code: function hookGenerator(transformer, sourceNode, source, meta) {
    if (
      // filter missing nodes
      !sourceNode ||
      // filter nodes without children
      (sourceNode.nodes && !sourceNode.nodes.length) ||
      // filter empty javascript and css nodes
      (!sourceNode.nodes && !sourceNode.text)) {
      return result => result
    }
  
    return curry(transformer)(sourceNode, source, meta)
  }
docs: Prepare the riot parser node transformers
  @param   { Function } transformer - transformer function
  @param   { Object } sourceNode - riot parser node
  @param   { string } source - component source code
  @param   { Object } meta - compilation meta information
  @returns { Promise<Output> } object containing output code and source map