fix: pass all the args to custom renderer events

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

@@ -69,15 +69,17 @@ export function create_event(event_name, dom, handler, options = {}) {
 
 	/**
 	 * @this {EventTarget}
+	 * @param  {...any} args
 	 */
-	function target_handler(/** @type {Event} */ event) {
+	function target_handler(...args) {
 		if (is_custom_renderer) {
 			// Custom renderers don't use DOM event propagation/delegation,
 			// so just call the handler directly
 			return without_reactive_context(() => {
-				return handler?.call(this, event);
+				return handler?.apply(this, /** @type {any} */ (args));
 			});
 		}
+		var event = /** @type {Event} */ (args[0]);
 		if (!options.capture) {
 			// Only call in the bubble phase, else delegated events would be called before the capturing events
 			handle_event_propagation.call(dom, event);

packages/svelte/tests/custom-renderers/samples/event-handler-no-propagation/_config.js

@@ -11,14 +11,14 @@ export default test({
 		const listeners = button.listeners?.click;
 		assert.ok(listeners, 'button should have click listeners');
 
-		// Call the handler with a plain object that is NOT a DOM Event.
-		// If handle_event_propagation is called, it will fail because
-		// it tries to access DOM-specific properties like composedPath, ownerDocument, etc.
+		// Call the handler with multiple arguments.
+		// Custom renderers may pass multiple arguments to event handlers,
+		// so we need to make sure all arguments are forwarded.
 		for (const { handler } of listeners) {
-			handler.call(button, { type: 'click' });
+			handler.call(button, { type: 'click' }, 'extra', 42);
 		}
 		flushSync();
 
-		assert.deepEqual(logs, [{ type: 'click' }]);
+		assert.deepEqual(logs, [{ type: 'click' }, 'extra', 42]);
 	}
 });

packages/svelte/tests/custom-renderers/samples/event-handler-no-propagation/main.svelte

@@ -1,6 +1,6 @@
 <script>
-	function increment(e) {
-		console.log(e);
+	function increment(...args) {
+		console.log(...args);
 	}
 </script>