fix: preload links if href changes (#15191)

* test

* fix

* changeset

Author: PatrickG

.changeset/small-coins-show.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+fix: preload links if href changes

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

@@ -1860,8 +1860,8 @@ if (import.meta.hot) {
 function setup_preload() {
 	/** @type {NodeJS.Timeout} */
 	let mousemove_timeout;
-	/** @type {Element} */
-	let current_a;
+	/** @type {{ element: Element | SVGAElement | undefined; href: string | SVGAnimatedString | undefined }} */
+	let current_a = { element: undefined, href: undefined };
 	/** @type {PreloadDataPriority} */
 	let current_priority;
 
@@ -1903,7 +1903,8 @@ function setup_preload() {
 		const a = find_anchor(element, container);
 
 		// we don't want to preload data again if the user has already hovered/tapped
-		const interacted = a === current_a && priority >= current_priority;
+		const interacted =
+			a === current_a.element && a?.href === current_a.href && priority >= current_priority;
 		if (!a || interacted) return;
 
 		const { url, external, download } = get_link_info(a, base, app.hash);
@@ -1916,7 +1917,7 @@ function setup_preload() {
 		if (options.reload || same_url) return;
 
 		if (priority <= options.preload_data) {
-			current_a = a;
+			current_a = { element: a, href: a.href };
 			// we don't want to preload data again on tap if we've already preloaded it on hover
 			current_priority = PRELOAD_PRIORITIES.tap;
 
@@ -1938,7 +1939,7 @@ function setup_preload() {
 				void _preload_data(intent);
 			}
 		} else if (priority <= options.preload_code) {
-			current_a = a;
+			current_a = { element: a, href: a.href };
 			current_priority = priority;
 			void _preload_code(/** @type {URL} */ (url));
 		}

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

@@ -1,3 +1,7 @@
+<script>
+	let x = 0;
+</script>
+
 <a id="one" href="/data-sveltekit/preload-data/target" data-sveltekit-preload-data>one</a>
 
 <div data-sveltekit-preload-data>
@@ -15,3 +19,8 @@
 	data-sveltekit-preload-code="hover"
 	data-sveltekit-preload-data="tap">hover for code then tap for data</a
 >
+
+<a id="dynamic" data-sveltekit-preload-data="hover" href="/data-sveltekit/preload-data/target?x={x}"
+	>dynamic</a
+>
+<button id="change_dynamic" type="button" on:click={() => x++}>change dynamic</button>

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

@@ -979,6 +979,33 @@ test.describe('data-sveltekit attributes', () => {
 			page.waitForLoadState('networkidle') // wait for preloading to finish
 		]);
 		expect(requests.length).toBe(2);
+
+		requests.length = 0;
+		await page.goto('/data-sveltekit/preload-data');
+		await page.locator('#dynamic').hover();
+		await page.locator('#dynamic').dispatchEvent('touchstart');
+		await Promise.all([
+			page.waitForTimeout(100), // wait for preloading to start
+			page.waitForLoadState('networkidle') // wait for preloading to finish
+		]);
+		expect(requests.length).toBe(2);
+		await page.waitForTimeout(100);
+		await page.locator('#dynamic').hover();
+		await page.locator('#dynamic').dispatchEvent('touchstart');
+		await Promise.all([
+			page.waitForTimeout(100), // wait for preloading to start
+			page.waitForLoadState('networkidle') // wait for preloading to finish
+		]);
+		expect(requests.length).toBe(2);
+		await page.locator('#change_dynamic').click();
+		await page.waitForTimeout(100);
+		await page.locator('#dynamic').hover();
+		await page.locator('#dynamic').dispatchEvent('touchstart');
+		await Promise.all([
+			page.waitForTimeout(100), // wait for preloading to start
+			page.waitForLoadState('networkidle') // wait for preloading to finish
+		]);
+		expect(requests.length).toBe(3);
 	});
 
 	test('data-sveltekit-preload-data network failure does not trigger navigation', async ({