fetch: Referer header is almost never being set

[KhafraDev]

I'll get around to fixing it, but it could be a good first issue for someone who wants to dive into the code but doesn't know where to start. Here's why the bug occurs:

The referrerPolicy is being set to undefined here

undici/lib/fetch/index.js

Lines 557 to 559 in bc8e2b8

	if (request.referrerPolicy === '') {
	request.referrerPolicy = request.policyContainer.referrerPolicy
	}

because we don't implement policyContainers:

undici/lib/fetch/util.js

Lines 328 to 338 in bc8e2b8

	// https://html.spec.whatwg.org/multipage/origin.html#policy-container
	function makePolicyContainer () {
	// TODO
	return {}
	}
	// https://html.spec.whatwg.org/multipage/origin.html#clone-a-policy-container
	function clonePolicyContainer () {
	// TODO
	return {}
	}

which causes this condition to trigger

undici/lib/fetch/util.js

Lines 346 to 348 in bc8e2b8

	if (policy == null || policy === '' || policy === 'no-referrer') {
	return 'no-referrer'
	}

which means the header is never appended here

undici/lib/fetch/index.js

Lines 1333 to 1335 in bc8e2b8

	if (httpRequest.referrer instanceof URL) {
	httpRequest.headersList.append('referer', isomorphicEncode(httpRequest.referrer.href))
	}

The easiest fix is to implement makePolicyContainer and clonePolicyContainer (both are used). Follow the steps in the links above the methods (and include the steps as comments). A "list" is an array.

[Aditya-A-G]

hey, @KhafraDev I would like to work on this issue. can you please assign this issue to me

[Aditya-A-G]

sorry due to some reason I will not be able to solve this issue