Markdown: MARKDOWN_HASH appearing in output

[rmccue]

👋 There appears to be a bug with code blocks inside shortcodes. single_line_code_preserve is called first, replacing code tags with their hash markers. shortcode_preserve is then called, replacing shortcodes with their hash markers. After the Markdown parsing, hashes are then removed.

However, since the code tags were removed first, they're first in the array and are restored first. The shortcodes are then restored afterwards. This means that the code tags are never restored.

The simplest solution here is simply to reverse the hash array before restoration. Happy to PR if that seems sensible.

(Hitting this on WordPress.org while working on meta2968.)

Steps to reproduce the issue

Register a test shortcode. The callback doesn't matter (it just needs to be registered so it gets added to the regex).

add_shortcode( 'test', '__return_empty_string' );

Create a post with the following content:

[test]Text with <code>code</code> in it.[/test]

What I expected

Output of:

[test]Text with <code>code</code> in it.[/test]

What happened instead

Output of:

[test]Text with <code>MARKDOWN_HASHc13367945d5d4c91047b3b50234aa7abMARKDOWN_HASH</code> in it.[/test]