fix: correctly cleanup unowned derived dependency memory (#10280)

* fix: correctly cleanup unowned derived dependency memory

* recursive

* recursive

.changeset/three-camels-sell.md

@@ -0,0 +1,5 @@
+---
+"svelte": patch
+---
+
+fix: correctly cleanup unowned derived dependency memory

packages/svelte/src/internal/client/runtime.js

@@ -498,6 +498,7 @@ function destroy_references(signal) {
 			if ((reference.f & IS_EFFECT) !== 0) {
 				destroy_signal(reference);
 			} else {
+				destroy_references(reference);
 				remove_consumers(reference, 0);
 				reference.d = null;
 			}
@@ -823,6 +824,7 @@ export async function tick() {
 function update_derived(signal, force_schedule) {
 	const previous_updating_derived = updating_derived;
 	updating_derived = true;
+	destroy_references(signal);
 	const value = execute_signal_fn(signal);
 	updating_derived = previous_updating_derived;
 	const status = current_skip_consumer || (signal.f & UNOWNED) !== 0 ? DIRTY : CLEAN;
@@ -1304,8 +1306,8 @@ export function derived(init) {
 	signal.i = init;
 	signal.x = current_component_context;
 	signal.e = default_equals;
-	if (!is_unowned) {
-		push_reference(/** @type {import('./types.js').EffectSignal} */ (current_effect), signal);
+	if (current_consumer !== null) {
+		push_reference(current_consumer, signal);
 	}
 	return signal;
 }

packages/svelte/tests/signals/test.ts

@@ -1,5 +1,6 @@
 import { describe, assert, it } from 'vitest';
 import * as $ from '../../src/internal/client/runtime';
+import type { ComputationSignal } from '../../src/internal/client/types';
 
 /**
  * @param runes runes mode
@@ -199,6 +200,38 @@ describe('signals', () => {
 		};
 	});
 
+	test('correctly cleanup onowned nested derived values', () => {
+		return () => {
+			const nested: ComputationSignal<string>[] = [];
+
+			const a = $.source(0);
+			const b = $.source(0);
+			const c = $.derived(() => {
+				const a_2 = $.derived(() => $.get(a) + '!');
+				const b_2 = $.derived(() => $.get(b) + '?');
+				nested.push(a_2, b_2);
+
+				return { a: $.get(a_2), b: $.get(b_2) };
+			});
+
+			$.get(c);
+
+			$.flushSync(() => $.set(a, 1));
+
+			$.get(c);
+
+			$.flushSync(() => $.set(b, 1));
+
+			$.get(c);
+
+			// Ensure we're not leaking dependencies
+			assert.deepEqual(
+				nested.slice(0, -2).map((s) => s.d),
+				[null, null, null, null]
+			);
+		};
+	});
+
 	// outside of test function so that they are unowned signals
 	let count = $.source(0);
 	let calc = $.derived(() => {