private static void addSourceDirectoriesFromLibraries( @NotNull Project project, @NotNull VirtualFile directory, @NotNull Collection<VirtualFile> outSourceRoots) { ProjectFileIndex index = ProjectFileIndex.SERVICE.getInstance(project); VirtualFile classRoot = index.getClassRootForFile(directory); if (classRoot == null) return; String relativePath = VfsUtilCore.getRelativePath(directory, classRoot); if (relativePath == null) return; for (OrderEntry orderEntry : index.getOrderEntriesForFile(directory)) { for (VirtualFile sourceRoot : orderEntry.getFiles(OrderRootType.SOURCES)) { VirtualFile sourceFile = sourceRoot.findFileByRelativePath(relativePath); if (sourceFile != null) { outSourceRoots.add(sourceFile); } } } }