3 files changed, 35 insertions, 23 deletions

diff --git a/source/background.ts b/source/background.ts
index 6cca0d7f..f1fa00ec 100644
--- a/source/background.ts
+++ b/source/background.ts
@@ -3,17 +3,37 @@ import cache from 'webext-storage-cache'; // Also needed to regularly clear the
 import addDomainPermissionToggle from 'webext-domain-permission-toggle';
 import './options-storage';
 
-browser.runtime.onMessage.addListener((message, {tab}) => {
-	if (Array.isArray(message?.openUrls)) {
-		for (const [i, url] of (message.openUrls as string[]).entries()) {
+// GitHub Enterprise support
+addDomainPermissionToggle();
+
+const messageHandlers = {
+	openUrls(urls: string[], {tab}: browser.runtime.MessageSender) {
+		for (const [i, url] of urls.entries()) {
 			void browser.tabs.create({
 				url,
 				index: tab!.index + i + 1,
 				active: false
 			});
 		}
-	} else if (message?.closeTab) {
+	},
+	closeTab(_: any, {tab}: browser.runtime.MessageSender) {
 		void browser.tabs.remove(tab!.id!);
+	},
+	async fetch(url: string) {
+		const response = await fetch(url);
+		return response.text();
+	},
+	async fetchJSON(url: string) {
+		const response = await fetch(url);
+		return response.json();
+	}
+};
+
+browser.runtime.onMessage.addListener((message, sender) => {
+	for (const id of Object.keys(message ?? {}) as Array<keyof typeof messageHandlers>) {
+		if (id in messageHandlers) {
+			return messageHandlers[id](message[id], sender);
+		}
 	}
 });
 
@@ -41,14 +61,3 @@ browser.runtime.onInstalled.addListener(async ({reason}) => {
 	// Hope that the feature was fixed in this version
 	await cache.delete('hotfix');
 });
-
-// GitHub Enterprise support
-addDomainPermissionToggle();
-
-// `background` fetch required to avoid avoid CORB introduced in Chrome 73 https://chromestatus.com/feature/5629709824032768
-// Don’t turn this into an `async` function https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/API/runtime/onMessage#addListener_syntax
-browser.runtime.onMessage.addListener((message): Promise<string> | void => {
-	if (message?.request) {
-		return fetch(message.request).then(async response => response.text());
-	}
-});
diff --git a/source/features/embed-gist-inline.tsx b/source/features/embed-gist-inline.tsx
index 10b9c203..13fc2022 100644
--- a/source/features/embed-gist-inline.tsx
+++ b/source/features/embed-gist-inline.tsx
@@ -19,16 +19,15 @@ async function embedGist(link: HTMLAnchorElement): Promise<void> {
 	link.after(info);
 
 	try {
-		// Get the gist via background.js due to CORB policies introduced in Chrome 73
-		const gistData = await browser.runtime.sendMessage({request: `${link.href}.json`});
-
-		const files = domify.one(JSON.parse(gistData).div)!;
-		const fileCount = files.children.length;
+		// Fetch via background.js due to CORB policies
+		const gistData = await browser.runtime.sendMessage({fetchJSON: `${link.href}.json`});
 
+		const fileCount: number = gistData.files.length;
 		if (fileCount > 1) {
 			info.textContent = ` (${fileCount} files)`;
 		} else {
-			link.parentElement!.attachShadow({mode: 'open'}).append(
+			const container = <div/>;
+			container.attachShadow({mode: 'open'}).append(
 				<style>{`
 					.gist .gist-data {
 						max-height: 16em;
@@ -37,8 +36,10 @@ async function embedGist(link: HTMLAnchorElement): Promise<void> {
 				`}
 				</style>,
 				<link rel="stylesheet" href={gistData.stylesheet}/>,
-				files
+				domify.one(gistData.div)!
 			);
+			link.parentElement!.after(container);
+			info.remove();
 		}
 	} catch {
 		info.remove();
diff --git a/source/features/view-markdown-source.tsx b/source/features/view-markdown-source.tsx
index b1aaeab4..20ac64f4 100644
--- a/source/features/view-markdown-source.tsx
+++ b/source/features/view-markdown-source.tsx
@@ -15,7 +15,9 @@ import {buildRepoURL} from '../github-helpers';
 const lineActions = onetime(async () => {
 	// Avoid having to create the entire 60 lines of JSX. The URL is hardcoded to a file we know the DOM exists.
 	const randomKnownFile = 'https://github.com/sindresorhus/refined-github/blob/b1229bbaeb8cf071f0711bc2ed1b40dd96cd7a05/.editorconfig';
-	const html = await browser.runtime.sendMessage({request: randomKnownFile});
+
+	// Fetch background.js due to CORB policies
+	const html = await browser.runtime.sendMessage({fetch: randomKnownFile});
 	const blobToolbar = domify(html).querySelector('.BlobToolbar')!;
 	select('a#js-view-git-blame', blobToolbar)!.href = new GitHubURL(location.href).assign({route: 'blame'}).href;
 	select('a#js-new-issue', blobToolbar)!.href = buildRepoURL('issues/new');