From f28d823d5ebfb27c02438285500f4464fac90593 Mon Sep 17 00:00:00 2001
From: Rich Harris <hello@rich-harris.dev>
Date: Mon, 23 May 2022 22:18:56 -0400
Subject: [PATCH] only serve _app/build with immutable cache header, not
 _app/version.json - fixes #4837

---
 .changeset/wise-berries-flash.md              | 10 ++++++++
 .../adapter-cloudflare-workers/files/entry.js |  2 +-
 packages/adapter-cloudflare/src/worker.js     |  2 +-
 packages/adapter-netlify/src/edge.js          |  3 ++-
 packages/adapter-node/src/handler.js          | 23 +++++++++++--------
 packages/adapter-vercel/index.js              |  2 +-
 6 files changed, 29 insertions(+), 13 deletions(-)
 create mode 100644 .changeset/wise-berries-flash.md

diff --git a/.changeset/wise-berries-flash.md b/.changeset/wise-berries-flash.md
new file mode 100644
index 000000000000..0e72e7394437
--- /dev/null
+++ b/.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/build with immutable cache header, not \_app/version.json
diff --git a/packages/adapter-cloudflare-workers/files/entry.js b/packages/adapter-cloudflare-workers/files/entry.js
index 2d2a5d32c0cf..2efd905e45f3 100644
--- a/packages/adapter-cloudflare-workers/files/entry.js
+++ b/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}/build/`;
 
 export default {
 	/**
diff --git a/packages/adapter-cloudflare/src/worker.js b/packages/adapter-cloudflare/src/worker.js
index ad7c4643034d..5c385749e667 100644
--- a/packages/adapter-cloudflare/src/worker.js
+++ b/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}/build/`;
 
 /** @type {import('worktop/cfw').Module.Worker<{ ASSETS: import('worktop/cfw.durable').Durable.Object }>} */
 const worker = {
diff --git a/packages/adapter-netlify/src/edge.js b/packages/adapter-netlify/src/edge.js
index 89d2eb7e58ec..adf7dee8a9b7 100644
--- a/packages/adapter-netlify/src/edge.js
+++ b/packages/adapter-netlify/src/edge.js
@@ -2,7 +2,7 @@ import { Server } from '0SERVER';
 import { manifest, prerendered } from 'MANIFEST';
 
 const server = new Server(manifest);
-const prefix = `/${manifest.appDir}/`;
+const prefix = `/${manifest.appDir}/build/`;
 
 /**
  * @param { Request } request
@@ -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/build files with an immutable cache header?
 		return;
 	}
 
diff --git a/packages/adapter-node/src/handler.js b/packages/adapter-node/src/handler.js
index d5c66d920b15..e68ed88b3b22 100644
--- a/packages/adapter-node/src/handler.js
+++ b/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}/build/`)) {
+						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)
 );
diff --git a/packages/adapter-vercel/index.js b/packages/adapter-vercel/index.js
index 041f492557fa..37d0d7dda9a8 100644
--- a/packages/adapter-vercel/index.js
+++ b/packages/adapter-vercel/index.js
@@ -180,7 +180,7 @@ async function v1(builder, external) {
 			...prerendered_pages,
 			...prerendered_redirects,
 			{
-				src: `/${builder.config.kit.appDir}/.+`,
+				src: `/${builder.config.kit.appDir}/build/.+`,
 				headers: {
 					'cache-control': 'public, immutable, max-age=31536000'
 				}