I'm trying to generate checkstyle report with maven (mvn checkstyle:checkstyle) and it fails... I'm executing it at the root folder of xwiki source. I use maven 2.0.8, and tried without success with version 2.0.9, and 2.1-SNAPSHOT. Here the trace (see trace.txt attached for full trace) : [ERROR] FATAL ERROR [INFO] ------------------------------------------------------------------------ [INFO] An invalid artifact was detected. This artifact might be in your project's POM, or it might have been included transitively during the resolution process. Here is the information we do have for this artifact: o GroupID: com.xpn.xwiki.platform.tools o ArtifactID: xwiki-verification-resources o Version: <<< MISSING >>> o Type: jar [INFO] ------------------------------------------------------------------------ [INFO] Trace org.apache.maven.artifact.InvalidArtifactRTException: For artifact {com.xpn.xwiki.platform.tools:xwiki-verification-resources:null:jar}: The version cannot be empty. at org.apache.maven.artifact.DefaultArtifact.validateIdentity(DefaultArtifact.java:147) at org.apache.maven.artifact.DefaultArtifact.<init>(DefaultArtifact.java:122) at org.apache.maven.artifact.factory.DefaultArtifactFactory.createArtifact(DefaultArtifactFactory.java:158) at org.apache.maven.artifact.factory.DefaultArtifactFactory.createDependencyArtifact(DefaultArtifactFactory.java:70) at org.apache.maven.project.artifact.MavenMetadataSource.createArtifacts(MavenMetadataSource.java:334) at org.apache.maven.plugin.DefaultPluginManager.addPlugin(DefaultPluginManager.java:343) at org.apache.maven.plugin.DefaultPluginManager.verifyVersionedPlugin(DefaultPluginManager.java:208) at org.apache.maven.plugin.DefaultPluginManager.verifyPlugin(DefaultPluginManager.java:172) at org.apache.maven.lifecycle.DefaultLifecycleExecutor.verifyPlugin(DefaultLifecycleExecutor.java:1257) at org.apache.maven.lifecycle.DefaultLifecycleExecutor.getMojoDescriptor(DefaultLifecycleExecutor.java:1522) at org.apache.maven.lifecycle.DefaultLifecycleExecutor.segmentTaskListByAggregationNeeds(DefaultLifecycleExecutor.java:386) at org.apache.maven.lifecycle.DefaultLifecycleExecutor.execute(DefaultLifecycleExecutor.java:138) at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:333) at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:126) at org.apache.maven.cli.MavenCli.main(MavenCli.java:282) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:585) at org.codehaus.classworlds.Launcher.launchEnhanced(Launcher.java:315) at org.codehaus.classworlds.Launcher.launch(Launcher.java:255) at org.codehaus.classworlds.Launcher.mainWithExitCode(Launcher.java:430) at org.codehaus.classworlds.Launcher.main(Launcher.java:375) -- Julien Lancelot Hortis, Consulting & Innovation team Sonar , Open Source Quality Dashboard for Java projects Try Sonar at http://sonar.hortis.ch