Please keep in mind that my application is a pretty large one and every small incompatibility with the old versions create a huge amount of work when upgrading.
Trying to upgrade from JSF 1.2 + Facelets to JSF 2, I've noticed this incompatibility:
javax.faces.view.facelets.TagException: /layout/template.xhtml @63,39 <c:set> var set with null or empty value
Searching on Google, I saw that there are some more reports with this issue, but no clear answer on the reason of this change.
From reading this I got the impression that this should be a valid statement and it should lead to that attribute being removed.
This is the (very reduced) case that I'm trying to solve: