Referrer and Referrer Policy

@types/index.d.ts

@@ -71,6 +71,14 @@ export interface RequestInit {
 	 * An AbortSignal to set request's signal.
 	 */
 	signal?: AbortSignal | null;
+	/**
+	 * A string whose value is a same-origin URL, "about:client", or the empty string, to set request’s referrer.
+	 */
+	referrer?: string;
+	/**
+	 * A referrer policy to set request’s referrerPolicy.
+	 */
+	referrerPolicy?: ReferrerPolicy;
 
 	// Node-fetch extensions to the whatwg/fetch spec
 	agent?: Agent | ((parsedUrl: URL) => Agent);
@@ -115,6 +123,7 @@ declare class BodyMixin {
 export interface Body extends Pick<BodyMixin, keyof BodyMixin> {}
 
 export type RequestRedirect = 'error' | 'follow' | 'manual';
+export type ReferrerPolicy = '' | 'no-referrer' | 'no-referrer-when-downgrade' | 'same-origin' | 'origin' | 'strict-origin' | 'origin-when-cross-origin' | 'strict-origin-when-cross-origin' | 'unsafe-url';
 export type RequestInfo = string | Request;
 export class Request extends BodyMixin {
 	constructor(input: RequestInfo, init?: RequestInit);
@@ -139,6 +148,14 @@ export class Request extends BodyMixin {
 	 * Returns the URL of request as a string.
 	 */
 	readonly url: string;
+	/**
+	 * A string whose value is a same-origin URL, "about:client", or the empty string, to set request’s referrer.
+	 */
+	readonly referrer: string;
+	/**
+	 * A referrer policy to set request’s referrerPolicy.
+	 */
+	readonly referrerPolicy: ReferrerPolicy;
 	clone(): Request;
 }
 

README.md

@@ -581,8 +581,6 @@ Due to the nature of Node.js, the following properties are not implemented at th
 
 - `type`
 - `destination`
-- `referrer`
-- `referrerPolicy`
 - `mode`
 - `credentials`
 - `cache`

src/index.js

@@ -19,6 +19,7 @@ import Request, {getNodeRequestOptions} from './request.js';
 import {FetchError} from './errors/fetch-error.js';
 import {AbortError} from './errors/abort-error.js';
 import {isRedirect} from './utils/is-redirect.js';
+import {parseReferrerPolicyFromHeader} from './utils/referrer.js';
 
 export {Headers, Request, Response, FetchError, AbortError, isRedirect};
 
@@ -168,7 +169,9 @@ export default async function fetch(url, options_) {
 							method: request.method,
 							body: clone(request),
 							signal: request.signal,
-							size: request.size
+							size: request.size,
+							referrer: request.referrer,
+							referrerPolicy: request.referrerPolicy
 						};
 
 						// HTTP-redirect fetch step 9
@@ -185,6 +188,12 @@ export default async function fetch(url, options_) {
 							requestOptions.headers.delete('content-length');
 						}
 
+						// HTTP-redirect fetch step 14
+						const responseReferrerPolicy = parseReferrerPolicyFromHeader(headers);
+						if (responseReferrerPolicy) {
+							requestOptions.referrerPolicy = responseReferrerPolicy;
+						}
+
 						// HTTP-redirect fetch step 15
 						resolve(fetch(new Request(locationURL, requestOptions)));
 						finalize();

src/request.js

@@ -12,6 +12,9 @@ import Headers from './headers.js';
 import Body, {clone, extractContentType, getTotalBytes} from './body.js';
 import {isAbortSignal} from './utils/is.js';
 import {getSearch} from './utils/get-search.js';
+import {
+	validateReferrerPolicy, determineRequestsReferrer, DEFAULT_REFERRER_POLICY
+} from './utils/referrer.js';
 
 const INTERNALS = Symbol('Request internals');
 
@@ -93,12 +96,28 @@ export default class Request extends Body {
 			throw new TypeError('Expected signal to be an instanceof AbortSignal or EventTarget');
 		}
 
