fix: abort deriveds own AbortSignal when it disconnects (#18400)

Fixes https://github.com/sveltejs/svelte/issues/18301

---------

Co-authored-by: Fedor Nezhivoi <f.nezhivoi@corp.vk.com>
Co-authored-by: Simon H <5968653+dummdidumm@users.noreply.github.com>
Co-authored-by: Simon Holthausen <simon.holthausen@vercel.com>

.changeset/early-crabs-rest.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: abort deriveds own AbortSignal when it disconnects

packages/svelte/src/internal/client/reactivity/deriveds.js

@@ -28,6 +28,7 @@ import {
 	skipped_deps,
 	new_deps
 } from '../runtime.js';
+import { without_reactive_context } from '../dom/elements/bindings/shared.js';
 import { equals, safe_equals } from './equality.js';
 import * as e from '../errors.js';
 import * as w from '../warnings.js';
@@ -450,14 +451,18 @@ export function freeze_derived_effects(derived) {
 		// if the effect has a teardown function or abort signal, call it
 		if (e.teardown || e.ac) {
 			e.teardown?.();
-			e.ac?.abort(STALE_REACTION);
+			if (e.ac !== null) {
+				without_reactive_context(() => {
+					/** @type {AbortController} */ (e.ac).abort(STALE_REACTION);
+					e.ac = null;
+				});
+			}
 
 			// make it a noop so it doesn't get called again if the derived
 			// is unfrozen. we don't set it to `null`, because the existence
 			// of a teardown function is what determines whether the
 			// effect runs again during unfreezing (but not for teardown-only effects)
 			if (e.fn !== null) e.teardown = noop;
-			e.ac = null;
 
 			remove_reactions(e, 0);
 			destroy_effect_children(e);

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

@@ -408,6 +408,14 @@ function remove_reaction(signal, dependency) {
 			update_derived_status(derived);
 		}
 
+		// Call abort controller, noone's listening to this derived anymore
+		if (derived.ac !== null) {
+			without_reactive_context(() => {
+				/** @type {AbortController} */ (derived.ac).abort(STALE_REACTION);
+				derived.ac = null;
+			});
+		}
+
 		// freeze any effects inside this derived
 		freeze_derived_effects(derived);
 

packages/svelte/tests/runtime-runes/samples/abort-signal-derived-destroy/Child.svelte

@@ -0,0 +1,20 @@
+<script lang="ts">
+	import { getAbortSignal } from "svelte";
+
+	let { count, aborted = $bindable() } = $props()
+
+	let der = $derived.by(()=>{
+		const signal = getAbortSignal();
+
+		signal.addEventListener("abort", () => {
+			try {
+				aborted++;
+			} catch(e) {
+				console.error(e);
+			}
+		});
+		return count;
+	})
+</script>
+
+{der}

packages/svelte/tests/runtime-runes/samples/abort-signal-derived-destroy/_config.js

@@ -0,0 +1,14 @@
+import { ok, test } from '../../test';
+import { flushSync } from 'svelte';
+
+export default test({
+	async test({ assert, target, errors }) {
+		const btn = target.querySelector('button');
+
+		flushSync(() => {
+			btn?.click();
+		});
+		assert.htmlEqual(target.innerHTML, '1 <button>increment</button>');
+		assert.deepEqual(errors, []);
+	}
+});

packages/svelte/tests/runtime-runes/samples/abort-signal-derived-destroy/main.svelte

@@ -0,0 +1,14 @@
+<script lang="ts">
+	import Child from './Child.svelte'
+
+	let count = $state(0);
+	let aborted = $state(0)
+</script>
+
+{aborted}
+
+<button onclick={() => count++}>increment</button>
+
+{#if count % 2 === 0}
+	<Child {count} bind:aborted={aborted} />
+{/if}

packages/svelte/tests/runtime-runes/samples/abort-signal-derived-set-state/_config.js

@@ -4,9 +4,11 @@ import { flushSync } from 'svelte';
 export default test({
 	async test({ assert, target, errors }) {
 		const btn = target.querySelector('button');
+
 		flushSync(() => {
 			btn?.click();
 		});
+		assert.htmlEqual(target.innerHTML, '1:1 <button></button>');
 		assert.deepEqual(errors, []);
 	}
 });

packages/svelte/tests/runtime-runes/samples/abort-signal-derived-set-state/main.svelte

@@ -19,6 +19,6 @@
 	})
 </script>
 
-{der}
+{der}:{aborted}
 
 <button onclick={() => count++}></button>