jar: Package a.b.c missing from ModulePackages class file attribute

Question

I have two maven versions:

Apache Maven 3.8.5 (3599d3414f046de2324203b78ddcf9b5e4388aa0)
Maven home: /opt/netbeans-14/java/maven
Java version: 21.0.1, vendor: Oracle Corporation, runtime: /opt/jdk-21.0.1

and

Apache Maven 3.9.3 (21122926829f1ead511c958d89bd2f672198ae9f)
Maven home: /opt/netbeans-19/java/maven
Java version: 21.0.1, vendor: Oracle Corporation, runtime: /opt/jdk-21.0.1

When I compile my JPMS module with 3.8.5 (clean install) then it is build without any problems. When I compile the module with 3.9.3 (clean install) I get:

[INFO] --- jar:3.3.0:jar (default-jar) @ mymodule-impl ---
[INFO] Building jar: /home/pavel/mymodule-impl/target/mymodule-impl-1.0.0.jar
jar: Package a.b.c missing from ModulePackages class file attribute
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
Total time:  3.386 s
Finished at: 2023-11-03T20:34:05+02:00
------------------------------------------------------------------------
Failed to execute goal org.apache.maven.plugins:maven-jar-plugin:3.3.0:jar (default-jar) on project mymodule-impl: Error assembling JAR: Could not create modular JAR file. The JDK jar tool exited with 1 -> [Help 1]

Could anyone say why it is not built in the second case? Is this a bug?

Answer 1

I've found out what is the problem. If package a.b.c doesn't have classes inside then maven 3.8.5 compiles, but maven 3.9.3 gives Package a.b.c missing from ModulePackages class file attribute error. I had classes but all they were commented inside, so I couldn't see that the package is empty.