sveltejs · Rich-Harris · Dec 13, 2022 · Dec 13, 2022 · Dec 13, 2022 · Dec 13, 2022
diff --git a/.changeset/witty-falcons-begin.md b/.changeset/witty-falcons-begin.md
@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+[breaking] prerender shells when ssr false and prerender not false
diff --git a/packages/kit/src/core/prerender/prerender.js b/packages/kit/src/core/prerender/prerender.js
@@ -401,7 +401,15 @@ export async function prerender() {
 				validate_common_exports(page.shared, route.id);
 			}
 
-			const prerender = get_option(nodes, 'prerender') ?? false;
+			const should_prerender = get_option(nodes, 'prerender');
+			const prerender =
+				should_prerender === true ||
+				// Try prerendering if ssr is false and no server needed. Set it to 'auto' so that
+				// the route is not removed from the manifest, there could be a server load function.
+				// People can opt out of this behavior by explicitly setting prerender to false
+				(should_prerender !== false && get_option(nodes, 'ssr') === false && !page?.server?.actions
+					? 'auto'
+					: false);
 
 			prerender_map.set(route.id, prerender);
 		}

diff --git a/packages/kit/src/runtime/server/page/index.js b/packages/kit/src/runtime/server/page/index.js
@@ -79,13 +79,37 @@ export async function render_page(event, route, page, options, state, resolve_op
 		// it's crucial that we do this before returning the non-SSR response, otherwise
 		// SvelteKit will erroneously believe that the path has been prerendered,
 		// causing functions to be omitted from the manifesst generated later
-		const should_prerender = get_option(nodes, 'prerender') ?? false;
+		const should_prerender = get_option(nodes, 'prerender');
+
 		if (should_prerender) {
 			const mod = leaf_node.server;
 			if (mod && mod.actions) {
 				throw new Error('Cannot prerender pages with actions');
 			}
 		} else if (state.prerendering) {
+			// Try to render the shell when ssr is false and prerendering not explicitly disabled.
+			// People can opt out of this behavior by explicitly setting prerender to false.
+			if (
+				should_prerender !== false &&
+				get_option(nodes, 'ssr') === false &&
+				!leaf_node.server?.actions
+			) {
+				return await render_response({
+					branch: [],
+					fetched: [],
+					page_config: {
+						ssr: false,
+						csr: get_option(nodes, 'csr') ?? true
+					},
+					status,
+					error: null,
+					event,
+					options,
+					state,
+					resolve_opts
+				});
+			}
+
 			// if the page isn't marked as prerenderable, then bail out at this point
 			return new Response(undefined, {
 				status: 204

