TypeScript + Express: Property 'rawBody' does not exist on type 'IncomingMessage'

Question

In my src/app.ts, I have:

import express from 'express';
import bodyParser from 'body-parser';
const app = express()

app.use(bodyParser.json({ verify: (req, res, buf) => req.rawBody = buf }))

But I get the error Property 'rawBody' does not exist on type 'IncomingMessage' on:

app.use(bodyParser.json({ verify: (req, res, buf) => req.rawBody = buf }))

I have a typings/express.d.ts, in which I have:

declare namespace Express {
    export interface Request {
        rawBody: any;
    }
}

and my tsconfig.json is:

{
    "compilerOptions": {
        "outDir": "./built",
        "allowJs": true,
        "target": "es6",
        "esModuleInterop": true,
        "sourceMap": true,
        "moduleResolution": "node"
    },
    "include": [
        "./src/**/*"
    ],
    "files": [
        "typings/*"
    ]
}

So what am I doing wrong?

Answer 1

There are two issues here:

1. tsconfig.json

The files option in tsconfig.json doesn't support wildcards like typings/*, only explicit filenames.

You can either specify the full path:

"files": [
    "typings/express.d.ts"
]

Or add the wildcard path to include:

"include": [
    "./src/**/*",
    "typings/*"
]

2. Wrong Type

The error message mentions the type IncomingMessage, however you are augmenting the Request interface instead. Take a look at the type definitions for body-parser (parts omitted):

import * as http from 'http';

// ...

interface Options {
    inflate?: boolean;
    limit?: number | string;
    type?: string | string[] | ((req: http.IncomingMessage) => any);
    verify?(req: http.IncomingMessage, res: http.ServerResponse, buf: Buffer, encoding: string): void;
}

The first argument of verify has the type http.IncomingMessage from the 'http' module that's included with Node.js.

To augment the correct type, you'll want to change your .d.ts file to this:

declare module 'http' {
    interface IncomingMessage {
        rawBody: any;
    }
}