code: protected void extendProjectCompileRootsAndResources() throws MojoExecutionException {
  		if (project != null) {
  			try {
  				extendCompileSourceRoots();
  				extendResources(outletResDir, false);
  				extendResources(outletResOnceDir, false);
  				extendResources(outletResTestDir, true);
  				extendResources(outletResTestOnceDir, true);
  			} catch (Exception ex) {
  				throw new MojoExecutionException("Could not extend the " + "projects compile paths", ex);
  			}
  		}
  	}
docs: Extends {@link MavenProject}s compile source roots and resource
  directories with the directories holding the generated artifacts.
  <p>
  There's no problem to call this method multiple time. The corresponding
  directories are added only once.