make static assets immutable (#3222)

* make static assets immutable

* write custom _headers file

* remove errant semis

* add custom headers to vercel routes config

* immutable assets in adapter-cloudflare-workers

* changesets

* tidy up

Author: Rich-Harris

.changeset/brave-weeks-allow.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+Expose appDir to adapters

.changeset/witty-meals-tie.md

@@ -0,0 +1,8 @@
+---
+'@sveltejs/adapter-cloudflare': patch
+'@sveltejs/adapter-cloudflare-workers': patch
+'@sveltejs/adapter-netlify': patch
+'@sveltejs/adapter-vercel': patch
+---
+
+Add immutable cache headers to generated assets

packages/adapter-cloudflare-workers/README.md

@@ -47,7 +47,7 @@ Now you should get some details from Cloudflare. You should get your:
 1. Account ID
 2. And your Zone-ID (Optional)
 
-Get them by visiting your Cloudflare-Dashboard and click on any domain. There, you can scroll down and on the left, you can see your details under **API**.
+Get them by visiting your [Cloudflare dashboard](https://dash.cloudflare.com) and click on any domain. There, you can scroll down and on the left, you can see your details under **API**.
 
 Then configure your sites build directory and your account-details in the config file:
 

packages/adapter-cloudflare-workers/files/entry.js

@@ -1,32 +1,54 @@
 import { App } from 'APP';
-import { manifest } from './manifest.js';
-import { getAssetFromKV, NotFoundError } from '@cloudflare/kv-asset-handler';
+import { manifest, prerendered } from './manifest.js';
+import { getAssetFromKV } from '@cloudflare/kv-asset-handler';
 
 const app = new App(manifest);
 
-addEventListener('fetch', (event) => {
+const prefix = `/${manifest.appDir}/`;
+
+addEventListener('fetch', (/** @type {FetchEvent} */ event) => {
 	event.respondWith(handle(event));
 });
 
+/**
+ * @param {FetchEvent} event
+ * @returns {Promise<Response>}
+ */
 async function handle(event) {
-	// try static files first
-	if (event.request.method == 'GET') {
-		try {
-			// TODO rather than attempting to get an asset,
-			// use the asset manifest to see if it exists
-			return await getAssetFromKV(event);
-		} catch (e) {
-			if (!(e instanceof NotFoundError)) {
-				return new Response('Error loading static asset:' + (e.message || e.toString()), {
-					status: 500
-				});
+	const { request } = event;
+
+	const url = new URL(request.url);
+
+	// generated assets
+	if (url.pathname.startsWith(prefix)) {
+		const res = await getAssetFromKV(event);
+		return new Response(res.body, {
+			headers: {
+				'cache-control': 'public, immutable, max-age=31536000',
+				'content-type': res.headers.get('content-type')
 			}
-		}
+		});
 	}
 
-	// fall back to an app route
-	const request = event.request;
+	// prerendered pages and index.html files
+	const pathname = url.pathname.replace(/\/$/, '');
+	let file = pathname.substring(1);
 
+	try {
+		file = decodeURIComponent(file);
+	} catch (err) {
+		// ignore
+	}
+
+	if (
+		manifest.assets.has(file) ||
+		manifest.assets.has(file + '/index.html') ||
+		prerendered.has(pathname || '/')
+	) {
+		return await getAssetFromKV(event);
+	}
+
+	// dynamically-generated pages
 	try {
 		const rendered = await app.render({
 			url: request.url,
@@ -38,14 +60,14 @@ async function handle(event) {
 		if (rendered) {
 			return new Response(rendered.body, {
 				status: rendered.status,
-				headers: makeHeaders(rendered.headers)
+				headers: make_headers(rendered.headers)
 			});
 		}
 	} catch (e) {
 		return new Response('Error rendering route:' + (e.message || e.toString()), { status: 500 });
 	}
 
-	return new Response({
+	return new Response('Not Found', {
 		status: 404,
 		statusText: 'Not Found'
 	});
@@ -56,11 +78,8 @@ async function read(request) {
 	return new Uint8Array(await request.arrayBuffer());
 }
 
