When jdt compiler used (using takari-lifecycle, packaging takari-jar, compilerId jdt), the generated sources are invalid, the package declaration is twice present in source and naturally chokes the compilation.

Edited short snippet from generated code:

...
*/

package package org.cstamas.vertx.orientdb;

import org.cstamas.vertx.orientdb.GraphDatabaseService;
import io.vertx.core.eventbus.DeliveryOptions;
import io.vertx.core.Vertx;
import io.vertx.core.Future;
...

As you see, the line package package org.cstamas.vertx.orientdb; is wrong.

Reason:
As I debugged, it seems that problem lies in ClassModel line 504. The toString() method of JDT implementation org.eclipse.jdt.internal.compiler.apt.model.ElementImpl returns package org.cstamas.vertx.orientdb instead of expected org.cstamas.vertx.orientdb.

So, to make it work on javac but also on jdt compiler, it might be useful to add some check and remove the package prefix if present. Manually verified, that IF one of the two package keywords are removed, the generated code is just fine.

Reproducer: repo at this hash, used mvnDebug w/ remote debugger
https://github.com/cstamas/vertx-orientdb/tree/6062a5b1544a7e1711f3f82a68585085f8742f0a