fix: bail out of event hoisting when referencing store subscriptions

Author: trueadm

.changeset/dry-ghosts-prove.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: bail out of event hoisting when referencing store subscriptions

packages/svelte/src/compiler/phases/2-analyze/index.js

@@ -166,25 +166,20 @@ function get_delegated_event(event_name, handler, context) {
 	}
 
 	// If we can't find a function, bail-out
-	if (target_function == null) {
-		return non_hoistable;
-	}
+	if (target_function == null) return non_hoistable;
 	// If the function is marked as non-hoistable, bail-out
-	if (target_function.metadata.hoistable === 'impossible') {
-		return non_hoistable;
-	}
+	if (target_function.metadata.hoistable === 'impossible') return non_hoistable;
 	// If the function has more than one arg, then bail-out
-	if (target_function.params.length > 1) {
-		return non_hoistable;
-	}
+	if (target_function.params.length > 1) return non_hoistable;
 
 	const visited_references = new Set();
 	const scope = target_function.metadata.scope;
 	for (const [reference] of scope.references) {
 		// Bail-out if the arguments keyword is used
-		if (reference === 'arguments') {
-			return non_hoistable;
-		}
+		if (reference === 'arguments') return non_hoistable;
+		// Bail-out if references a store subscription
+		if (scope.get(`$${reference}`)?.kind === 'store_sub') return non_hoistable;
+
 		const binding = scope.get(reference);
 		const local_binding = context.state.scope.get(reference);
 
@@ -203,9 +198,7 @@ function get_delegated_event(event_name, handler, context) {
 		}
 
 		// If we reference the index within an each block, then bail-out.
-		if (binding !== null && binding.initial?.type === 'EachBlock') {
-			return non_hoistable;
-		}
+		if (binding !== null && binding.initial?.type === 'EachBlock') return non_hoistable;
 
 		if (
 			binding !== null &&

packages/svelte/tests/runtime-runes/samples/event-store-no-hoisting/_config.js

@@ -0,0 +1,26 @@
+import { flushSync } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	test({ assert, target }) {
+		const [b1, b2] = target.querySelectorAll('button');
+
+		b1.click();
+		flushSync();
+
+		assert.htmlEqual(
+			target.innerHTML,
+			'<button>set new store</button><button>incr</button><pre>0</pre>'
+		);
+
+		b2.click();
+		b2.click();
+		b2.click();
+		flushSync();
+
+		assert.htmlEqual(
+			target.innerHTML,
+			'<button>set new store</button><button>incr</button><pre>3</pre>'
+		);
+	}
+});

packages/svelte/tests/runtime-runes/samples/event-store-no-hoisting/main.svelte

@@ -0,0 +1,17 @@
+<script>
+	import { writable } from 'svelte/store';
+
+	let store = $state();
+
+	function setStore() {
+		store = writable(0, () => {
+			console.log('start');
+			return () => console.log('stop');
+		});
+	}
+</script>
+
+<button onclick={setStore}>set new store</button>
+<button onclick={() => $store++}>incr</button>
+
+<pre>{$store}</pre>