Vim syntax group not stopping

Question

I recently upgraded to vim 8.2.0100 on Mac, and the markdown highlighting appears to have changed to be buggy.

Here is an example:

Normal syntax *Highlighting has started* Highlight continues
Highlight continues...

meaning the second * does not stop the highlighting on italics.

I see that echo &filetype returns markdown, and that :scriptnames includes (among many other files) /usr/local/Cellar/vim/8.2.0100/share/vim/vim82/syntax/markdown.vim

In the markdown syntax file, I see:

" start matches a non-whitespace character if preceeded by a * OR a * followed by a non-whitespace character.
" end   matches a non-whitespace character if preceeded by a * OR a * followed by a non-whitespace character
exe 'syn region markdownItalic matchgroup=markdownItalicDelimiter start="\S\@<=\*\|\*\S\@=" end="\S\@<=\*\|\*\S\@=" skip="\\*" contains=markdownLineStart,@Spell' . s:concealends

The comments are my own attempt to understand the syntax.

I have tried changing it a bunch, including just setting start="ic" and end="xc", but that doesn't work; I have the same problem where the start turns on the highlighting, but the end fails to turn it off.

This happens even with vim <filename> -u NONE (after I set the filetype to markdown and turn on syntax), meaning my .vimrc is not related

What am I missing in how to edit syntax files, or why doesn't the end get any matches?

Edit: I have noticed that it also does not work with Bold (**Bold**), and the bold will continue on through the rest of the document. Other segments, notably ```, do stop their changes.

Answer 1

Turns out it's just broke in 8.2.0100.

Here's the committed fix: https://github.com/tpope/vim-markdown/commit/e875717243fbea38189f5590a25a05809f03672b

The problem was with the skip="\\*". It was supposed to match the literal characters \*, so that you could display a literal * in markdown. However, \\ makes a literal \, so he was instead skipping any amount of \ characters, which included 0 backslash characters, which meant "skip everything". \\\* instead matches a literal \*, which is what you should write to display a literal * in your markdown output.

TL;DR: Change all instances of skip="\\*" in markdown.vim to skip="\\\*" and everything works.