Dash-separated long list items rendered as sublist

まず、--to commonmark --width 80 を使用して cmark 0.29.0 で問題を再現し、その後、報告に示されているように出力を cmark にもう一度通します。リスト項目を折り返す際にリンクの後のダッシュがどのように処理されるかを追跡し、ラウンドトリップによって説明が同じリスト項目内に保持され、サブリストが作成されないことを確認します。

Here is a Markdown file with a list of very long items:

❯ cat ./dash-separated-link-list.md
- [Link 1](#link-1) - Description of line 1.
- [Link 2](#link-2) - A very long description for the second link in the list. That description is more than 80 characters wide.
- [This is a very long title, pointing to an awesome article on incredible stuff we're not used to see everyday](#link-3) - Line #3's description.
- [Link number three](#this-is-a-very-long-url-that-is-pointing-to-a-really-really-great-website) - Fourth description.

It cleanly renders into a list of 4 items:

❯ /System/Volumes/Data/usr/local/opt/cmark/bin/cmark ./dash-separated-link-list.md
<ul>
<li><a href="#link-1">Link 1</a> - Description of line 1.</li>
<li><a href="#link-2">Link 2</a> - A very long description for the second link in the list. That description is more than 80 characters wide.</li>
<li><a href="#link-3">This is a very long title, pointing to an awesome article on incredible stuff we're not used to see everyday</a> - Line #3's description.</li>
<li><a href="#this-is-a-very-long-url-that-is-pointing-to-a-really-really-great-website">Link number three</a> - Fourth description.</li>
</ul>

Now if I try to tidy up the original markdown into a 80-chars wide format, I get the following:

❯ /System/Volumes/Data/usr/local/opt/cmark/bin/cmark --to commonmark --width 80 ./dash-separated-link-list.md
  - [Link 1](#link-1) - Description of line 1.
  - [Link 2](#link-2) - A very long description for the second link in the list.
    That description is more than 80 characters wide.
  - [This is a very long title, pointing to an awesome article on incredible
    stuff we're not used to see everyday](#link-3) - Line \#3's description.
  - [Link number
    three](#this-is-a-very-long-url-that-is-pointing-to-a-really-really-great-website)
    - Fourth description.

Which renders into a list with an additional sub-list item:

❯ /System/Volumes/Data/usr/local/opt/cmark/bin/cmark --to commonmark --width 80 ./dash-separated-link-list.md | /System/Volumes/Data/usr/local/opt/cmark/bin/cmark
<ul>
<li><a href="#link-1">Link 1</a> - Description of line 1.</li>
<li><a href="#link-2">Link 2</a> - A very long description for the second link in the list.
That description is more than 80 characters wide.</li>
<li><a href="#link-3">This is a very long title, pointing to an awesome article on incredible
stuff we're not used to see everyday</a> - Line #3's description.</li>
<li><a href="#this-is-a-very-long-url-that-is-pointing-to-a-really-really-great-website">Link number
three</a>
<ul>
<li>Fourth description.</li>
</ul>
</li>
</ul>

This is due to an edge-case that is splitting an item content just before the dash located right after the link.

This bug has been reported first to the pandoc project at: https://github.com/jgm/pandoc/issues/6497 . An interesting thing here is that the previous implementation was supporting this edge case while the new one based on cmark does not.

For reference, here the version of cmark I'm using, installed with brew on macOS Catalina:

❯ brew install cmark
(...)
==> Downloading https://homebrew.bintray.com/bottles/cmark-0.29.0_1.catalina.bottle.tar.gz
==> Downloading from https://akamai.bintray.com/3a/3af95418f96f4b0cec4bd76abaab312f3caf4cea591f38d3b725f15068d06491?__gda__=exp=1593691219~hmac=7f6c15036b995f36438e934f5bd44ec8
######################################################################## 100.0%
==> Pouring cmark-0.29.0_1.catalina.bottle.tar.gz
🍺  /usr/local/Cellar/cmark/0.29.0_1: 17 files, 724.9KB

❯ /System/Volumes/Data/usr/local/opt/cmark/bin/cmark --version
cmark 0.29.0 - CommonMark converter
(C) 2014-2016 John MacFarlane

This bug can also be reproduced with the cmark-gfm formulae provided by brew:

❯ /System/Volumes/Data/usr/local/opt/cmark-gfm/bin/cmark-gfm --version
cmark-gfm 0.29.0.gfm.0 - CommonMark with GitHub Flavored Markdown converter
(C) 2014-2016 John MacFarlane

❯ /System/Volumes/Data/usr/local/opt/cmark-gfm/bin/cmark-gfm --to commonmark --width 80 ./dash-separated-link-list.md | /System/Volumes/Data/usr/local/opt/cmark-gfm/bin/cmark-gfm
<ul>
<li><a href="#link-1">Link 1</a> - Description of line 1.</li>
<li><a href="#link-2">Link 2</a> - A very long description for the second link in the list.
That description is more than 80 characters wide.</li>
<li><a href="#link-3">This is a very long title, pointing to an awesome article on incredible
stuff we're not used to see everyday</a> - Line #3's description.</li>
<li><a href="#this-is-a-very-long-url-that-is-pointing-to-a-really-really-great-website">Link number
three</a>
<ul>
<li>Fourth description.</li>
</ul>
</li>
</ul>