Return 404s from fetch in load during prerender (#4324)

* return 404 for missing fetched content during prerendering

* changeset

.changeset/stale-dogs-rule.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+Return 404 when fetching missing data during prerender

packages/kit/src/runtime/server/index.js

@@ -259,6 +259,10 @@ export async function respond(request, options, state = {}) {
 					});
 				}
 
+				if (state.prerender) {
+					return new Response('not found', { status: 404 });
+				}
+
 				// we can't load the endpoint from our own manifest,
 				// so we need to make an actual HTTP request
 				return await fetch(request);

packages/kit/src/runtime/server/page/load_node.js

@@ -190,7 +190,8 @@ export async function load_node({
 
 					response = await respond(new Request(new URL(requested, event.url).href, opts), options, {
 						fetched: requested,
-						initiator: route
+						initiator: route,
+						prerender: state.prerender
 					});
 
 					if (state.prerender) {

packages/kit/test/prerendering/basics/src/routes/fetch-404.svelte

@@ -0,0 +1,17 @@
+<script context="module">
+	/** @type {import('./fetch-404').Load} */
+	export async function load({ fetch }) {
+		const { status } = await fetch('/missing.json');
+
+		return {
+			props: { status }
+		};
+	}
+</script>
+
+<script>
+	/** @type {number} */
+	export let status;
+</script>
+
+<h1>status: {status}</h1>

packages/kit/test/prerendering/basics/test/test.js

@@ -109,4 +109,9 @@ test('prerendering is set to true in global code of hooks.js', () => {
 	assert.ok(content.includes('<h1>prerendering: true/true</h1>'), content);
 });
 
+test('fetching missing content results in a 404', () => {
+	const content = read('fetch-404.html');
+	assert.ok(content.includes('<h1>status: 404</h1>'), content);
+});
+
 test.run();