[Rd] How to avoid the Markdown code block bug on R Bugzilla

[Ivan Krylov]

Hello,

There's a rare but annoying bug in Bugzilla 5.1.2...5.3.2+ where a
Markdown code block inside a comment may be replaced by U+F111 or
U+F222, and then the following code blocks may end up being replaced by
the preceding ones. For example, the problem can be seen in PR16158:
https://bugs.r-project.org/show_bug.cgi?id=16158.

Here's how to avoid it:

1. If no code blocks have been already swallowed by Bugzilla, use the
comment preview to make sure yours won't be swallowed either. If you do
see a  or a  instead of your code block in the preview tab, try:
 - starting the comment with an empty line
 - removing the colons from the starting sentence
 - if all else fails, switching Markdown off

2. If you would like to post some code into a bug where this has
already happened, the preview won't be enough. Bugzilla::Markdown has
separate queues for fenced code blocks and indented code blocks, so if
one was swallowed, it may be possible to post the other. Unfortunately,
you won't know whether it'll fail until you post the comment, and by
then it may be a part of the problem. The only safe way to continue is
to switch Markdown off for the comment.

A technical analysis of the bug is available at
<https://lists.bugzilla.org/pipermail/support-list/2024-February/000238.html>,
but it may take a while to get this fixed on the Bugzilla side.

-- 
Best regards,
Ivan