Express：无法设置只有 getter 的 #<IncomingMessage> 的属性 ip

Question

我正在尝试创建一个中间件，将用户的 IP 设置为它为我们提供的 cloudflare 标头，用于应用程序的其余部分。这曾经适用于我的项目，但现在由于某种原因，它不起作用。

当我尝试导航到应用程序时，出现以下错误：

TypeError: Cannot set property ip of #<IncomingMessage> which has only a getter
    at /media/chen/storage/development/urlshortener/index.ts:67:11
    at Layer.handle [as handle_request] (/media/chen/storage/development/urlshortener/node_modules/express/lib/router/layer.js:95:5)
    at trim_prefix (/media/chen/storage/development/urlshortener/node_modules/express/lib/router/index.js:317:13)
    at /media/chen/storage/development/urlshortener/node_modules/express/lib/router/index.js:284:7
    at Function.process_params (/media/chen/storage/development/urlshortener/node_modules/express/lib/router/index.js:335:12)
    at next (/media/chen/storage/development/urlshortener/node_modules/express/lib/router/index.js:275:10)
    at jsonParser (/media/chen/storage/development/urlshortener/node_modules/body-parser/lib/types/json.js:110:7)
    at Layer.handle [as handle_request] (/media/chen/storage/development/urlshortener/node_modules/express/lib/router/layer.js:95:5)
    at trim_prefix (/media/chen/storage/development/urlshortener/node_modules/express/lib/router/index.js:317:13)
    at /media/chen/storage/development/urlshortener/node_modules/express/lib/router/index.js:284:7

app.use((req, res, next) => {
  req.ip = req.header('cf-connecting-ip') || req.ip; // Line 67, which the error is mentioning
  next()
})

如果我应该包含我的其余代码，请告诉我。这就是除了app.listen 之外的所有路由、中间件和快速设置都包含在其中的承诺

我使用的是 Express 4.17.1

Answer 1

您正在尝试设置请求属性为defined as getter。

在严格模式下运行时会引发错误。

证明：

(function() {
  'use strict';
  
  let obj = {};

  Object.defineProperty(obj, 'myProp', {
    configurable: true,
    enumerable: true,
    get: () => { return 'from getter' }
  });

  // with 'strict mode': Uncaught TypeError: Cannot set property myProp of #<Object> which has only a getter
  // without 'strict mode': executed silently and has no effect on the `myProp`.
  obj.myProp = 'explicitly set';

  // with 'strict mode': never reached
  // without 'strict mode': prints 'from getter'
  console.log(obj.myProp);
}());

您可以在请求对象上引入新属性，例如req.endUserIp 稍后在您的代码中使用它。

由于您使用 TypeScript 标记了问题，因此您可能还想使用新属性 extend the Request interface。