@NotNull private Set<JetFile> getBuiltInSourceFiles(@NotNull URL url) { String fromUrl = VfsUtilCore.convertFromUrl(url); VirtualFile vf = VirtualFileManager.getInstance().findFileByUrl(fromUrl); assert vf != null : "Virtual file not found by URL: " + url; // Refreshing VFS: in case the plugin jar was updated, the caches may hold the old value vf.getChildren(); vf.refresh(false, true); PathUtil.getLocalFile(vf).refresh(false, true); PsiDirectory psiDirectory = PsiManager.getInstance(myProject).findDirectory(vf); assert psiDirectory != null : "No PsiDirectory for " + vf; return new HashSet<JetFile>( ContainerUtil.mapNotNull( psiDirectory.getFiles(), new Function<PsiFile, JetFile>() { @Override public JetFile fun(PsiFile file) { return file instanceof JetFile ? (JetFile) file : null; } })); }