[4.x]: Markdown extra incorrect Special Attributes behaviour

[pixelmachine]

What happened?

I have a plain text field which uses Markdown Extra e.g. {{ copy | markdown('extra', false) }} which works fine except Markdown Extra's "Special Attributes" fail for certain formatting.

This works:
[Google](http://www.google.com){attr=value}
Output:
<p><a href="http://www.google.com" attr="value">Google</a></p>

As do classes and IDs like this {.class #id}.

This does NOT work:
[Google](http://www.google.com){target=_blank}
Output:
<p><a href="http://www.google.com">Google</a>{target=_blank}</p>

Expected behavior

According to the Dingus on the Markdown Extra site, this formatting should be valid.

Dingus output:
<p><a href="http://www.google.com" target="_blank">Google</a></p>

Presumably the _ is causing the failure.

Craft CMS version

Craft CMS 4.3.6.1

PHP version

8.1.17

[brandonkelly]

That should be reported over at https://github.com/cebe/markdown (the library that’s currently used for Markdown parsing in Craft). However it’s mostly abandoned, so we’re planning to switch to league/commonmark in Craft 5.

[pixelmachine]

@brandonkelly as I said the formatting does work using PHP Markdown Extra and that can be tested via the link. It only doesn't work in Craft's implementation.

Commonmark doesn't support this syntax sadly.

[pixelmachine]

Ah wait, I see what you're saying, I didn't spot that was a multi-markdown library. It's libraries all the way down. I assumed you were just using PHP Markdown Extra.

I can confirm that it doesn't work using cebe/markdown and in fact they say that Markdown Extra is not fully supported. Perhaps worth mentioning in the docs?

[brandonkelly]

@pixelmachine Ah good catch.