doxia-module-markdown is a Maven plugin that enables Markdown in Maven documentations. In version 1.8, the developers have moved from Pegdown to Flexmark as Markdown parser. It's a good choice, as Flexmark is considerable faster and is still being maintained, while Pegdown officially reached its end of life in 2016.
However, with that switch, code blocks are not syntax highlighted any more. The reason is that the maven-fluido-skin uses code-prettify for syntax highlighting. It runs browser-side, highlighting all <pre> and <code> blocks selecting the prettyprint CSS class. This was true with Pegdown, but Flexmark selects a source class instead.
An obvious workaround is to use a small JavaScript snippet that adds a prettyprint class to all blocks selecting a source class, and then running prettyPrint() again. To do so, this block needs to be added to the <head> section of site.xml:
<head>
<!-- Workaround for https://issues.apache.org/jira/browse/DOXIA-571 -->
<![CDATA[<script type="text/javascript">
$(document).ready(function () {
$(".source").addClass("prettyprint");
prettyPrint();
});
</script>]]>
</head>
It's hard to tell if this is a bug in doxia-module-markdown or in maven-fluido-skin. Also see my bug report at Apache's JIRA.
This was a Google Plus comment that I have now moved to my blog as Google Plus is going to be closed. Thanks to Clement Escoffier for the inspiration.