Hey Kristin,
Thanks a lot for your feedback. Indeed, org.slf4j.ext.XLogger is currently not supported by latest implementation of rule
squid:S2629 (SonarJava 4.14.0.11784).
It's consequently a False Negative, and the analyzer should definitely catch such case as well.
I created the following ticket to improve the rule, and eventually handle it correctly:
SONARJAVA-2534
So, to answer your question, no needs to write a custom rule, we are going to improve it to make it support XLogger when handling the ticket.
As a side note, when reporting such kind of issues (false positive, false negative, rule making analysis crash), it's usually more important to provide the related programming language, and more particularly the version of the analyzer used during analysis! But I admit that in this case, it was obvious! :)
Cheers,
Michael