code: public File getCompiled(AssetInfo asset, File starter) throws IOException, ServiceException {
          File file;
          synchronized(WebpackCache.class) {
              file = webpackAssets.get(asset);
              if (file == null || !file.exists() || file.lastModified() < asset.getFile().lastModified()
                      || (starter != null && file.lastModified() < starter.lastModified())) {
                  file = getOutput(asset);
                  compile(asset, starter, file);
                  return file;
              }
          }
          return file;
      }
docs: Starter file will be compiled, but asset used to compute output path.