Setting foldmethod=expr when re-sourcing vimrc?

Question

I have the following on my vimrc file to handle custom folding:

" ++ Folding                                                                    
 set foldenable                      " enable folding                            
 set foldmethod=syntax               " global folding method                
 set foldlevelstart=1                " folds with level 1 aren't closed 

augroup FileTypeVim                                                                                                                                                 
   autocmd!                                                                    
   autocmd FileType vim setlocal foldmethod=expr foldexpr=VimrcFold()          
augroup END

When I open my vimrc it works perfectly fine. However, if I re-source my vimrc the foldmethod is set to syntax (global) instead of expr (specific for filetype vim). What do I have to specify in order to keep the vimrc with expr foldmethod? I suspect it has to be with BufType rather than FileType but I am not sure how to deal with that.

Answer 1

You can do that with a modeline and an autocommand. E.g.

The modeline :

" vim: set sw=4 ts=4 sts=4 et tw=78 foldmarker={,} foldlevel=0 foldmethod=marker spell:

With this modeline I can fold my vimrc based on {} pairs.

The autocommands :

augroup FileTypeVim
   autocmd!
   " Source your vimrc on save
   autocmd! BufWritePost .vimrc source %
   " Apply modeline option after re-openning the vimrc file (that is after sourcing it)
   autocmd! BufWritePost .vimrc set modeline | doautocmd BufRead
augroup END

References :

• https://stackoverflow.com/questions/24221294/vim-read-modeline-after-opening-the-file
• http://vim.wikia.com/wiki/Modeline_magic

Answer 2

When resourcing your .vimrc you will overwrite your current foldmethod setting and reset it to "syntax". The autocommand won't trigger, since by that time, the filetype has already been set.

One way around it, would be to check your current foldmethod and only set it, if it set to manual, e.g. like this:

if &l:fdm is# 'manual'
    let &fdm='syntax'
 endif

This checks the local foldmethod setting for the current buffer and only sets the global option, if the local value is at the default value of 'manual' (assuming it had not been set).