pass accept headers when fetching resources

extension/lib/single-file/fetch/content/content-fetch.js

@@ -21,10 +21,11 @@
  *   Source.
  */
 
-/* global browser, window, CustomEvent, setTimeout */
+/* global browser, window, CustomEvent, setTimeout, Headers */
 
 const FETCH_REQUEST_EVENT = "single-file-request-fetch";
 const FETCH_RESPONSE_EVENT = "single-file-response-fetch";
+const ACCEPT_HEADER = "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8";
 const HOST_FETCH_MAX_DELAY = 5000;
 const addEventListener = (type, listener, options) => window.addEventListener(type, listener, options);
 const dispatchEvent = event => window.dispatchEvent(event);
@@ -39,7 +40,7 @@ browser.runtime.onMessage.addListener(message => {
 
 async function onMessage(message) {
 	try {
-		let response = await fetch(message.url, { cache: "force-cache" });
+		let response = await fetch(message.url, { cache: "force-cache", headers: { accept: ACCEPT_HEADER } });
 		if (response.status == 401 || response.status == 403 || response.status == 404) {
 			response = await Promise.race(
 				[
@@ -66,7 +67,7 @@ export {
 
 async function fetchResource(url, options = {}) {
 	try {
-		let response = await fetch(url, { cache: "force-cache" });
+		let response = await fetch(url, { cache: "force-cache", headers: new Headers({ accept: ACCEPT_HEADER }) });
 		if (response.status == 401 || response.status == 403 || response.status == 404) {
 			response = await hostFetch(url);
 		}

lib/single-file/processors/hooks/content/content-hooks-web.js

@@ -21,12 +21,13 @@
  *   Source.
  */
 
-/* global window, globalThis */
+/* global window, globalThis, Headers */
 
 (globalThis => {
 
 	const FETCH_REQUEST_EVENT = "single-file-request-fetch";
 	const FETCH_RESPONSE_EVENT = "single-file-response-fetch";
+	const ACCEPT_HEADER = "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8";
 
 	const CustomEvent = globalThis.CustomEvent;
 	const fetch = globalThis.fetch;
@@ -37,7 +38,7 @@
 		const url = event.detail;
 		let detail;
 		try {
-			const response = await fetch(url, { cache: "force-cache" });
+			const response = await fetch(url, { cache: "force-cache", headers: new Headers({ accept: ACCEPT_HEADER }) });
 			detail = { url, response: await response.arrayBuffer(), headers: [...response.headers], status: response.status };
 		} catch (error) {
 			detail = { url, error: error && error.toString() };