[Typescript] Argument of type '(req: Request, res: Response<any>) => Promise<Response<any>>' is not assignable to parameter of type...

I’m updating my npm packages from an old version to the latest one. There are a lot of breaking changes but one that I can’t figure out is the following:

I used to have this kind of cloud functions

export const updateLot = functions.https.onRequest(async (req, res) => {
... some code ...

    return res.status(404).json({ message: 'there was an error' })

... some code ...

    return res.status(200).json({ results: my_object })
}

It was compiling fine. Then with the update I get the following error:

Argument of type '(req: Request, res: Response<any>) => Promise<Response<any>>' is not assignable to parameter of type '(req: Request, resp: Response<any>) => void | Promise<void>'.
  Type 'Promise<Response<any>>' is not assignable to type 'void | Promise<void>'.
    Type 'Promise<Response<any>>' is not assignable to type 'Promise<void>

I tried to replace the function by:

export const updateLot = functions.https.onRequest(async (req, res: Response<{ message: string }>) => { ... }

but that’s obviously not the right way as return res.status(200).json({ results: my_object }) will not compile:

Argument of type '{ results: Lot; }' is not assignable to parameter of type '{ message: string; }'.
  Object literal may only specify known properties, and 'results' does not exist in type '{ message: string; }'

I’m running out of ideas and I couldn’t find any documentation or issues on Github with similar problem.

Thanks for your help.

[Flucadetena]

In my case, if anyone comes after, I had to return void. So the same solution but instead of null, just return;

export const updateLot = functions.https.onRequest(async (req, res) => {
... some code ...

    res.status(404).json({ message: 'there was an error' })
    return;

... some code ...

    res.status(200).json({ results: my_object })
    return;
}

[jeriscc]

I am facing a similar issue. Code:

const app = express();
...
export const auditionee = functions.https.onRequest(app);

Error Message:

Argument of type 'Express' is not assignable to parameter of type '(req: Request, resp: Response<any>) => void | Promise<void>'.
  Types of parameters 'res' and 'resp' are incompatible.
    Type 'Response<any>' is not assignable to type 'Response | ServerResponse'.
      Type 'Response<any>' is missing the following properties from type 'ServerResponse': statusCode, statusMessage, writableFinished, assignSocket, and 48 more.

Firebase functions version: 3.9.0