Cancel request before actual request

[Couto]

What would you like to discuss?

I wasn't able to find this on the docs, nor can I find a way using the hooks features. I might be missing something.

I would like to cancel a request before it leaves my machine.

Example (this is not working, it might just better illustrate what I want to do):

import got, {
  BeforeRequestHook,
  AfterResponseHook,
  BeforeErrorHook,
  Response,
} from "got";

export default <R>(response: Response<R>) => {
  const beforeRequest: BeforeRequestHook = () => {
    throw new Error("Canceled");
  };

  const afterRequest: AfterResponseHook = () => {
    return response;
  };

  const beforeError: BeforeErrorHook = _err => {
    return response;
  };

  return got.extend({
    hooks: {
      beforeRequest: [beforeRequest],
      afterResponse: [afterRequest],
      beforeError: [beforeError],
    },
  });
};

My idea is to provide some predefined responses in some specific situations.
Any idea on how to do this?

Thanks

PS: My objective is to mock requests so it would be ideal to return the instance itself instead of using .cancel()

Checklist

• I have read the documentation.

[szmarczak]

Example (this is not working, it might just better illustrate what I want to do):

Actually this works. Throwing in a hook cancels the request.

My idea is to provide some predefined responses in some specific situations.

You can use afterResponse hook to modify the response. To provide predefined responses, you may want to set custom request option.

[Couto]

Actually this works. Throwing in a hook cancels the request.

It does in practice, but it will call the beforeError which only allows me to return an Error. So I have to .catch requests instead of just using a simple .then.

So with the goal of mocking requests, not so much.

I totally missed the request option, yeah that could actually work, will take a look.

Thank you!

[szmarczak]

@sindresorhus Should it be possible to return a response from a beforeError hook?

[sindresorhus]

@szmarczak Wouldn't it be better to allow returning a new different request from beforeRequest?

[szmarczak]

@sindresorhus You can already modify options in a beforeRequest hook. Alternatively you can pass custom request function.

Or we can allow returning IncomingMessage directly from the request function. That would be very useful e.g. when using cache (the request function would be async so await is needed to catch the ClientRequest/IncomingMessage instance). That way people could do something like this:

const request = (url, options) => new Promise((resolve, reject) => {
    const request = http.request(url, options);
    request.once('error', () => {
        resolve(createIncomingMessage());
    });

    request.once('socket', () => resolve(request));
});

await got(url, {request});

[sindresorhus]

You can already modify options in a beforeRequest hook. Alternatively you can pass custom request function.

I'm not sure how modifying options helps with canceling the request? But another use-case for being able to return IncomingMessage in beforeRequest is if you already have it cached yourself, or for prototyping when you have a static response.

Or we can allow returning IncomingMessage directly from the request function.

I wouldn't really find that useful as I don't want to override request and implement all the low-level request details myself.

[szmarczak]

But another use-case for being able to return IncomingMessage in beforeRequest is if you already have it cached yourself, or for prototyping when you have a static response.

#1051 allows to return an IncomingMessage (ResponseLike) instance using the request option. It's to make the HTTP-based caching mechanism easier to code. (I've already wrapped cacheable-request)

I'll make beforeRequest accept IncomingMessages too.

[sindresorhus]

Great 👌