code: function tryPathsLookUp(info, file, opts) {
    var id = info.rest;
    var test;
  
    if (/^([^\/]+)(?:\/(.*))?$/.test(id)) {
      var parts = id.split('/');
      var idx = parts.length;
  
      while (idx > 0) {
        var prefix = parts.slice(0, idx).join('/');
        var subpath = parts.slice(idx).join('/');
  
        var dirs;
        if ((dirs = paths[prefix])) {
          for (var i = 0, len = dirs.length;
            (!test || !test.file) && i < len; i++) {
            test = subpath ? findResource(subpath, path.join(baseUrl, dirs[i]), opts.extList) : findResource(dirs[i], baseUrl, opts.extList);
          }
        }
        idx--;
      }
    }
  
    return test;
  }
docs: 在 Paths 中查找