-/**
- * @param {Record<string, string | string[]>} headers
- * @returns {Request}
- */
-function makeHeaders(headers) {
+/** @param {Record<string, string | string[]>} headers */
+function make_headers(headers) {
 	const result = new Headers();
 	for (const header in headers) {
 		const value = headers[header];

packages/adapter-cloudflare-workers/index.js

@@ -23,7 +23,7 @@ export default function () {
 			builder.rimraf(entrypoint);
 
 			builder.log.info('Prerendering static pages...');
-			await builder.prerender({
+			const { paths } = await builder.prerender({
 				dest: bucket
 			});
 
@@ -47,7 +47,7 @@ export default function () {
 				`${tmp}/manifest.js`,
 				`export const manifest = ${builder.generateManifest({
 					relativePath
-				})};\n`
+				})};\n\nexport const prerendered = new Set(${JSON.stringify(paths)});\n`
 			);
 
 			await esbuild.build({
@@ -67,6 +67,7 @@ export default function () {
 	};
 }
 
+/** @param {import('@sveltejs/kit').Builder} builder */
 function validate_config(builder) {
 	if (existsSync('wrangler.toml')) {
 		let wrangler_config;

packages/adapter-cloudflare-workers/package.json

@@ -31,6 +31,8 @@
 		"esbuild": "^0.13.15"
 	},
 	"devDependencies": {
+		"@cloudflare/kv-asset-handler": "^0.2.0",
+		"@cloudflare/workers-types": "^3.3.0",
 		"@sveltejs/kit": "workspace:*"
 	}
 }

packages/adapter-cloudflare-workers/tsconfig.json

@@ -0,0 +1,14 @@
+{
+	"compilerOptions": {
+		"allowJs": true,
+		"checkJs": true,
+		"noEmit": true,
+		"noImplicitAny": true,
+		"target": "es2020",
+		"module": "es2020",
+		"moduleResolution": "node",
+		"allowSyntheticDefaultImports": true,
+		"types": ["@cloudflare/workers-types"]
+	},
+	"include": ["./index.js", "files"]
+}

packages/adapter-cloudflare/files/worker.js

@@ -10,7 +10,20 @@ export default {
 		const url = new URL(req.url);
 
 		// static assets
-		if (url.pathname.startsWith(prefix)) return env.ASSETS.fetch(req);
+		if (url.pathname.startsWith(prefix)) {
+			/** @type {Response} */
+			const res = await env.ASSETS.fetch(req);
+
+			return new Response(res.body, {
+				headers: {
+					// include original cache headers, minus cache-control which
+					// is overridden, and etag which is no longer useful
+					'cache-control': 'public, immutable, max-age=31536000',
+					'content-type': res.headers.get('content-type'),
+					'x-robots-tag': 'noindex'
+				}
+			});
+		}
 
 		// prerendered pages and index.html files
 		const pathname = url.pathname.replace(/\/$/, '');

packages/adapter-netlify/index.js

@@ -129,7 +129,13 @@ export default function ({ split = false } = {}) {
 			builder.copy('_redirects', redirect_file);
 			appendFileSync(redirect_file, `\n\n${redirects.join('\n')}`);
 
-			// TODO write a _headers file that makes client-side assets immutable
+			builder.log.minor('Writing custom headers...');
+			const headers_file = join(publish, '_headers');
+			builder.copy('_headers', headers_file);
+			appendFileSync(
+				headers_file,
+				`\n\n/${builder.appDir}/*\n  cache-control: public\n  cache-control: immutable\n  cache-control: max-age=31536000\n`
+			);
 		}
 	};
 }

packages/adapter-vercel/index.js

@@ -68,6 +68,12 @@ export default function () {
 			writeFileSync(
 				`${dir}/config/routes.json`,
 				JSON.stringify([
+					{
+						src: `/${builder.appDir}/.+`,
+						headers: {
+							'cache-control': 'public, immutable, max-age=31536000'
+						}
+					},
 					{
 						handle: 'filesystem'
 					},

packages/kit/src/core/adapt/builder.js

@@ -32,6 +32,8 @@ export function create_builder({ cwd, config, build_data, log }) {
 		mkdirp,
 		copy,
 
+		appDir: config.kit.appDir,
+
 		createEntries(fn) {
 			generated_manifest = true;
 

packages/kit/types/config.d.ts

@@ -38,6 +38,8 @@ export interface Builder {
 	rimraf(dir: string): void;
 	mkdirp(dir: string): void;
 
+	appDir: string;
+
 	/**
 	 * Create entry points that map to individual functions
 	 * @param fn A function that groups a set of routes into an entry point