diff --git a/packages/kit/test/prerendering/ssr-false/.gitignore b/packages/kit/test/prerendering/ssr-false/.gitignore
@@ -0,0 +1 @@
+!.env
diff --git a/packages/kit/test/prerendering/ssr-false/package.json b/packages/kit/test/prerendering/ssr-false/package.json
@@ -0,0 +1,20 @@
+{
+	"name": "prerendering-test-ssr-false",
+	"private": true,
+	"version": "0.0.2-next.0",
+	"scripts": {
+		"dev": "vite dev",
+		"build": "vite build",
+		"preview": "vite preview",
+		"test": "svelte-kit sync && pnpm build && uvu test"
+	},
+	"devDependencies": {
+		"@sveltejs/kit": "workspace:*",
+		"svelte": "^3.54.0",
+		"svelte-check": "^2.9.2",
+		"typescript": "^4.9.3",
+		"uvu": "^0.5.6",
+		"vite": "^4.0.0"
+	},
+	"type": "module"
+}
diff --git a/packages/kit/test/prerendering/ssr-false/src/app.d.ts b/packages/kit/test/prerendering/ssr-false/src/app.d.ts
@@ -0,0 +1 @@
+/// <reference types="@sveltejs/kit" />;
diff --git a/packages/kit/test/prerendering/ssr-false/src/app.html b/packages/kit/test/prerendering/ssr-false/src/app.html
@@ -0,0 +1,11 @@
+<!DOCTYPE html>
+<html lang="en">
+	<head>
+		<meta charset="utf-8" />
+		<meta name="viewport" content="width=device-width" />
+		%sveltekit.head%
+	</head>
+	<body>
+		%sveltekit.body%
+	</body>
+</html>
diff --git a/packages/kit/test/prerendering/ssr-false/src/routes/+layout.js b/packages/kit/test/prerendering/ssr-false/src/routes/+layout.js
@@ -0,0 +1 @@
+export const ssr = false;
diff --git a/packages/kit/test/prerendering/ssr-false/src/routes/not-prerenderable/+page.server.js b/packages/kit/test/prerendering/ssr-false/src/routes/not-prerenderable/+page.server.js
@@ -0,0 +1 @@
+export const actions = {};
diff --git a/packages/kit/test/prerendering/ssr-false/src/routes/not-prerenderable/+page.svelte b/packages/kit/test/prerendering/ssr-false/src/routes/not-prerenderable/+page.svelte
@@ -0,0 +1 @@
+<p>Not prerenderable because it has +page.server.js actions</p>
diff --git a/packages/kit/test/prerendering/ssr-false/src/routes/opt-out/+page.js b/packages/kit/test/prerendering/ssr-false/src/routes/opt-out/+page.js
@@ -0,0 +1 @@
+export const prerender = false;
diff --git a/packages/kit/test/prerendering/ssr-false/src/routes/opt-out/+page.svelte b/packages/kit/test/prerendering/ssr-false/src/routes/opt-out/+page.svelte
@@ -0,0 +1 @@
+<p>prerenderable shell, but opted out of prerendering explicitly</p>
diff --git a/packages/kit/test/prerendering/ssr-false/src/routes/prerenderable-2/+page.server.js b/packages/kit/test/prerendering/ssr-false/src/routes/prerenderable-2/+page.server.js
@@ -0,0 +1,3 @@
+export function load() {
+	throw new Error('I should not be called during prerendering');
+}
diff --git a/packages/kit/test/prerendering/ssr-false/src/routes/prerenderable-2/+page.svelte b/packages/kit/test/prerendering/ssr-false/src/routes/prerenderable-2/+page.svelte
@@ -0,0 +1 @@
+<p>prerenderable shell</p>
diff --git a/packages/kit/test/prerendering/ssr-false/src/routes/prerenderable/+page.js b/packages/kit/test/prerendering/ssr-false/src/routes/prerenderable/+page.js
@@ -0,0 +1,3 @@
+export function load() {
+	throw new Error('I should not be called during prerendering');
+}
diff --git a/packages/kit/test/prerendering/ssr-false/src/routes/prerenderable/+page.svelte b/packages/kit/test/prerendering/ssr-false/src/routes/prerenderable/+page.svelte
@@ -0,0 +1 @@
+<p>prerenderable shell</p>
diff --git a/packages/kit/test/prerendering/ssr-false/svelte.config.js b/packages/kit/test/prerendering/ssr-false/svelte.config.js
@@ -0,0 +1,6 @@
+/** @type {import('@sveltejs/kit').Config} */
+const config = {
+	kit: {}
+};
+
+export default config;
diff --git a/packages/kit/test/prerendering/ssr-false/test/test.js b/packages/kit/test/prerendering/ssr-false/test/test.js
@@ -0,0 +1,34 @@
+import * as fs from 'fs';
+import { fileURLToPath } from 'url';
+import { test } from 'uvu';
+import * as assert from 'uvu/assert';
+
+const build = fileURLToPath(new URL('../.svelte-kit/output/prerendered/pages', import.meta.url));
+
+/** @param {string} file */
+const read = (file, encoding = 'utf-8') => fs.readFileSync(`${build}/${file}`, encoding);
+
+test('prerenders /prerenderable shell', () => {
+	const content = read('prerenderable.html');
+	assert.ok(!content.includes('prerenderable shell'));
+});
+
+test('prerenders /prerenderable-2 shell', () => {
+	const content = read('prerenderable-2.html');
+	assert.ok(!content.includes('prerenderable shell'));
+});
+
+test('does not prerender non prerenderable things', () => {
+	assert.equal(fs.readdirSync(build).length, 2);
+});
+
+test('keeps not-explicitly-prerendered routes in the manifest', () => {
+	const manifest = fileURLToPath(
+		new URL('../.svelte-kit/output/server/manifest.js', import.meta.url)
+	);
+	const content = fs.readFileSync(manifest, 'utf-8');
+	assert.ok(content.includes('/prerenderable'));
+	assert.ok(content.includes('/prerenderable-2'));
+});
+
+test.run();
diff --git a/packages/kit/test/prerendering/ssr-false/tsconfig.json b/packages/kit/test/prerendering/ssr-false/tsconfig.json
@@ -0,0 +1,16 @@
+{
+	"compilerOptions": {
+		"allowJs": true,
+		"checkJs": true,
+		"noEmit": true,
+		"module": "esnext",
+		"moduleResolution": "node",
+		"paths": {
+			"@sveltejs/kit": ["../../../types"],
+			"$lib": ["./src/lib"],
+			"$lib/*": ["./src/lib/*"],
+			"types": ["../../../types/internal"]
+		}
+	},
+	"extends": "./.svelte-kit/tsconfig.json"
+}
diff --git a/packages/kit/test/prerendering/ssr-false/vite.config.js b/packages/kit/test/prerendering/ssr-false/vite.config.js
@@ -0,0 +1,27 @@
+import * as path from 'path';
+import { sveltekit } from '@sveltejs/kit/vite';
+
+/** @type {import('vite').UserConfig} */
+const config = {
+	build: {
+		minify: false
+	},
+
+	clearScreen: false,
+
+	logLevel: 'silent',
+
+	plugins: [sveltekit()],
+
+	define: {
+		'process.env.MY_ENV': '"MY_ENV DEFINED"'
+	},
+
+	server: {
+		fs: {
+			allow: [path.resolve('../../../src')]
+		}
+	}
+};
+
+export default config;
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		<p>Not prerenderable because it has +page.server.js actions</p>
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		<p>prerenderable shell, but opted out of prerendering explicitly</p>