Lines inside fenced code blocks that start with an octothorpe are interpreted as headers and break folding

[rpdelaney]

This looks very much along the lines of #1. Possibly related to #6 also (but I kinda doubt it).

Using vim-markdown-folding with vim-plug, on 3f35acf. I'm observing a problem when editing this file I'm working on.

Looks like this:

#     Pre-OS prep                             [17 lines]-----------------------------------------------------------------------------------
##    Installation media                      [13 lines]-----------------------------------------------------------------------------------
##    Create partitions                       [4 lines]------------------------------------------------------------------------------------
#     gdisk /dev/nvme0n1                      [7 lines]------------------------------------------------------------------------------------
##    Create LUKS container                   [4 lines]------------------------------------------------------------------------------------
#     cryptsetup luksFormat --type luks1 --use-random --hash whirlpool --iter-time 5000 /dev/nvme0n1p2 [4 lines]---------------------------
##    O/S Filesystem                          [7 lines]------------------------------------------------------------------------------------
###   Create and mount LVM volumes            [6 lines]------------------------------------------------------------------------------------
# vgcreate volgroup0 /dev/mapper/cryptlvm
# lvcreate volgroup0 -L 32G -n lvswap
#     lvcreate volgroup0 -l 100%FREE -n lvroot [5 lines]-----------------------------------------------------------------------------------
###   Create btrfs filesystem                 [4 lines]------------------------------------------------------------------------------------
# mkfs.btrfs -L root /dev/volgroup0/lvroot
# mkswap -L swap /dev/volgroup0/lvswap
#     swapon -L swap                          [56 lines]-----------------------------------------------------------------------------------
##    O/S                                     [4 lines]------------------------------------------------------------------------------------

I would expect something more like this (maybe with different counts of folded lines):

#     Pre-OS prep                             [17 lines]-----------------------------------------------------------------------------------
##    Installation media                      [13 lines]-----------------------------------------------------------------------------------
##    Create partitions                       [4 lines]------------------------------------------------------------------------------------
##    Create LUKS container                   [4 lines]------------------------------------------------------------------------------------
##    O/S Filesystem                          [7 lines]------------------------------------------------------------------------------------
###   Create and mount LVM volumes            [6 lines]------------------------------------------------------------------------------------
###   Create btrfs filesystem                 [4 lines]------------------------------------------------------------------------------------
##    O/S                                     [4 lines]------------------------------------------------------------------------------------

[masukomi]

My apologies for the delay.

Thanks for the nice writeup and use-case @rpdelaney

I'll try and set aside some time to look at this. If you come up with a PR that addresses it I'll happily merge it.

[masukomi]

quick note for future me:

As the title suggests, the problem is essentially that it's not ignoring headings contained in code fences.

eg

```
# cryptsetup luksFormat --type luks1 --use-random --hash whirlpool --iter-time 5000 /dev/nvme0n1p2
```

[wesrer]

@masukomi Any progress on this?

[noperator]

Also experiencing this issue and would love a fix! Thanks for a great plugin @masukomi 🙂

[masukomi]

@wesrer just haven't gotten around to working on this. Will happily accept PRs (cc @noperator ) ;)

[noperator]

Strangely, I'm encountering this issue a bit inconsistently. I tried to reproduce @rpdelaney's example above by downloading the file as is, and opening it in vim.

wget https://raw.githubusercontent.com/rpdelaney/iris-setup/a73f04ab1d0d0cc587d40893af2bf48c7eb81ba7/PRE_OS.md
vim PRE_OS.md

Here's what I'm seeing:

#     Pre-OS prep                             [17 lines]-----------------------
##    Installation media                      [13 lines]-----------------------
##    Create partitions                       [12 lines]-----------------------
##    Create LUKS container                   [9 lines]------------------------
##    O/S Filesystem                          [7 lines]------------------------
###   Create and mount LVM volumes            [14 lines]-----------------------
###   Create btrfs filesystem                 [63 lines]-----------------------
##    O/S                                     [4 lines]------------------------

I'll report back here if I can reproduce an octothorpe within fenced code blocks that breaks folding.

[noperator]

I noticed that wherever leading octothorpes inside fenced code blocks were interpreted by this plugin as a header, those lines were also highlighted as headers—i.e., for some reason, Vim's included syntax highlighting wasn't recognizing those lines as being inside of a code block. That's likely the root issue here since this plugin's folding.vim, in turn, relies on the aforementioned syntax highlighting to determine whether a given line is inside of a code block or not:

vim-markdown-folding/after/ftplugin/markdown/folding.vim

Lines 67 to 76 in 3f35acf

	function! LineIsFenced(lnum)
	if exists("b:current_syntax") && b:current_syntax ==# 'markdown'
	" It's cheap to check if the current line has 'markdownCode' syntax group
	return HasSyntaxGroup(a:lnum, '\vmarkdown(Code|Highlight)')
	else
	" Using searchpairpos() is expensive, so only do it if syntax highlighting
	" is not enabled
	return s:HasSurroundingFencemarks(a:lnum)
	endif
	endfunction

I think I solved this issue (in my case, at least) by following some guidance from tpope/vim-markdown (Vim's included syntax highlighting):

Syntax highlight is synchronized in 50 lines. It may cause collapsed highlighting at large fenced code block. In the case, please set larger value in your vimrc:

let g:markdown_minlines = 100

Note that setting too large value may cause bad performance on highlighting.

I kept increasing g:markdown_minlines until this problem went away (i.e., until the folded headers looked right), settling at 1000 with no recognizable performance issues. Here's my .vimrc for your reference; masukomi/vim-markdown-folding is the only plugin I'm using, installed with Vim's native package loading.