fix: tighten up preloadCode (#12217)

support absolute URLs with `data-sveltekit-preload-code="viewport"` and reroutes for preloadCode in general

---------

Co-authored-by: Ben McCann <[email protected]>
Co-authored-by: Chew Tee Ming <[email protected]>
Co-authored-by: Simon H <[email protected]>

.changeset/fluffy-coats-laugh.md

@@ -0,0 +1,5 @@
+---
+"@sveltejs/kit": patch
+---
+
+fix: support absolute URLs and reroutes with `data-sveltekit-preload-code="viewport"`

packages/kit/src/runtime/client/client.js

@@ -426,9 +426,15 @@ async function _preload_data(intent) {
 	return load_cache.promise;
 }
 
-/** @param {URL} url */
+/**
+ * @param {URL} url
+ * @returns {Promise<void>}
+ */
 async function _preload_code(url) {
-	const route = routes.find((route) => route.exec(get_url_path(url)));
+	const rerouted = get_rerouted_url(url);
+	if (!rerouted) return;
+
+	const route = routes.find((route) => route.exec(get_url_path(rerouted)));
 
 	if (route) {
 		await Promise.all([...route.layouts, route.leaf].map((load) => load?.[1]()));
@@ -1189,16 +1195,11 @@ async function load_root_error_page({ status, error, url, route }) {
 }
 
 /**
- * Resolve the full info (which route, params, etc.) for a client-side navigation from the URL,
- * taking the reroute hook into account. If this isn't a client-side-navigation (or the URL is undefined),
- * returns undefined.
- * @param {URL | undefined} url
- * @param {boolean} invalidating
+ * Resolve the relative rerouted URL for a client-side navigation
+ * @param {URL} url
+ * @returns {URL | undefined}
  */
-function get_navigation_intent(url, invalidating) {
-	if (!url) return;
-	if (is_external_url(url, base, app.hash)) return;
-
+function get_rerouted_url(url) {
 	// reroute could alter the given URL, so we pass a copy
 	let rerouted;
 	try {
@@ -1225,9 +1226,26 @@ function get_navigation_intent(url, invalidating) {
 		}
 
 		// fall back to native navigation
-		return undefined;
+		return;
 	}
 
+	return rerouted;
+}
+
+/**
+ * Resolve the full info (which route, params, etc.) for a client-side navigation from the URL,
+ * taking the reroute hook into account. If this isn't a client-side-navigation (or the URL is undefined),
+ * returns undefined.
+ * @param {URL | undefined} url
+ * @param {boolean} invalidating
+ */
+function get_navigation_intent(url, invalidating) {
+	if (!url) return;
+	if (is_external_url(url, base, app.hash)) return;
+
+	const rerouted = get_rerouted_url(url);
+	if (!rerouted) return;
+
 	const path = get_url_path(rerouted);
 
 	for (const route of routes) {
@@ -1942,13 +1960,20 @@ export function preloadCode(pathname) {
 	const url = new URL(pathname, current.url);
 
 	if (DEV) {
+		if (!pathname.startsWith('/')) {
+			throw new Error(
+				'argument passed to preloadCode must be a pathname (i.e. "/about" rather than "http://example.com/about"'
+			);
+		}
+
 		if (!pathname.startsWith(base)) {
 			throw new Error(
-				`pathnames passed to preloadCode must start with \`paths.base\` (i.e. "${base}${pathname}" rather than "${pathname}")`
+				`pathname passed to preloadCode must start with \`paths.base\` (i.e. "${base}${pathname}" rather than "${pathname}")`
 			);
 		}
 
-		if (!routes.find((route) => route.exec(get_url_path(url)))) {
+		const rerouted = get_rerouted_url(url);
+		if (!rerouted || !routes.find((route) => route.exec(get_url_path(rerouted)))) {
 			throw new Error(`'${pathname}' did not match any routes`);
 		}
 	}

packages/kit/test/ambient.d.ts

@@ -16,7 +16,7 @@ declare global {
 	const preloadData: (url: string) => Promise<void>;
 	const beforeNavigate: (fn: (url: URL) => void | boolean) => void;
 	const afterNavigate: (fn: () => void) => void;
-	const preloadCode: (...urls: string[]) => Promise<void>;
+	const preloadCode: (pathname: string) => Promise<void>;
 }
 
 export {};

packages/kit/test/apps/basics/src/routes/data-sveltekit/preload-code/+page.svelte

@@ -0,0 +1,11 @@
+<div style="height: 200vh"></div>
+
+<a
+	id="viewport"
+	href="/data-sveltekit/preload-code/target/viewport"
+	data-sveltekit-preload-code="viewport">viewport</a
+>
+<a id="hover" href="/data-sveltekit/preload-code/target/hover" data-sveltekit-preload-code="hover"
+	>hover</a
+>
+<a id="tap" href="/data-sveltekit/preload-code/target/tap" data-sveltekit-preload-code="tap">tap</a>

packages/kit/test/apps/basics/src/routes/data-sveltekit/preload-code/target/eager/+page.js

@@ -0,0 +1,5 @@
+export function load() {
+	return {
+		name: 'eager'
+	};
+}

packages/kit/test/apps/basics/src/routes/data-sveltekit/preload-code/target/eager/+page.svelte

@@ -0,0 +1,5 @@
+<script>
+	export let data;
+</script>
+
+<h1>{data.name}</h1>

packages/kit/test/apps/basics/src/routes/data-sveltekit/preload-code/target/hover/+page.js

