Bypassed request's referrerPolicy is reset to default

[ne2030]

Prerequisites

• I confirm my issue is not in the opened issues
• I confirm the Frequently Asked Questions didn't contain the answer to my issue

Environment check

• I'm using the latest msw version
• I'm using Node.js version 14 or higher

Browsers

Chromium (Chrome, Brave, etc.)

Reproduction repository

https://github.com/ne2030/msw-issue

Reproduction steps

1. Start a local server at root directory. For example, if you have Python on your machine you could start a server running on port 8001 using python -m SimpleHTTPServer 8001 for Python 2.x, or python3 -m http.server 8001 for Python 3.x.
2. Navigate to the local server, e.g. http://localhost:8001/
3. Open the chrome dev tool - network tab and check whether the problem is reproduced.

Reproduction repository does not use MSW directly, instead, focuses on Fetch issue.

Current behavior

Referrer policy is reset to default 'strict-origin-when-cross-origin' when the request is fetched with cloned request and custom options.

const headers = Object.fromEntries(clonedRequest.headers.entries())
delete headers['x-msw-bypass']

return fetch(clonedRequest, { headers })

Here, if any options are passed as a second argument to fetch API, then the referrer policy is reset! I don't know the exact cause of this problem, but it can be solved below.

const headers = Object.fromEntries(clonedRequest.headers.entries())

delete headers['x-msw-bypass']

return fetch(clonedRequest, { headers, referrerPolicy: request.referrerPolicy, referrer: request.referrer })

Or, I saw msw condesandbox and there, this problem is not reproduced and found out mockserviceworker.js file is different from deployed version (0.45.0). I think the version on condsandbox that creates a new Request instance and uses this directly as argument with no options at Fetch can also handle this problem.

function serializeHeaders(headers) {
  const reqHeaders = {};
  headers.forEach((value, name) => {
    reqHeaders[name] = reqHeaders[name]
      ? [].concat(reqHeaders[name]).concat(value)
      : value;
  });
  return reqHeaders;
}

const cleanRequestHeaders = serializeHeaders(clonedRequest.headers);

// Remove the bypass header to comply with the CORS preflight check.

const originalRequest = new Request(clonedRequest, {
  headers: new Headers(cleanRequestHeaders)
});

fetch(originalRequest);

The below screenshots are for reference.

Expected behavior

Preserve original option of request (especially referrerPolicy and referrer)

[ne2030]

Is there any updates on this?

[kettanaito]

Released: v2.0.0 🎉

This has been released in v2.0.0!

• 📄 Release notes
• 📦 npm package

Make sure to always update to the latest version (npm i msw@latest) to get the newest features and bug fixes.

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