Vim Powerline with Syntastic segment

Question

Most of these instruction come from this pull request (451) for powerline.

This pull request adds a syntactic segment to powerline. Since the segment isn't merged into the main powerline tree you need to preform the patches by hand. Thankfully you only need to modify three files. (+ means add the line/ - mean remove line). Look at the pull request for a colored diff.

File: powerline/config_files/colorschemes/vim/default.json (Line 28)

     "line_current_symbol": { "fg": "gray1", "bg": "gray10" },
     "virtcol_current_gradient": { "fg": "dark_GREEN_Orange_red", "bg": "gray10" },
     "col_current": { "fg": "gray6", "bg": "gray10" },
-    "modified_buffers": { "fg": "brightyellow", "bg": "gray2" }
+    "modified_buffers": { "fg": "brightyellow", "bg": "gray2" },
+    "syntastic_segment": { "fg": "brightestred", "bg": "gray2", "attr": ["bold"] }
   },
   "mode_translations": {
     "nc": {

File: powerline/config_files/colorschemes/vim/default.json (Line 68)

       "groups": {
         "mode": { "fg": "darkestcyan", "bg": "white", "attr": ["bold"] },
         "background:divider": { "fg": "darkcyan", "bg": "darkestblue" },
-        "branch:divider": { "fg": "darkcyan", "bg": "darkblue" }
+        "branch:divider": { "fg": "darkcyan", "bg": "darkblue" },
+        "syntastic_segment": { "fg": "white", "bg": "darkestblue", "attr": ["bold"] }
       }
     },
     "v": {

File: powerline/config_files/colorschemes/vim/solarized.json (Line 27)

     "line_current":             { "fg": "gray13", "bg": "lightyellow", "attr": ["bold"] },
     "line_current_symbol":      { "fg": "gray13", "bg": "lightyellow" },
     "virtcol_current_gradient": { "fg": "GREEN_Orange_red", "bg": "gray10" },
-    "col_current":              { "fg": "azure4", "bg": "lightyellow" }
+    "col_current":              { "fg": "azure4", "bg": "lightyellow" },
+    "syntastic_segment":        { "fg": "red", "bg": "royalblue5", "attr": ["bold"] }
   },
   "mode_translations": {
     "nc": {

File: powerline/config_files/colorschemes/vim/solarized.json (Line 65)

         "line_percent_gradient":  { "fg": "oldlace", "bg": "gray61" },
         "line_current":           { "fg": "gray13", "bg": "oldlace", "attr": ["bold"] },
         "line_current_symbol":    { "fg": "gray13", "bg": "oldlace" },
-        "col_current":            { "fg": "azure4", "bg": "oldlace" }
+        "col_current":            { "fg": "azure4", "bg": "oldlace" },
+        "syntastic_segment":      { "fg": "lightyellow", "bg": "darkgreencopper", "attr": ["bold"] }
       }
     },
     "v": {

File: powerline/segments/vim.py (Line 23)

   'expand': vim_get_func('expand', rettype=str),
   'bufnr': vim_get_func('bufnr', rettype=int),
   'line2byte': vim_get_func('line2byte', rettype=int),
+  'exists': vim_get_func('exists', rettype=int),
 }

 vim_modes = {

At the end of powerline/segments/vim.py add the following function. (Make sure you use tabs to indent the function. You are modifying a python file indentation matters)

@window_cached
def syntastic_segment(pl):
    '''Return the syntastic statusline flag
    '''
    if int(vim_funcs['exists']('*SyntasticStatuslineFlag')) > 0:
        syntastic_flag_func = vim_get_func('SyntasticStatuslineFlag', rettype=str)
        return [{
            'contents': str(syntastic_flag_func()),
        }]
    else:
        return None

After all these changes are made you need to now turn on the segment. One way to do this is to edit the config file ~/.config/powerline/themes/vim/default.json

In the section segments: place the following in either the right or the left sections.

{
    "name": "syntastic_segment",
    "before": " "
},

After all of these changes you should now be able to see the syntastic error output on the power line segment.

Troubleshooting:

if you introduce parse errors into the json you can start vim up with vim --noplugin to start vim without plugins to powerline doesn't try and parse the file.
Make sure the commas for the json are in the right places.
Make sure you used tabs and not spaces in the python files when editing them.