+		// §5.4, Request constructor steps, step 15.1
+		// eslint-disable-next-line no-eq-null, eqeqeq
+		let referrer = init.referrer == null ? input.referrer : init.referrer;
+		if (referrer === '') {
+			// §5.4, Request constructor steps, step 15.2
+			referrer = 'no-referrer';
+		} else if (referrer) {
+			// §5.4, Request constructor steps, step 15.3.1, 15.3.2
+			const parsedReferrer = new URL(referrer);
+			// §5.4, Request constructor steps, step 15.3.3, 15.3.4
+			referrer = /^about:(\/\/)?client$/.test(parsedReferrer) ? 'client' : parsedReferrer;
+		} else {
+			referrer = undefined;
+		}
+
 		this[INTERNALS] = {
 			method,
 			redirect: init.redirect || input.redirect || 'follow',
 			headers,
 			parsedURL,
-			signal
+			signal,
+			referrer
 		};
 
 		// Node-fetch-only options
@@ -108,6 +127,10 @@ export default class Request extends Body {
 		this.agent = init.agent || input.agent;
 		this.highWaterMark = init.highWaterMark || input.highWaterMark || 16384;
 		this.insecureHTTPParser = init.insecureHTTPParser || input.insecureHTTPParser || false;
+
+		// §5.4, Request constructor steps, step 16.
+		// Default is empty string per https://fetch.spec.whatwg.org/#concept-request-referrer-policy
+		this.referrerPolicy = init.referrerPolicy || input.referrerPolicy || '';
 	}
 
 	get method() {
@@ -130,6 +153,31 @@ export default class Request extends Body {
 		return this[INTERNALS].signal;
 	}
 
+	// https://fetch.spec.whatwg.org/#dom-request-referrer
+	get referrer() {
+		if (this[INTERNALS].referrer === 'no-referrer') {
+			return '';
+		}
+
+		if (this[INTERNALS].referrer === 'client') {
+			return 'about:client';
+		}
+
+		if (this[INTERNALS].referrer) {
+			return this[INTERNALS].referrer.toString();
+		}
+
+		return undefined;
+	}
+
+	get referrerPolicy() {
+		return this[INTERNALS].referrerPolicy;
+	}
+
+	set referrerPolicy(referrerPolicy) {
+		this[INTERNALS].referrerPolicy = validateReferrerPolicy(referrerPolicy);
+	}
+
 	/**
 	 * Clone this request
 	 *
@@ -150,7 +198,9 @@ Object.defineProperties(Request.prototype, {
 	headers: {enumerable: true},
 	redirect: {enumerable: true},
 	clone: {enumerable: true},
-	signal: {enumerable: true}
+	signal: {enumerable: true},
+	referrer: {enumerable: true},
+	referrerPolicy: {enumerable: true}
 });
 
 /**
@@ -186,6 +236,29 @@ export const getNodeRequestOptions = request => {
 		headers.set('Content-Length', contentLengthValue);
 	}
 
+	// 4.1. Main fetch, step 2.6
+	// > If request's referrer policy is the empty string, then set request's referrer policy to the
+	// > default referrer policy.
+	if (request.referrerPolicy === '') {
+		request.referrerPolicy = DEFAULT_REFERRER_POLICY;
+	}
+
+	// 4.1. Main fetch, step 2.7
+	// > If request's referrer is not "no-referrer", set request's referrer to the result of invoking
+	// > determine request's referrer.
+	if (request.referrer && request.referrer !== 'no-referrer') {
+		request[INTERNALS].referrer = determineRequestsReferrer(request);
+	} else {
+		request[INTERNALS].referrer = 'no-referrer';
+	}
+
+	// 4.5. HTTP-network-or-cache fetch, step 6.9
+	// > If httpRequest's referrer is a URL, then append `Referer`/httpRequest's referrer, serialized
+	// >  and isomorphic encoded, to httpRequest's header list.
+	if (request[INTERNALS].referrer instanceof URL) {
+		headers.set('Referer', request.referrer);
+	}
+
 	// HTTP-network-or-cache fetch step 2.11
 	if (!headers.has('User-Agent')) {
 		headers.set('User-Agent', 'node-fetch');