为什么 async 会阻止 twitter 回调触发？

Question

我正在将一些基本节点脚本转换为 Lambda 函数。其中一个脚本使用 twitter SDK 来获取一些推文。这本质上是如何使用基本 AWS Lambda 样板调用 API 的示例。如果你运行它，回调将不会触发，它基本上会跳过 twitter.get 函数。但是，如果您从exports.handler 函数中删除异步，它会触发人们期望的方式。

我以为我理解异步等待，但为什么它会阻止回调被触发？也许 twitter SDK 会感知到它何时是异步函数并返回一个承诺？

const Twitter = require('twitter');

exports.handler = async (event, context, callback) => {
  console.log("The function started") // this line gets logged

const twitter = new Twitter({
  consumer_key: process.env.consumer_key,
  consumer_secret: process.env.consumer_secret,
  access_token_key: process.env.access_token_key,
  access_token_secret: process.env.access_token_secret
});

  const params = {
    screen_name: 'xxxx',
    count: 10,
    tweet_mode: 'extended'
  };
  const twitterEndpoint = 'statuses/user_timeline.json';


twitter.get(twitterEndpoint, params,  function(error, tweets, response) { //this doesn't...
    console.log("TWEETS", tweets, "ERROR", error, "RESPONSE", response) // this line does not log out
    if (!error) {
      console.log(tweets)
    }else{
      console.log(error, "There was an error calling twitter!")
    }
  });
}

Answer 1

跟进我们在 cmets 中的谈话：如果处理程序是异步函数，AWS Lambda 一定希望您返回一个 Promise。

如果您想使用异步处理程序，请尝试承诺 twitter.get() 函数：

exports.handler = async (event, context, callback) => {
  console.log("The function started") // this line gets logged

  const twitter = new Twitter({
    consumer_key: process.env.consumer_key,
    consumer_secret: process.env.consumer_secret,
    access_token_key: process.env.access_token_key,
    access_token_secret: process.env.access_token_secret
  });

  const params = {
    screen_name: 'xxxx',
    count: 10,
    tweet_mode: 'extended'
  };
  const twitterEndpoint = 'statuses/user_timeline.json';

  return new Promise((resolve, reject) => {
    twitter.get(twitterEndpoint, params,  function(error, tweets, response) { //this doesn't...
      console.log("TWEETS", tweets, "ERROR", error, "RESPONSE", response) // this line does not log out
      if (!error) {
        console.log(tweets)
        resolve();
      }else{
        console.log(error, "There was an error calling twitter!")
        reject();
      }
    }); 
  });
}