How do I keep folds when formatting (reindenting) the whole file?

Question

I do quite often use this mapping:

autocmd FileType cpp nnoremap <buffer> == :%!clang-format -style=file<cr>2g;zz

It reindents the whole file and returns the cursor to the last edit position.

Problem is, if I have folds, they get closed. All of them.

How do I keep each fold's state after this command? Some suggest saving a session, but this seems inefficient, and in my case I neither close the file nor leave vim.

Answer 1

Here is how I did it:

autocmd FileType cpp nnoremap <buffer> == :mkview<cr>:%!clang-format -style=file<cr>:loadview<cr>

Answer 2

EDIT: Here's something that might solve the issue. It's really a template of a possible solution (not actually tested).

function! ReindentMyCpp()
  mkview!
  execute 'normal! :nnoremap == :%!clang-format -style=file2g$' . "\r"
  execute 'normal zz'
  loadview
endfun

autocmd FileType cpp ReindentMyCpp()

BEFORE EDIT:

Here's some code that keeps the folds when you leave a buffer and restores it when you come back.

" save folds states in a file 'view'
set viewoptions=folds,cursor
autocmd BufWinLeave *.* mkview!
autocmd BufWinEnter *.* silent loadview 

This works well, and might somehow be adapted to your situation. It works of course if you have some autocmd that invokes mkview to save the fold's state before your own autocmd acts, and another that restores it afterwards.

I'm thinking you might want to define a function that does all three in a row (save the view in this way, do what your original autocmd did, then restore the view in this way), then have your autocmd invoke that function (as to save folds, do the indentation stuff, restore folds). I don't know if this will work for your problem, but it's probably worth a shot.