Eclipse Google Plugin - WTP Server - Not creating lib folder

since a few days the Eclipse plugins started to show this error.

The project is an App Engine project based on Maven, and the dev-server is launched using the WTP integration provided by the Google Eclipse Plugin.

AVVERTENZA: failed com.google.appengine.tools.development.DevAppEngineWebAppContext@345541bd{/,C:\Noovle\workspace.metadata.plugins\org.eclipse.wst.server.core\tmp0\Ape_Core}: java.lang.NoClassDefFoundError: com/google/appengine/api/utils/SystemProperty

Here is the full stack trace when the server is loaded

lug 07, 2015 11:43:12 AM java.util.prefs.WindowsPreferences <init>
AVVERTENZA: Could not open/create prefs root node Software\JavaSoft\Prefs at root 0x80000002. Windows RegCreateKeyEx(...) returned error code 5.
lug 07, 2015 11:43:12 AM com.google.apphosting.utils.config.AppEngineWebXmlReader readAppEngineWebXml
INFORMAZIONI: Successfully processed C:\Noovle\workspace\.metadata\.plugins\org.eclipse.wst.server.core\tmp0\Ape_Core\WEB-INF/appengine-web.xml
lug 07, 2015 11:43:12 AM com.google.apphosting.utils.config.AbstractConfigXmlReader readConfigXml
INFORMAZIONI: Successfully processed C:\Noovle\workspace\.metadata\.plugins\org.eclipse.wst.server.core\tmp0\Ape_Core\WEB-INF/web.xml
lug 07, 2015 11:43:13 AM com.google.appengine.tools.development.SystemPropertiesManager setSystemProperties
INFORMAZIONI: Overwriting system property key 'java.util.logging.config.file', value 'C:\Users\Nicola\.m2\repository\com\google\appengine\appengine-java-sdk\1.9.22\appengine-java-sdk\appengine-java-sdk-1.9.22\config\sdk\logging.properties' with value 'WEB-INF/logging.properties' from 'C:\Noovle\workspace\.metadata\.plugins\org.eclipse.wst.server.core\tmp0\Ape_Core\WEB-INF\appengine-web.xml'
lug 07, 2015 11:43:13 AM com.google.apphosting.utils.jetty.JettyLogger info
INFORMAZIONI: Logging to JettyLogger(null) via com.google.apphosting.utils.jetty.JettyLogger
lug 07, 2015 11:43:14 AM com.google.apphosting.utils.jetty.JettyLogger info
INFORMAZIONI: jetty-6.1.x
lug 07, 2015 11:43:18 AM com.google.apphosting.utils.jetty.JettyLogger warn
AVVERTENZA: failed com.google.appengine.tools.development.DevAppEngineWebAppContext@345541bd{/,C:\Noovle\workspace\.metadata\.plugins\org.eclipse.wst.server.core\tmp0\Ape_Core}: java.lang.NoClassDefFoundError: com/google/appengine/api/utils/SystemProperty
lug 07, 2015 11:43:18 AM com.google.apphosting.utils.jetty.JettyLogger warn
AVVERTENZA: failed JettyContainerService$ApiProxyHandler@2b8d9248: java.lang.NoClassDefFoundError: com/google/appengine/api/utils/SystemProperty
lug 07, 2015 11:43:18 AM com.google.apphosting.utils.jetty.JettyLogger warn
AVVERTENZA: Error starting handlers
java.lang.NoClassDefFoundError: com/google/appengine/api/utils/SystemProperty
    at it.noovle.ape.tools.ToolsEnvironment.getApplicationVersion(ToolsEnvironment.java:26)

After some analysis I found the problem: when the server is published (or even a new one is created) the lib folder in WEB-INF is not created.

I'm sure about that because if I copy the lib folder from another project (they share the same libraries) the server starts without problems.

I tried a clean start creating a new server, and as expected the lib folder is missing.

In the Error Log tab of Eclipse no problems are shown during the creation and publication of the server

I also need to clarify that if I launch the project with the devserver maven goal, there are no problems at all.

I'm running on Windows 8 with Eclipse Mars (my coworker has Luna instead but same problem is shown). The version of Google Plugin is Google Plugin for Eclipse 4.4 3.8.0.v201410302155-rel-r44. Another coworker of mine has the same version of the plugin with Eclipse Luna and does not show this problem

Is there a way to debug the steps of the WTP plugin to understand why the lib folder is not created? Which is the possible explanation of this behaviour?

Solved, missing Maven Dependencies on Deployment Assembly project properties