code: @Override
      public String getExtraJvmArgs()
      {
          String extras = super.getExtraJvmArgs();
          extras += " -Xdebug -Xnoagent -Djava.compiler=NONE -Xrunjdwp:transport=dt_socket";
          extras += ",server=" + ( attachDebugger ? "n" : "y" );
          extras += ",address=" + debugPort;
          extras += ",suspend=" + ( debugSuspend ? "y" : "n" );
          return extras;
      }
docs: Override extraJVMArgs to append JVM debugger option
  <p>
  {@inheritDoc}
  
  @see org.codehaus.mojo.gwt.shell.AbstractGwtShellMojo#getExtraJvmArgs()