@@ -0,0 +1,5 @@
+export function load() {
+	return {
+		name: 'hover'
+	};
+}

packages/kit/test/apps/basics/src/routes/data-sveltekit/preload-code/target/hover/+page.svelte

@@ -0,0 +1,5 @@
+<script>
+	export let data;
+</script>
+
+<h1>{data.name}</h1>

packages/kit/test/apps/basics/src/routes/data-sveltekit/preload-code/target/tap/+page.js

@@ -0,0 +1,5 @@
+export function load() {
+	return {
+		name: 'tap'
+	};
+}

packages/kit/test/apps/basics/src/routes/data-sveltekit/preload-code/target/tap/+page.svelte

@@ -0,0 +1,5 @@
+<script>
+	export let data;
+</script>
+
+<h1>{data.name}</h1>

packages/kit/test/apps/basics/src/routes/data-sveltekit/preload-code/target/viewport/+page.js

@@ -0,0 +1,5 @@
+export function load() {
+	return {
+		name: 'hover'
+	};
+}

packages/kit/test/apps/basics/src/routes/data-sveltekit/preload-code/target/viewport/+page.svelte

@@ -0,0 +1,5 @@
+<script>
+	export let data;
+</script>
+
+<h1>{data.name}</h1>

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

@@ -824,6 +824,36 @@ test.describe('Invalidation', () => {
 });
 
 test.describe('data-sveltekit attributes', () => {
+	test('data-sveltekit-preload-code', async ({ page }) => {
+		/** @type {string[]} */
+		const requests = [];
+		page.on('request', (r) => {
+			requests.push(r.url());
+		});
+
+		// eager
+		await page.goto('/data-sveltekit/preload-code');
+		expect(requests.length).toBeGreaterThanOrEqual(1);
+
+		// viewport
+		requests.length = 0;
+		page.locator('#viewport').scrollIntoViewIfNeeded();
+		await Promise.all([page.waitForTimeout(100), page.waitForLoadState('networkidle')]);
+		expect(requests.length).toBeGreaterThanOrEqual(1);
+
+		// hover
+		requests.length = 0;
+		await page.locator('#hover').dispatchEvent('mousemove');
+		await Promise.all([page.waitForTimeout(100), page.waitForLoadState('networkidle')]);
+		expect(requests.length).toBeGreaterThanOrEqual(1);
+
+		// tap
+		requests.length = 0;
+		await page.locator('#tap').dispatchEvent('touchstart');
+		await Promise.all([page.waitForTimeout(100), page.waitForLoadState('networkidle')]);
+		expect(requests.length).toBeGreaterThanOrEqual(1);
+	});
+
 	test('data-sveltekit-preload-data', async ({ page }) => {
 		/** @type {string[]} */
 		const requests = [];

packages/kit/test/apps/basics/test/cross-platform/client.test.js

@@ -601,7 +601,40 @@ test.describe.serial('Errors', () => {
 });
 
 test.describe('Prefetching', () => {
-	test('prefetches programmatically', async ({ baseURL, page, app }) => {
+	test('prefetches code programmatically', async ({ page, app }) => {
+		await page.goto('/routing/a');
+
+		/** @type {string[]} */
+		const requests = [];
+		page.on('request', (r) => {
+			requests.push(r.url());
+		});
+
+		await app.preloadCode('/routing/b');
+
+		// svelte request made is environment dependent
+		if (process.env.DEV) {
+			expect(requests.filter((req) => req.endsWith('routing/b/+page.js')).length).toBe(1);
+			expect(requests.filter((req) => req.endsWith('routing/b/+page.svelte')).length).toBe(1);
+		} else {
+			expect(requests.filter((req) => /\/_app\/immutable\/nodes\/.*?.js$/.test(req)).length).toBe(
+				1
+			);
+		}
+
+		if (process.env.DEV) {
+			try {
+				await app.preloadCode('https://example.com');
+				throw new Error('Error was not thrown');
+			} catch (/** @type {any} */ e) {
+				expect(e.message).toMatch(
+					'argument passed to preloadCode must be a pathname (i.e. "/about" rather than "http://example.com/about"'
+				);
+			}
+		}
+	});
+
+	test('prefetches data programmatically', async ({ baseURL, page, app }) => {
 		await page.goto('/routing/a');
 
 		/** @type {string[]} */

packages/kit/test/utils.d.ts

@@ -18,7 +18,7 @@ export const test: TestType<
 				invalidate(url: string): Promise<void>;
 				beforeNavigate(url: URL): void | boolean;
 				afterNavigate(url: URL): void;
-				preloadCode(...urls: string[]): Promise<void>;
+				preloadCode(pathname: string): Promise<void>;
 				preloadData(url: string): Promise<void>;
 			};
 			clicknav(selector: string, options?: Parameters<Page['waitForNavigation']>[0]): Promise<void>;

packages/kit/test/utils.js

@@ -40,10 +40,10 @@ export const test = base.extend({
 			afterNavigate: () => page.evaluate(() => afterNavigate(() => {})),
 
 			/**
-			 * @param {string[]} urls
+			 * @param {string} pathname
 			 * @returns {Promise<void>}
 			 */
-			preloadCode: (...urls) => page.evaluate((urls) => preloadCode(...urls), urls),
+			preloadCode: (pathname) => page.evaluate((pathname) => preloadCode(pathname), pathname),
 
 			/**
 			 * @param {string} url