From ec486958ead7bf3e8375fd41db33ee3755f32102 Mon Sep 17 00:00:00 2001
From: Jaehwang Jerry Jung <tomtomjhj@gmail.com>
Date: Tue, 11 Jan 2022 02:31:57 +0900
Subject: [PATCH] Require no space after/before emphasis delimiter

Many markdown implementations require that `*` be not followed (resp.
preceded) by whitespace to open (resp. close) emphasis. For example,
commonmark.js, Markdown.pl, and pandoc compile the follow markdown

```markdown
a* asdf *a
```

to

```html
<p>a* asdf *a</p>
```

On the other hand, Python-Markdown allows whitespace:

```html
<p>a<em> asdf </em>a</p>
```

See https://johnmacfarlane.net/babelmark2/?normalize=1&text=a*+asdf+*a

Since variants of commonmark (including GFM) are prevalent these days,
it makes more sense to follow the first behavior.
---
 syntax/markdown.vim | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/syntax/markdown.vim b/syntax/markdown.vim
index 01d064d..e8e25d5 100644
--- a/syntax/markdown.vim
+++ b/syntax/markdown.vim
@@ -110,11 +110,11 @@ let s:concealends = ''
 if has('conceal') && get(g:, 'markdown_syntax_conceal', 1) == 1
   let s:concealends = ' concealends'
 endif
-exe 'syn region markdownItalic matchgroup=markdownItalicDelimiter start="\S\@<=\*\|\*\S\@=" end="\S\@<=\*\|\*\S\@=" skip="\\\*" contains=markdownLineStart,@Spell' . s:concealends
+exe 'syn region markdownItalic matchgroup=markdownItalicDelimiter start="\*\S\@=" end="\S\@<=\*" skip="\\\*" contains=markdownLineStart,@Spell' . s:concealends
 exe 'syn region markdownItalic matchgroup=markdownItalicDelimiter start="\w\@<!_\S\@=" end="\S\@<=_\w\@!" skip="\\_" contains=markdownLineStart,@Spell' . s:concealends
-exe 'syn region markdownBold matchgroup=markdownBoldDelimiter start="\S\@<=\*\*\|\*\*\S\@=" end="\S\@<=\*\*\|\*\*\S\@=" skip="\\\*" contains=markdownLineStart,markdownItalic,@Spell' . s:concealends
+exe 'syn region markdownBold matchgroup=markdownBoldDelimiter start="\*\*\S\@=" end="\S\@<=\*\*" skip="\\\*" contains=markdownLineStart,markdownItalic,@Spell' . s:concealends
 exe 'syn region markdownBold matchgroup=markdownBoldDelimiter start="\w\@<!__\S\@=" end="\S\@<=__\w\@!" skip="\\_" contains=markdownLineStart,markdownItalic,@Spell' . s:concealends
-exe 'syn region markdownBoldItalic matchgroup=markdownBoldItalicDelimiter start="\S\@<=\*\*\*\|\*\*\*\S\@=" end="\S\@<=\*\*\*\|\*\*\*\S\@=" skip="\\\*" contains=markdownLineStart,@Spell' . s:concealends
+exe 'syn region markdownBoldItalic matchgroup=markdownBoldItalicDelimiter start="\*\*\*\S\@=" end="\S\@<=\*\*\*" skip="\\\*" contains=markdownLineStart,@Spell' . s:concealends
 exe 'syn region markdownBoldItalic matchgroup=markdownBoldItalicDelimiter start="\w\@<!___\S\@=" end="\S\@<=___\w\@!" skip="\\_" contains=markdownLineStart,@Spell' . s:concealends
 
 syn region markdownCode matchgroup=markdownCodeDelimiter start="`" end="`" keepend contains=markdownLineStart