minwidth)
-  elseif a:append < 0
+    elseif a:append < 0 && idx != len(a:parts) - 1
       let val .= printf('%%{airline#util#prepend(%s,%s)}', func, minwidth)
     else
       let val .= printf('%%{airline#util#wrap(%s,%s)}', func, minwidth)
     endif
-  return val
+    let _ .= val
+  endfor
+  return _
 endfunction
 
 function! airline#section#create(parts)
-  return join(map(a:parts, 's:get_val(v:val, 0)'), '')
+  return s:create(a:parts, 0)
 endfunction
 
 function! airline#section#create_left(parts)
-  let _ = s:get_val(a:parts[0], 0)
-  for i in range(1, len(a:parts) - 1)
-    let _ .= s:get_val(a:parts[i], 1)
-  endfor
-  return _
+  return s:create(a:parts, 1)
 endfunction
 
 function! airline#section#create_right(parts)
-  let _ = ''
-  for i in range(0, len(a:parts) - 2)
-    let _ .= s:get_val(a:parts[i], -1)
-  endfor
-  let _ .= s:get_val(a:parts[-1], 0)
-  return _
+  return s:create(a:parts, -1)
 endfunction
 

doc/airline.txt

@@ -319,6 +319,12 @@ Note: The use of `VimEnter` is important, because most extensions are lazily
 loaded, so we must give them a chance to define their parts before we can use
 them.
 
+Note: The `airline#section#create` function and friends will do its best to
+create a section with the appropriate separators, but it only works for
+function and text parts. Special |statusline| items like %f or raw parts will
+not work as it is not possible to inspect their widths/contents before
+rendering to the statusline.
+
 ==============================================================================
 FUNCREFS                                                  *airline-funcrefs*
 

t/section.vim

@@ -34,7 +34,7 @@ describe 'section'
     Expect s == '%#hlgroup#hello'
   end
 
-  it 'should parse out a section from the vimrc'
+  it 'should parse out a section from the distro'
     let s = airline#section#create(['whitespace'])
     Expect s =~ 'airline#extensions#whitespace#check'
   end
@@ -43,5 +43,16 @@ describe 'section'
     let s = airline#section#create(['asdf', 'func'])
     Expect s == 'asdf%{airline#util#wrap(SectionSpec(),0)}'
   end
+
+  it 'should force add separators for raw and missing keys'
+    let s = airline#section#create_left(['asdf', 'raw'])
+    Expect s == 'asdf > raw'
+    let s = airline#section#create_left(['asdf', 'aaaa', 'raw'])
+    Expect s == 'asdf > aaaa > raw'
+    let s = airline#section#create_right(['raw', '%f'])
+    Expect s == 'raw < %f'
+    let s = airline#section#create_right(['%t', 'asdf', '%{getcwd()}'])
+    Expect s == '%t < asdf < %{getcwd()}'
+  end
 end