Shall CommonMark inline inside HTML5 render as CommonMark? If not, why not?

Spec
1

At github.com/MALSync/MALSync/issues/2092:

…via the available “GitHub-Flavoured Markdown” markup syntax, I am able to utilise CommonMark inside a <code> tag, directly inline:

1.	<code>[por](https://www.loc.gov/standards/iso639-2/php/langcodes_name.php?iso_639_1=pt)[-](https://stackoverflow.com/questions/13630355/culture-name-using-underscore-instead-of-dash#comment18695296_13630355)[BRA](https://en.wikipedia.org/wiki/ISO_3166-1_alpha-3#:~:text=Plurinational%20State%20of%29-,bra,-Brazil)</code>;

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	[1]: https://stackoverflow.com/revisions/40076454/2#:~:text=Sometimes%20you%20need%20to%20encode,%5BSyntax%5D(http://en.wikipedia.org/wiki/Syntax_(programming_languages%2529)

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1.	<code>[por](https://www.loc.gov/standards/iso639-2/php/langcodes_name.php?code_ID=363)[-](https://stackoverflow.com/questions/13630355/culture-name-using-underscore-instead-of-dash#comment18695296_13630355)[EEE](https://en.wikipedia.org/wiki/ISO_3166-1_alpha-3#:~:text=ABB%20Asia-,eee,-Europe)</code>;

1.	[`ro`](https://www.loc.gov/standards/iso639-2/php/langcodes_name.php?iso_639_1=ro);

1.	[`sv`](https://www.loc.gov/standards/iso639-2/php/langcodes_name.php?iso_639_1=sv);

1.	<code>[zho](https://www.loc.gov/standards/iso639-2/php/langcodes_name.php?code_ID=)[-](https://stackoverflow.com/questions/13630355/culture-name-using-underscore-instead-of-dash#comment18695296_13630355)[HANS](https://stackoverflow.com/a/4894634/9731176)</code>; and

1.	<code>[zho](https://www.loc.gov/standards/iso639-2/php/langcodes_name.php?code_ID=)[-](https://stackoverflow.com/questions/13630355/culture-name-using-underscore-instead-of-dash#comment18695296_13630355)[HANT](https://stackoverflow.com/a/4894634/9731176)</code>.

I was under the impression that CommonMark requires a newline between the start and end tags of any HTML5 for the CommonMark within to render, which I still believe to be correct. Please correct me if I’m not. However, with that premise, if this is technically feasible, why is it disallowed by the standard?

2

This is an exceptionally late reply from me, but I happened to see this while reading another post and it’s a question that comes up a lot.

The short answer is, it depends: see § 6.6 Raw HTML for how raw HTML is interpreted inline; note especially the definition of an HTML tag:

An HTML tag consists of an open tag, a closing tag, an HTML comment, a processing instruction, a declaration, or a CDATA section.

In other words, when it comes to inline HTML, there’s no such thing as “inside” a <code> tag: the <code> is itself considered an HTML tag, then there’s some Markdown which is parsed as usual, and then </code> is also considered one. So in this sense, Markdown “within” what we read as a <code>…</code> pair is totally fine, because parsers just treat each in isolation as inline HTML.

You can see this in action by looking at the AST for e.g. the following input:

1. <code>Hello</code> world.

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE document SYSTEM "CommonMark.dtd">
<document xmlns="http://commonmark.org/xml/1.0">
  <list type="ordered" start="1" tight="true" delimiter="period">
    <item>
      <paragraph>
        <html_inline>&lt;code&gt;</html_inline>
        <text>Hello</text>
        <html_inline>&lt;/code&gt;</html_inline>
        <text> world.</text>
      </paragraph>
    </item>
  </list>
</document>

Note each tag is simply html_inline.

Things get more complicated when we consider block HTML, per § 4.6 HTML blocks. The 7 start conditions outline in which cases a compliant parser will suspend treating input as Markdown, and when they’ll resume.

Of particular relevance is start condition 6, as it outlines the majority of tags considered to be “block”: a line that starts with e.g. <table> will suspend parsing until it reaches a blank line. Thus:

<table>
<tr><td>**This won't be emphasised.**</td></tr>
</table>

**This will**

<table><tr><td>

**This will be in a table, *and* will be emphasised.**

</td></tr></table>

Note that <code> is not part of any start condition, so it is interpreted per inline rules even if it happens to come at the start of a line.

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