Only serve _app/immutable with immutable cache headers

.changeset/wise-berries-flash.md

@@ -0,0 +1,10 @@
+---
+'@sveltejs/adapter-cloudflare': patch
+'@sveltejs/adapter-cloudflare-workers': patch
+'@sveltejs/adapter-netlify': patch
+'@sveltejs/adapter-node': patch
+'@sveltejs/adapter-vercel': patch
+'@sveltejs/kit': patch
+---
+
+only serve `_app/immutable` with immutable cache header, not `_app/version.json`

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

@@ -6,7 +6,7 @@ const static_asset_manifest = JSON.parse(static_asset_manifest_json);
 
 const server = new Server(manifest);
 
-const prefix = `/${manifest.appDir}/`;
+const prefix = `/${manifest.appDir}/immutable/`;
 
 export default {
 	/**

packages/adapter-cloudflare/src/worker.js

@@ -4,7 +4,7 @@ import * as Cache from 'worktop/cfw.cache';
 
 const server = new Server(manifest);
 
-const prefix = `/${manifest.appDir}/`;
+const prefix = `/${manifest.appDir}/immutable/`;
 
 /** @type {import('worktop/cfw').Module.Worker<{ ASSETS: import('worktop/cfw.durable').Durable.Object }>} */
 const worker = {

packages/adapter-netlify/index.js

@@ -64,7 +64,7 @@ export default function ({ split = false, edge = edge_set_in_env_var } = {}) {
 			builder.copy('_headers', headers_file);
 			appendFileSync(
 				headers_file,
-				`\n\n/${builder.config.kit.appDir}/*\n  cache-control: public\n  cache-control: immutable\n  cache-control: max-age=31536000\n`
+				`\n\n/${builder.config.kit.appDir}/immutable/*\n  cache-control: public\n  cache-control: immutable\n  cache-control: max-age=31536000\n`
 			);
 
 			// for esbuild, use ESM

packages/adapter-netlify/src/edge.js

@@ -12,6 +12,7 @@ const prefix = `/${manifest.appDir}/`;
 export default function handler(request, context) {
 	if (is_static_file(request)) {
 		// Static files can skip the handler
+		// TODO can we serve _app/immutable files with an immutable cache header?
 		return;
 	}
 
@@ -33,6 +34,7 @@ function is_static_file(request) {
 	if (url.pathname.startsWith(prefix)) {
 		return true;
 	}
+
 	// prerendered pages and index.html files
 	const pathname = url.pathname.replace(/\/$/, '');
 	let file = pathname.substring(1);

packages/adapter-node/src/handler.js

@@ -22,18 +22,23 @@ const __dirname = path.dirname(fileURLToPath(import.meta.url));
 
 /**
  * @param {string} path
- * @param {number} max_age
- * @param {boolean} immutable
+ * @param {boolean} client
  */
-function serve(path, max_age, immutable = false) {
+function serve(path, client = false) {
 	return (
 		fs.existsSync(path) &&
 		sirv(path, {
 			etag: true,
-			maxAge: max_age,
-			immutable,
 			gzip: true,
-			brotli: true
+			brotli: true,
+			setHeaders:
+				client &&
+				((res, pathname) => {
+					// only apply to build directory, not e.g. version.json
+					if (pathname.startsWith(`/${manifest.appDir}/immutable/`)) {
+						res.setHeader('cache-control', 'public,max-age=31536000,immutable');
+					}
+				})
 		})
 	);
 }
@@ -126,9 +131,9 @@ function get_origin(headers) {
 
 export const handler = sequence(
 	[
-		serve(path.join(__dirname, '/client'), 31536000, true),
-		serve(path.join(__dirname, '/static'), 0),
-		serve(path.join(__dirname, '/prerendered'), 0),
+		serve(path.join(__dirname, '/client'), true),
+		serve(path.join(__dirname, '/static')),
+		serve(path.join(__dirname, '/prerendered')),
 		ssr
 	].filter(Boolean)
 );

packages/adapter-vercel/index.js

@@ -181,7 +181,7 @@ async function v1(builder, external) {
 			...prerendered_pages,
 			...prerendered_redirects,
 			{
-				src: `/${builder.config.kit.appDir}/.+`,
+				src: `/${builder.config.kit.appDir}/immutable/.+`,
 				headers: {
 					'cache-control': 'public, immutable, max-age=31536000'
 				}

packages/kit/src/core/build/build_client.js

@@ -59,7 +59,7 @@ export async function build_client({
 		build: {
 			cssCodeSplit: true,
 			manifest: true,
-			outDir: client_out_dir,
+			outDir: `${client_out_dir}/immutable`,
 			polyfillDynamicImport: false,
 			rollupOptions: {
 				input,
@@ -95,7 +95,9 @@ export async function build_client({
 	const { chunks, assets } = await create_build(merged_config);
 
