Set<VirtualFile> () { if (ourEternallyLivingFilesCache != null) { return ourEternallyLivingFilesCache; } Set<VirtualFile> survivors = new HashSet<>(); for (IndexableSetContributor contributor : IndexableSetContributor.EP_NAME.getExtensions()) { for (VirtualFile file : IndexableSetContributor.getRootsToIndex(contributor)) { registerSurvivor(survivors, file); } } ourEternallyLivingFilesCache = survivors; return survivors; }