[SOLVED] How can I extend a flow type for express$Request?

How can I extend a flow type for express$Request?

I am using flow-typed, so it has an express definition. In my code, I have:

isPayloadSignatureValid(req /*: express$Request */ ) {
  const rawBodyPayload = Buffer.from(req.rawBody).toString('utf8')

But flow complains, saying:

Cannot get req.rawBody because property rawBody is missing in express$Request [1].

In my interfaces/express.js, I have:

// @flow
/*::
type express$Request = exports.Request & {
  rawBody: string
}
export type { express$Request };
*/

And in my .flowconfig, I have:


[include]
./interfaces/.*

SO why isn't the extended express$Request having the rawBody property?

Thanks

Solution

You're not gonna get the type from interfaces/express.js when you actually use express. You'd need to import it and inject it yourself. Generally in this situation you'd want to just modify the express libdef from flow-typed directly. Also you should avoid using an intersection type here, you should spread the object types (...).