 	/** @type {import('vite').Manifest} */
-	const vite_manifest = JSON.parse(fs.readFileSync(`${client_out_dir}/manifest.json`, 'utf-8'));
+	const vite_manifest = JSON.parse(
+		fs.readFileSync(`${client_out_dir}/immutable/manifest.json`, 'utf-8')
+	);
 
 	const entry = posixify(client_entry_file);
 	const entry_js = new Set();

packages/kit/src/core/build/build_server.js

@@ -69,7 +69,7 @@ export class Server {
 			manifest,
 			method_override: ${s(config.kit.methodOverride)},
 			paths: { base, assets },
-			prefix: assets + '/${config.kit.appDir}/',
+			prefix: assets + '/${config.kit.appDir}/immutable/',
 			prerender: {
 				default: ${config.kit.prerender.default},
 				enabled: ${config.kit.prerender.enabled}

packages/kit/src/core/build/build_service_worker.js

@@ -44,7 +44,7 @@ export async function build_service_worker(
 
 			export const build = [
 				${Array.from(build)
-					.map((file) => `${s(`${config.kit.paths.base}/${config.kit.appDir}/${file}`)}`)
+					.map((file) => `${s(`${config.kit.paths.base}/${config.kit.appDir}/immutable/${file}`)}`)
 					.join(',\n\t\t\t\t')}
 			];
 

packages/kit/src/core/build/index.js

@@ -26,15 +26,18 @@ export async function build(config, { log }) {
 
 	const { manifest_data } = sync.all(config);
 
+	// TODO this is so that Vite's preloading works. Unfortunately, it fails
+	// during `svelte-kit preview`, because we use a local asset path. If Vite
+	// used relative paths, I _think_ this could get fixed. Issue here:
+	// https://github.com/vitejs/vite/issues/2009
+	const { base, assets } = config.kit.paths;
+	const assets_base = `${assets || base}/${config.kit.appDir}/immutable/`;
+
 	const options = {
 		cwd,
 		config,
 		build_dir,
-		// TODO this is so that Vite's preloading works. Unfortunately, it fails
-		// during `svelte-kit preview`, because we use a local asset path. If Vite
-		// used relative paths, I _think_ this could get fixed. Issue here:
-		// https://github.com/vitejs/vite/issues/2009
-		assets_base: `${config.kit.paths.assets || config.kit.paths.base}/${config.kit.appDir}/`,
+		assets_base,
 		manifest_data,
 		output_dir,
 		client_entry_file: path.relative(cwd, `${get_runtime_path(config)}/client/start.js`),
@@ -65,8 +68,8 @@ export async function build(config, { log }) {
 
 	const files = new Set([
 		...static_files,
-		...client.chunks.map((chunk) => `${config.kit.appDir}/${chunk.fileName}`),
-		...client.assets.map((chunk) => `${config.kit.appDir}/${chunk.fileName}`)
+		...client.chunks.map((chunk) => `${config.kit.appDir}/immutable/${chunk.fileName}`),
+		...client.assets.map((chunk) => `${config.kit.appDir}/immutable/${chunk.fileName}`)
 	]);
 
 	// TODO is this right?

packages/kit/src/core/preview/index.js

@@ -67,8 +67,12 @@ export async function preview({ port, host, https: use_https = false }) {
 		scoped(
 			assets,
 			sirv(join(config.kit.outDir, 'output/client'), {
-				maxAge: 31536000,
-				immutable: true
+				setHeaders: (res, pathname) => {
+					// only apply to build directory, not e.g. version.json
+					if (pathname.startsWith(`/${config.kit.appDir}/immutable`)) {
+						res.setHeader('cache-control', 'public,max-age=31536000,immutable');
+					}
+				}
 			})
 		),
 

packages/kit/test/apps/basics/test/test.js

@@ -347,7 +347,7 @@ test.describe.parallel('Imports', () => {
 			]);
 		} else {
 			expect(sources[0].startsWith('data:image/png;base64,')).toBeTruthy();
-			expect(sources[1]).toBe(`${baseURL}/_app/assets/large-3183867c.jpg`);
+			expect(sources[1]).toBe(`${baseURL}/_app/immutable/assets/large-3183867c.jpg`);
 		}
 	});
 });
@@ -2649,3 +2649,13 @@ test.describe.parallel('XSS', () => {
 		);
 	});
 });
+
+test.describe.parallel('Version', () => {
+	test('does not serve version.json with an immutable cache header', async ({ request }) => {
+		// this isn't actually a great test, because caching behaviour is down to adapters.
+		// but it's better than nothing
+		const response = await request.get('/_app/version.json');
+		const headers = response.headers();
+		expect(headers['cache-control'] || '').not.toContain('immutable');
+	});
+});