Fix complex scenarios with definition, ordered, and unordered lists

[facelessuser]

Adds logic to the definition list indentation parser to be aware of unordered and ordered lists.

Fixes #918

[facelessuser]

I want to look into why coverage isn't like I expect. It seems the very minimum to get the tests to pass is to add ul and ol to the def list indention processor and li as well. With that said, none of the tests in the entire code base seem to exercise the create_item function. I want to try and force that area if possible to see what it actually does. Right now, I think it may not do what I think it does. And to be honest, it may never get executed at all, but I need to at least explore and understand what is supposed to trigger it.

[facelessuser]

@waylan I removed changes to def_list's create_item function. Nothing in the test suite exercises that code, not in the original, which def_list derives from, nor in the def_list one. I'm not even sure it can be triggered. Maybe it did at one time 🤷 .

Regardless, it makes no sense for me to alter code that can not be validated, isn't validated, and probably never actually run. I figure if a scenario comes up in the future that can actually trigger the code, and there is a problem, we can fix it then.

At this point, I think I'm done with this pull.

[waylan]

I did a quick search, and it appears the only place create_item is called is here:

markdown/markdown/blockprocessors.py

Lines 203 to 205 in be7ba7b

	else:
	self.create_item(sibling, block)
	self.parser.state.reset()

As it turns out, line 204 is listed among the lines with no test coverage, even for ol and ul lists. It appears that it is simply a safety net which was added at the end of a bunch of elif statements. My guess is it would never get called. Which begs the question: why was it ever added to the def_list extension?

In any event, thanks for the work on this.

[facelessuser]

It's possible that at some point it did get exercised. Whatever the case, whether just a safety net, or made that way over time, it doesn't seem necessary today 🙂.