Then, I realized it happened on two different instances of Eclipse and for the writing of Develop Vaadin apps with Scala, I used 3 different libraries, so I wanted to correct the problem. At first, I blamed it on the JRebel plugin I recently installed, then I began investigating the case further and I found out that I needed a special Maven connector that was present in neither of my Eclipse instances: the WTP connector. I had installed this kind of connector back when Maven Integration was done by m2eclipse by Sonatype, but had forgotten that a while ago. Now the integration is called m2e, but I have to do the whole nine yards again…
The diagnostics that can be hard but the solution is very simple.
Go to the Windows -> Preferences menu and from this point on go to Maven -> Discovery.
Click on Open Catalog.
Search for “wtp”, select Maven Integration for WTP and click on Finish. Restart and be pleased. Notice that most Maven plugins integration in Eclipse can be resolved the same way.
For a sum up on my thoughts about the current state of m2e, please see here.