requests with cookies

[till]

Hey,

I have a weird situation where I started using MSW to mock out requests in tests (through the server implementation) and then tried to proceed to use the same mocks for my frontend (while developing the app).

There's a weird case where I do requests which are not mocked and MSW picks up (see it in the developer console) on them (letting me know about the request and suggests to add a handler). These requests are not supposed to be mocked and I want them to hit another backend.

Now on to the problem: it seems that the requests I don't want mocked hit my backend service, but they no longer include the cookie header anymore when they hit my backend. This is part of an SDK which uses Axios.

The problem is probably in my own code somewhere as I have been unable to re-produce it with an extracted test case, but I figured, I would ask here if there's anything obvious in the configuration of MSW (or otherwise), that would prevent cookies to work in these scenarios. Or if there's generally a problem with Axios as I saw a couple tickets.

For clarity:

• http://ui.some.host - my app (mostly SPA, SvelteKit based)
• http://api.some.host - my API service, I want these mocked
• http://auth.some.host - auth service, I want these to proceed (always)

I guess, related to this, is there a way to tell MSW to ignore requests to a certain domain (or URL) so I don't see the messages at all? Or silence them?

After spending a few days on this, I started rebuilding the code in another branch and so far stayed away from the issue, but I am also not yet back to where I was mocking some of my frontend requests.

[kettanaito]

Hi, @till. Happy to hear from you.

There's a weird case where I do requests which are not mocked and MSW picks up (see it in the developer console) on them (letting me know about the request and suggests to add a handler). These requests are not supposed to be mocked and I want them to hit another backend.

MSW warns on any requests that you haven't mocked to guard you against typos and unintended passthrough requests. You can disable that warning or have a custom logic around it using the onUnhandledRequest option.

worker.start({ onUnhandledRequest: 'bypass' })

You can also use this option to ignore bypassed requests to certain domains:

worker.start({
  onUnhandledRequest(request, print) {
    // Never warn about unhandled requests sent to the "*.some.host" destination.
    if (request.url.hostname.endsWith('.some.host')) {
      return
    }

    print.warning()
  }
})

Now on to the problem: it seems that the requests I don't want mocked hit my backend service, but they no longer include the cookie header anymore when they hit my backend.

I don't think this is MSW. We don't modify the bypassed requests in any way so your backend should receive exactly what you're sending from the client.

You can triage this quite easily:

1. Disable MSW. Are the cookies sent now? If yes, please create a reproduction repo, and let's fix that together.
2. With MSW enabled, go to your "Network" tab in the browser DevTools, find the request with missing cookies, inspect it. Is the Cookies header there?
3. Double-check on your credentials and cookie security policies so you're actually allowed to send cookies across different hostnames.

[aristofun]

yes, this smells like some dependency down the tree, but the gist of it is
vitest test case with latext axios + https://www.npmjs.com/package/tough-cookie hitting latest fastify 5.* server started on localhost from the same vitest process - works fine with MSW 2.4.3, but not with 2.4.4+

I'll try to narrow it down when I have capacity.

[aristofun]

so far I remove Fastify from the equation - even raw node:http server doesn't receive cookie header in bypassed request

[aristofun]

Okay I finally created a minimal example:
https://codesandbox.io/p/devbox/8qvlj6

Change the msw version to 2.4.3 reinstall and yarn start to see the difference.

I don't think I have capacity nor expertise to take it further, but I would be truly grateful if you can fix it.

[aristofun]

#2338

[kettanaito]

Thanks for making a repo for it! Will take a look when I have a minute.