Fix badly formed HTML sublists with Pandoc

fixSubLists.lua

--[[ fixSubLists.lua Fix badly formed HTML sublists in Pandoc

Apple Notes (via AppleScript) produces badly formed HTML 
for sublists: 

<ul>
	<li>Level 1 element 1</li>
	<ul>
		<li>Level 2 element 1</li>
		<li>Level 2 element 2</li>
	</ul>
	<li>Level 1 element 2</li>
</ul>

Pandoc corrects it by placing the sublist in its own list item:

<ul>
	<li>Level 1 element 1</li>
	<li>
		<ul>
			<li>Level 2 element 1</li>
			<li>Level 2 element 2</li>
		</ul>
	</li>
	<li>Level 1 element 2</li>
</ul>

This filter picks list items that consists of a single sublist and
insert them in the previous list element (if any) instead:

<ul>
	<li>Level 1 element 1
		<ul>
			<li>Level 2 element 1</li>
			<li>Level 2 element 2</li>
		</ul>
	</li>
	<li>Level 1 element 2</li>
</ul>

Usage

pandoc -L fixSubLists.lua -f html source.html -o out.html

]]

local function fixList(elem)
	local changed = false
	local newList = pandoc.List:new()
	
	local function isSubList(list)
		return #list == 1 
			and (list[1].t == 'BulletList' or list[1].t == 'OrderedList')
	end

	for _,item in ipairs(elem.c) do

		if #newList > 0 and isSubList(item) then
			-- append item's sublist to the last item of newList
			changed = true
			newList[#newList]:insert(item[1])
		else
			-- otherwise append item to newList
			newList:insert(item)
		end

	end

	if changed then
		elem.c = newList
	end

	return changed and elem or nil
end

return {{
	OrderedList = fixList,
	BulletList = fixList,
}}