我有一个节点应用程序，它 生成 一个 child_process 。当 child_process 运行完毕时，我想解决一个承诺。以下代码有效，但 .then() 语句出现顺序错误：

const storage = require('./storage');
const logging = require('./logging');
const process = require('child_process').spawn;


function convertIncomingFile(pathToFile) {
  logging.info(`Converting ${pathToFile}`);
  const convert = process(`cat`, [pathToFile], {});

  return Promise.resolve(
    convert.stdout.on('data', (data) => {
      logging.info(data.toString('utf8'));
    }),
    convert.stderr.on('data', (err) => {
      logging.error(err);
    }),
    convert.on('close', (code) => {
      logging.info(`Conversion finished with status code ${code}`);
    })
  );
}

module.exports = {
  convertFile: (filename) => {
    storage.downloadFile(filename).
      then((localFilename) => {
        logging.info(`File saved to: ${localFilename}`);
      }).
      then(() => convertIncomingFile(`./files/${filename}`)).
      then(() => {
        logging.info(`Coversion of ${filename} complete.`);
      }).
      catch((apiErr) => {
        logging.error(apiErr);
      });
  }
};

我得到的输出是：

info: File saved to: ./files/package.json
info: Converting ./files/package.json
info: Coversion of package.json complete.
info: {
 <file contents>
}

info: Conversion finished with status code 0

如您所见， Conversion of package.json complete. 语句发生在文件内容记录和转换状态代码语句之前。为什么会出现这种情况？我如何让“转换完成”语句出现在“状态代码”语句之后？