List<FileRef> files = Lists.newArrayList();
files.addAll(gxpFiles);
files.addAll(extraFiles());
// compile
CompilationSet compilationSet = getCompilationSetBuilder().build(files);
AlertSink alertSink = createAlertSink();
compilationSet.compile(alertSink, getAlertPolicy(), getOutputLanguages(),
getAllowedOutputPredicate(gxpFiles));
return compilationSet;
}