getting the fold state of lines in nested folds

Question

vim provides the methods foldclosed() and foldclosedend() to get the first and last line of a closed fold. The problem is: It does not respect nested folds.

For example this file:

line 1
  line 2
  line 3
    line 4
    line 5
  line 6
line 7

has manual folds:

1. line 1 - 6
2. line 3 - 5

All of them are closed (first the second, inner, fold, then the first, outer, fold). When calling foldclosed(4) and foldclosedend(4) I would expect to get the values 3 and 5, since this is the fold line 4 is contained in. However it returns 1 and 6 for all lines except 7 (which is not in a fold).

Is there a way to get the fold state of each fold that respects nested folds? I expect something like what mkview does, which remembers the correct nested folds:

3,5fold
1,6fold
1
normal! zo
3
normal! zc
1
normal! zc

Answer 1

There is no builtin vim-script function which provides that. But you can make your own using builtin foldclosed foldclosedend and foldlevel functions. Here is a snippet I made:

function NestFoldClosed(lnum)
  let b = foldlevel(a:lnum)
  let lnum = a:lnum
  if b > 1 
    let temp = b
    " find the previous line that has foldlevel one less than the current line
    while(temp == b)
      let lnum = lnum - 1
      let temp = foldlevel(lnum)
    endwhile
    return lnum + 1
  endif
  return foldclosed(a:lnum)
endfunction

function NestFoldClosedEnd(lnum)
  let b = foldlevel(a:lnum)
  let lnum = a:lnum
  if b > 1 
    let temp = b
    " find the next line that has foldlevel one less than the current line
    while(temp == b)
      let lnum = lnum + 1
      let temp = foldlevel(lnum)
    endwhile
    return lnum - 1
  endif
  return foldclosed(a:lnum)
endfunction

Now if you do the following and call NestFoldClosed(4) and NestFoldClosedEnd(4) you will get the correct line numbers.

:3,5fold 
:1,6fold 
:1 
:normal! zo 
:3 
:normal! zc 
:1 
:normal! zc