将回调转换为异步会引发错误

Question

以下代码有效：

  var smtpConfig = {
    host: 'localhost',
    port: 465,
    secure: true, // use SSL
    selfSigned: true
  };

  // create reusable transporter object using the default SMTP transport
  var transporter = nodemailer.createTransport(smtpConfig);

  // setup e-mail data with unicode symbols
  var mailOptions = {
    from: '"Some One" <someone@example.com>', // sender address
    to: 'validuser@company.com', // list of receivers
    subject: 'Hello', // Subject line
    text: 'Hello world ?', // plaintext body
    html: '<b>Hello world ?</b>' // html body
  };

  transporter.sendMail(mailOptions, (error, info) => {
      if (error) {
          console.log(error);
      } else {
          console.log(info);
      }
  });

但是，如果我使用来自节点

的 util.promisify

  var sendMail = promisify(transporter.sendMail);
  var info = await sendMail(mailOptions);

我遇到异常

TypeError: Cannot read property 'getSocket' of undefined
  at sendMail (c:\Users\user\Source\project\node_modules\nodemailer\lib\mailer\index.js:143:25)
  at sendMail (internal/util.js:230:26)

问题出在 sendMail 内部，因为 'this' 未定义：

/**
 * Sends an email using the preselected transport object
 *
 * @param {Object} data E-data description
 * @param {Function?} callback Callback to run once the sending succeeded or failed
 */
sendMail(data, callback) {
    let promise;

    if (!callback && typeof Promise === 'function') {
        promise = new Promise((resolve, reject) => {
            callback = shared.callbackPromise(resolve, reject);
        });
    }

    if (typeof this.getSocket === 'function') { <-- this is undefined
        this.transporter.getSocket = this.getSocket;
        this.getSocket = false;
    }

在普通函数上使用 util.promisify 是可行的。我想这是因为我在 class 方法上使用了 util.promisify。

有没有办法实现这个，或者我需要用 async function sendMail 重载

扩展扩展 class

Answer 1

要解决这个特殊情况，您可以使用

await sendMail.call(transporter, mailOptions) // provide a context

当然，查看 transporter.sendMail() 的源代码，它已经支持作为 thenable 调用而无需包装在 util.promisify() 中，因此您可以直接 await :

await transporter.sendMail(mailOptions) // omit callback to kick in promise-style async

将回调转换为异步会引发错误

converting callback to async throws error

node.js

async-await

typescript

nodemailer

es6-promise