fix handler SSRed into attribute

Author: 7nik

packages/svelte/src/internal/server/index.js

@@ -184,6 +184,7 @@ export function spread_attributes(attrs, css_hash, classes, styles, flags = 0) {
 	for (name in attrs) {
 		// omit functions, internal svelte properties and invalid attribute names
 		if (typeof attrs[name] === 'function') continue;
+		if (name[0] === 'o' && name[1] === 'n' && typeof attrs[name] === 'object') continue;
 		if (name[0] === '$' && name[1] === '$') continue; // faster than name.startsWith('$$')
 		if (INVALID_ATTR_NAME_CHAR_REGEX.test(name)) continue;
 

packages/svelte/tests/runtime-runes/samples/event-handler-object-ssr/_config.js

@@ -0,0 +1,10 @@
+import { test } from '../../test';
+
+export default test({
+	test({ assert, target }) {
+		assert.htmlEqual(
+			target.innerHTML,
+			`<button>a</button><button>b</button><button>c</button><button>d</button>`
+		);
+	}
+});

packages/svelte/tests/runtime-runes/samples/event-handler-object-ssr/child.svelte

@@ -0,0 +1,6 @@
+<script>
+    const props = $props();
+</script>
+
+<button onclick={props.onclick}>c</button>
+<button {...props}>d</button>

packages/svelte/tests/runtime-runes/samples/event-handler-object-ssr/main.svelte

@@ -0,0 +1,12 @@
+<script>
+	import Child from "./child.svelte";
+
+	const onclick = {
+		handleEvent() {}
+	};
+</script>
+
+<button {onclick}>a</button>
+<button {...{onclick}}>b</button>
+
+<Child {onclick} />