feat: Fail prerendering for pages with mutative endpoints - fixes #3410 and #4252

.changeset/brave-jobs-occur.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+feat: Pages marked for prerendering fail during ssr at runtime

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

@@ -52,13 +52,15 @@ export async function load_node({
 	/** @type {import('types').LoadOutput} */
 	let loaded;
 
+	const should_prerender = node.module.prerender ?? state?.prerender?.default ?? false;
+
 	/** @type {import('types').ShadowData} */
 	const shadow = is_leaf
 		? await load_shadow_data(
 				/** @type {import('types').SSRPage} */ (route),
 				event,
 				options,
-				!!state.prerender
+				should_prerender
 		  )
 		: {};
 

packages/kit/test/apps/basics/src/routes/prerendering/__error.svelte

@@ -0,0 +1,15 @@
+<script context="module">
+	export const load = ({ error, status }) => {
+		return {
+			props: {
+				title: `${status}: ${error.message}`
+			}
+		};
+	};
+</script>
+
+<script>
+	export let title = 'Unknown error!';
+</script>
+
+<h1>{title}</h1>

packages/kit/test/apps/basics/src/routes/prerendering/mutative-endpoint.svelte

@@ -0,0 +1,5 @@
+<script context="module">
+	export const prerender = true;
+</script>
+
+<h1>I have a mutative endpoint!</h1>

packages/kit/test/apps/basics/src/routes/prerendering/mutative-endpoint.ts

@@ -0,0 +1,3 @@
+export const post = () => {
+	return {};
+};

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

@@ -1074,6 +1074,15 @@ test.describe.parallel('Errors', () => {
 		expect(response.status()).toBe(500);
 		expect(await response.text()).toMatch('thisvariableisnotdefined is not defined');
 	});
+
+	test('prerendering a page with a mutative page endpoint results in a catchable error', async ({
+		page
+	}) => {
+		await page.goto('/prerendering/mutative-endpoint');
+		expect(await page.textContent('h1')).toBe(
+			'500: Cannot prerender pages that have endpoints with mutative methods'
+		);
+	});
 });
 
 test.describe.parallel('ETags', () => {