fix: capturing the correct event names in set_attributes

.changeset/happy-dogs-jump.md

@@ -0,0 +1,5 @@
+---
+"svelte": patch
+---
+
+fix: capture the correct event names when spreading attributes

packages/svelte/src/internal/client/dom/elements/attributes.js

@@ -158,7 +158,8 @@ export function set_attributes(element, prev, next, lowercase_attributes, css_ha
 	/** @type {Array<[string, any, () => void]>} */
 	var events = [];
 
-	for (key in next) {
+	// since key is captured we use const
+	for (const key in next) {
 		// let instead of var because referenced in a closure
 		let value = next[key];
 		if (value === prev?.[key]) continue;

packages/svelte/tests/runtime-runes/samples/event-attribute-after-spread-2/_config.js

@@ -0,0 +1,16 @@
+import { flushSync } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	test({ assert, target }) {
+		const div = target.querySelector('div');
+
+		div?.dispatchEvent(new Event('b'));
+		flushSync();
+		assert.htmlEqual(target.innerHTML, '<div>b</div>');
+
+		div?.dispatchEvent(new Event('a'));
+		flushSync();
+		assert.htmlEqual(target.innerHTML, '<div>a</div>');
+	}
+});

packages/svelte/tests/runtime-runes/samples/event-attribute-after-spread-2/main.svelte

@@ -0,0 +1,8 @@
+<script lang="ts">
+	const props = {};
+	let changed = $state('');
+</script>
+
+<div {...props} ona={() => (changed = 'a')} onb={() => (changed = 'b')}>
+	{changed}
+</div>