Quoted terms are not detected as emphasis, in Japanese text

[piroor]

Description

Generally I can emphasize a quoted term in English like as:

$ echo 'before *"phrase"* after'  | build/src/cmark-gfm 
<p>before <em>&quot;phrase&quot;</em> after</p>

On the other hand, its translated version in Japanese is not emphasized same to above:

$ echo '前*「フレーズ」*後'  | build/src/cmark-gfm 
<p>前*「フレーズ」*後</p>

(Note:

• 前 means before
• 「 (`\u300c*) is an open quote
• フレーズ means phrase
• 」 (`\u300d*) is a close quote
• 後 means after

)

Both English version and Japanese version examples should be parsed in the same way.

Steps to reproduce

1. Clone the repository: git clone https://github.com/github/cmark.git
2. CD to the repository: cd cmark
3. Build the command line tool: make
4. Try to parse a emphasis for quoted term echo '前*「フレーズ」*後' | build/src/cmark-gfm

Expected result

<p>前<em>「フレーズ」</em>後</p>

Actual result

<p>前*「フレーズ」*後</p>

Details

It seems to be parsed based on the rule described at https://github.com/github/cmark/blob/master/test/spec.txt#L6346 :

This is not emphasis, because the opening `*` is preceded
by an alphanumeric and followed by punctuation, and hence
not part of a [left-flanking delimiter run]:

```````````````````````````````` example
a*"foo"*
.
<p>a*&quot;foo&quot;*</p>

However, in Japanese (and some other languages), terms are not separated with white spaces and emphasized quoted terms are generally written like as the example above.

[piroor]

「 is defined as a punctuation at https://github.com/github/cmark/blob/master/src/utf8.c#L255.

[kivikakk]

Hey, thanks for your issue. I believe this is an issue with the spec itself rather than our implementation, and I think there's already an open PR to the spec that should address this issue! Please see commonmark#208; it'd be helpful if you could add your voice to that PR to help it get momentum!

[kivikakk]

(Here's some more discussion context: https://talk.commonmark.org/t/emphasis-and-east-asian-text/2491)