为什么 netlify-lambda 在 Promise 上使用 async/await 时会记录 UnhandledPromiseRejectionWarning？

Question

我正在尝试为此创建一个 lambda function on Netlify and I'm using their Netlify Lambda CLI。

现在，我在 Promise 上使用 async/await 时遇到问题，因为它会记录 UnhandledPromiseRejectionWarning，即使我正在使用 try/catch。

这是一个演示：

import fetch from "node-fetch";

exports.handler = async function(event, context, callback) {
    try {
        const response = await fetch("https://api.chucknorris.io/jokes/random");
        const data = await response.json();

        callback(null, {
            statusCode: 200,
            body: data.value
        });
    } catch (err) {
        console.error(err);
    }
};

日志：

netlify-lambda: Starting server
Lambda server is listening on 9000
Hash: 533f41e1d4248894ae20
Version: webpack 4.26.1
Time: 966ms
Built at: 11/28/2018 10:59:44 PM
  Asset      Size  Chunks             Chunk Names
test.js  18.3 KiB       0  [emitted]  test
Entrypoint test = test.js
[0] external "stream" 42 bytes {0} [built]
[1] external "zlib" 42 bytes {0} [built]
[2] external "url" 42 bytes {0} [built]
[3] external "http" 42 bytes {0} [built]
[4] external "https" 42 bytes {0} [built]
[5] ./test.js + 1 modules 40.8 KiB {0} [built]
    | ./test.js 1.14 KiB [built]
    | ../node_modules/node-fetch/lib/index.mjs 39.6 KiB [built]
Request from ::1: GET /test
Response with status 200 in 685 ms.
(node:99167) UnhandledPromiseRejectionWarning: TypeError: Cannot read property 'statusCode' of undefined
    at callback (/Users/nunoarruda/Desktop/test/node_modules/netlify-lambda/lib/serve.js:22:42)
    at /Users/nunoarruda/Desktop/test/node_modules/netlify-lambda/lib/serve.js:41:21
    at process.internalTickCallback (internal/process/next_tick.js:77:7)
(node:99167) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 1)
(node:99167) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

相关 GitHub 问题：https://github.com/netlify/netlify-lambda/issues/43

为什么 netlify-lambda 在对 Promises 使用 async/await 时会记录 UnhandledPromiseRejectionWarning？我该如何解决这个问题？

Answer 1

With the new Node.js 8.10 runtime, there are new handler types that can be declared with the “async” keyword or can return a promise directly.

在 AWS 文档中，v8.10 支持 async/await，Netlify 的新默认设置现在使用此版本。 In the AWS docs，这些示例显示了这两个新的处理程序类型，它们删除了回调的使用。我们应该使用 Netlify 在我们的函数中做同样的事情。

我能够在不使用回调的情况下使用以下代码在本地删除错误消息：

import fetch from "node-fetch";

exports.handler = async function(event, context) {
    try {
        const response = await fetch("https://api.chucknorris.io/jokes/random");
        if (!response.ok) { // NOT res.status >= 200 && res.status < 300
            return { statusCode: response.status, body: response.statusText };
        }
        const data = await response.json();

        return {
            statusCode: 200,
            body: data.value
            // if you want to return whole json string
            // headers: { 'Content-Type': 'application/json' },
            // body: JSON.stringify(data)
        };
    } catch (err) {
        console.log(err); // output to netlify function log
        return {
            statusCode: 500,
            body: err.message // Could be a custom message or object i.e. JSON.stringify(err)
        };
    }
};

为什么 netlify-lambda 在 Promise 上使用 async/await 时会记录 UnhandledPromiseRejectionWarning？

Why netlify-lambda logs an UnhandledPromiseRejectionWarning when using async/await on Promises?

node.js

async-await

aws-lambda

es6-promise

netlify