fix: correctly handle SvelteDate methods with arguments (#12738)

* fix: correctly handle SvelteDate methods with arguments

* tweak

* Update packages/svelte/src/reactivity/date.js

* Update packages/svelte/src/reactivity/date.js

Co-authored-by: Rich Harris <rich.harris@vercel.com>

* Update packages/svelte/src/reactivity/date.test.ts

---------

Co-authored-by: Rich Harris <rich.harris@vercel.com>

Author: trueadm

.changeset/dirty-pens-look.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: correctly handle SvelteDate methods with arguments

packages/svelte/src/reactivity/date.js

@@ -32,6 +32,14 @@ export class SvelteDate extends Date {
 			if (method.startsWith('get') || method.startsWith('to')) {
 				// @ts-ignore
 				proto[method] = function (...args) {
+					// don't memoize if there are arguments
+					// @ts-ignore
+					if (args.length > 0) {
+						get(this.#time);
+						// @ts-ignore
+						return date_proto[method].apply(this, args);
+					}
+
 					var d = this.#deriveds.get(method);
 
 					if (d === undefined) {

packages/svelte/src/reactivity/date.test.ts

@@ -555,6 +555,30 @@ test('Date fine grained tests', () => {
 	cleanup();
 });
 
+test('Date.toLocaleString', () => {
+	const date = new SvelteDate(initial_date);
+
+	const log: any = [];
+
+	const cleanup = effect_root(() => {
+		render_effect(() => {
+			log.push(date.toLocaleString(undefined, { month: 'long', year: 'numeric' }));
+		});
+		render_effect(() => {
+			log.push(date.toLocaleString(undefined, { month: 'long' }));
+		});
+	});
+
+	flushSync();
+
+	assert.deepEqual(log, [
+		initial_date.toLocaleString(undefined, { month: 'long', year: 'numeric' }),
+		initial_date.toLocaleString(undefined, { month: 'long' })
+	]);
+
+	cleanup();
+});
+
 test('Date.instanceOf', () => {
 	assert.equal(new SvelteDate() instanceof Date, true);
 });