fix: improve deep_read performance (#10624)

.changeset/wise-apples-care.md

@@ -0,0 +1,5 @@
+---
+"svelte": patch
+---
+
+fix: improve deep_read performance

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

@@ -1929,12 +1929,12 @@ export function out(dom, get_transition_fn, props, global = false) {
 export function action(dom, action, value_fn) {
 	/** @type {undefined | import('./types.js').ActionPayload<P>} */
 	let payload = undefined;
+	let needs_deep_read = false;
 	// Action could come from a prop, therefore could be a signal, therefore untrack
 	// TODO we could take advantage of this and enable https://github.com/sveltejs/svelte/issues/6942
 	effect(() => {
 		if (value_fn) {
 			const value = value_fn();
-			let needs_deep_read = false;
 			untrack(() => {
 				if (payload === undefined) {
 					payload = action(dom, value) || {};

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

@@ -1252,7 +1252,13 @@ export function pop(component) {
  * @returns {void}
  */
 export function deep_read(value, visited = new Set()) {
-	if (typeof value === 'object' && value !== null && !visited.has(value)) {
+	if (
+		typeof value === 'object' &&
+		value !== null &&
+		// We don't want to traverse DOM elements
+		!(value instanceof EventTarget) &&
+		!visited.has(value)
+	) {
 		visited.add(value);
 		for (let key in value) {
 			try {