Required class missing: BaseLanguageModule (with maven plugin)

[pzygielo]

Here's what I get, when trying 7.0.0-rc2 with the current maven-pmd-plugin:

A required class was missing while executing org.apache.maven.plugins:maven-pmd-plugin:3.20.0:pmd: net/sourceforge/pmd/lang/BaseLanguageModule
...
Caused by: java.lang.ClassNotFoundException: net.sourceforge.pmd.lang.BaseLanguageModule
    at org.codehaus.plexus.classworlds.strategy.SelfFirstStrategy.loadClass (SelfFirstStrategy.java:50)
    at org.codehaus.plexus.classworlds.realm.ClassRealm.unsynchronizedLoadClass (ClassRealm.java:271)
    at org.codehaus.plexus.classworlds.realm.ClassRealm.loadClass (ClassRealm.java:247)
    at org.codehaus.plexus.classworlds.realm.ClassRealm.loadClass (ClassRealm.java:239)
    at java.lang.ClassLoader.defineClass1 (Native Method)
    at java.lang.ClassLoader.defineClass (ClassLoader.java:1012)
    at java.security.SecureClassLoader.defineClass (SecureClassLoader.java:150)
    at java.net.URLClassLoader.defineClass (URLClassLoader.java:524)
    at java.net.URLClassLoader$1.run (URLClassLoader.java:427)
    at java.net.URLClassLoader$1.run (URLClassLoader.java:421)
    at java.security.AccessController.doPrivileged (AccessController.java:712)
    at java.net.URLClassLoader.findClass (URLClassLoader.java:420)
    at org.codehaus.plexus.classworlds.realm.ClassRealm.loadClassFromSelf (ClassRealm.java:425)
    at org.codehaus.plexus.classworlds.strategy.SelfFirstStrategy.loadClass (SelfFirstStrategy.java:42)
    at org.codehaus.plexus.classworlds.realm.ClassRealm.unsynchronizedLoadClass (ClassRealm.java:271)
    at org.codehaus.plexus.classworlds.realm.ClassRealm.loadClass (ClassRealm.java:247)
    at org.codehaus.plexus.classworlds.realm.ClassRealm.loadClass (ClassRealm.java:239)
    at java.lang.Class.forName0 (Native Method)
    at java.lang.Class.forName (Class.java:467)
    at java.util.ServiceLoader$LazyClassPathLookupIterator.nextProviderClass (ServiceLoader.java:1217)
    at java.util.ServiceLoader$LazyClassPathLookupIterator.hasNextService (ServiceLoader.java:1228)
    at java.util.ServiceLoader$LazyClassPathLookupIterator.hasNext (ServiceLoader.java:1273)
    at java.util.ServiceLoader$2.hasNext (ServiceLoader.java:1309)
    at java.util.ServiceLoader$3.hasNext (ServiceLoader.java:1393)
    at net.sourceforge.pmd.lang.LanguageRegistry.loadLanguages (LanguageRegistry.java:119)
    at net.sourceforge.pmd.lang.LanguageRegistry.<clinit> (LanguageRegistry.java:43)
    at net.sourceforge.pmd.PMDConfiguration.<clinit> (PMDConfiguration.java:105)
    at org.apache.maven.plugins.pmd.exec.PmdExecutor.run (PmdExecutor.java:181)
    at org.apache.maven.plugins.pmd.exec.PmdExecutor.execute (PmdExecutor.java:83)
    at org.apache.maven.plugins.pmd.PmdReport.executePmd (PmdReport.java:390)
    at org.apache.maven.plugins.pmd.PmdReport.canGenerateReport (PmdReport.java:315)

Not sure if this is caused by

• my configuration (would it be possible to see what is missing/wrong there rather than that exception?),
• plugin (I can't see any report about that at https://issues.apache.org/jira/projects/MPMD/issues/MPMD-370?filter=allissues),
• PMD itself.

Extracted example: https://github.com/pzrep/pmd-700rcX/actions/runs/4870777385/jobs/8686943805?pr=1

[adangel]

See #4478 for a snapshot version of the maven-pmd-plugin.

As PMD 7 is a major release, it is not compatible with PMD 6 - which maven-pmd-plugin is built against.