Vim: Conditionally use fugitive#statusline function in vimrc

Question

I use the same vimrc across many machines, some of which have fugitive.vim installed and some of which don't. I like including fugitive#statusline() in my statusline, but on machines that don't have the plugin installed this raises an error.

Is there a way to check for this function's existence before calling set statusline? I've tried using existsy, but it doesn't work for some reason (load order?)

if exists("*fugitive#statusline")
  set statusline=%<\ %f\ %{fugitive#statusline()} ... (other stuff)
endif

I've also tried silencing the error by prefixing the command with silent! but that doesn't seem to work either.

Answer 1

This one would be a shortcut:

set statusline+=%{exists('g:loaded_fugitive')?fugitive#statusline():''}

Answer 2

As fugitive does not define fugitive#statusline in an autoload directory it sadly can not be sniffed use silent! call / exists technique (Thank you @Christopher). There are however some alternatives:

• Put a ternary branch in your 'statusline' option as @tungd suggested.
• Set 'statusline' in an after/plugin file like @Christopher suggests. This solves the problem but means your statusline is defined in an rather unlikely place so it would probably be best to put in a nice comment in your ~/.vimrc file.
• Simply define the function in your ~/.vimrc file.

Example:

if !exists('*fugitive#statusline')
  function! fugitive#statusline()
      return ''
  endfunction
endif

• Another option is to use a Fugitive autocmd event that Fugitive defines. Note that this will only fire when Fugitive detects a git directory.

Put something like this in your ~/.vimrc file:

augroup fugitive_status
  autocmd!
  autocmd user Fugitive set statusline=%<\ %f\ %{fugitive#statusline()} ...
augroup END

Personally I think @tungd solution is the simplest. However just define a dummy function would be my next choice. Fugitive will override it if Fugitive is installed. The best part is this keeps your 'statusline' option neat and clean.