Handle hotfix loading from GitHub Pages (#8143)

source/background.ts

@@ -10,6 +10,7 @@ import optionsStorage, {hasToken} from './options-storage.js';
 import isDevelopmentVersion from './helpers/is-development-version.js';
 import {doesBrowserActionOpenOptions} from './helpers/feature-utils.js';
 import {styleHotfixes} from './helpers/hotfix.js';
+import {fetchText} from './helpers/isomorphic-fetch.js';
 
 const {version} = chrome.runtime.getManifest();
 
@@ -34,6 +35,7 @@ handleMessages({
 	async closeTab(_: any, {tab}: chrome.runtime.MessageSender) {
 		void chrome.tabs.remove(tab!.id!);
 	},
+	fetchText,
 	async fetchJSON(url: string) {
 		const response = await fetch(url);
 		return response.json();

source/helpers/hotfix.tsx

@@ -6,6 +6,7 @@ import {any as concatenateTemplateLiteralTag} from 'code-tag';
 
 import type {RGHOptions} from '../options-storage.js';
 import isDevelopmentVersion from './is-development-version.js';
+import {isomorphicFetchText} from './isomorphic-fetch.js';
 
 const {version: currentVersion} = chrome.runtime.getManifest();
 
@@ -23,12 +24,9 @@ function parseCsv(content: string): string[][] {
 
 async function fetchHotfix(path: string): Promise<string> {
 	// Use GitHub Pages host because the API is rate-limited
-	const request = await fetch(`https://refined-github.github.io/yolo/${path}`, {
+	return isomorphicFetchText(`https://refined-github.github.io/yolo/${path}`, {
 		cache: 'no-store', // Disable caching altogether
 	});
-
-	const contents = await request.text();
-	return contents.trim();
 }
 
 type HotfixStorage = Array<[FeatureID, string, string]>;

source/helpers/isomorphic-fetch.ts

@@ -0,0 +1,16 @@
+import {isWebPage} from 'webext-detect';
+import {messageRuntime} from 'webext-msg';
+
+export async function fetchText(url: string, options: RequestInit): Promise<string> {
+	const response = await fetch(url, options);
+	return response.ok
+		? response.text()
+		: ''; // Likely a 404. Either way the response isn't the CSS we expect #8142
+}
+
+export async function isomorphicFetchText(url: string, options: RequestInit): Promise<string> {
+	return isWebPage()
+		// Firefox CSP issue: https://github.com/refined-github/refined-github/issues/8144
+		? messageRuntime({fetchString: {url, options}})
+		: fetchText(url, options);
+}