fix: optimize bind:group (#12406)

Author: Rich-Harris

.changeset/wicked-bikes-matter.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: optimize `bind:group`

packages/svelte/src/internal/client/dom/elements/bindings/input.js

@@ -53,8 +53,11 @@ export function bind_value(input, get_value, update) {
 	});
 }
 
+/** @type {Set<HTMLInputElement[]>} */
+const pending = new Set();
+
 /**
- * @param {Array<HTMLInputElement>} inputs
+ * @param {HTMLInputElement[]} inputs
  * @param {null | [number]} group_index
  * @param {HTMLInputElement} input
  * @param {() => unknown} get_value
@@ -127,10 +130,17 @@ export function bind_group(inputs, group_index, input, get_value, update) {
 		}
 	});
 
-	queue_micro_task(() => {
-		// necessary to maintain binding group order in all insertion scenarios. TODO optimise
-		binding_group.sort((a, b) => (a.compareDocumentPosition(b) === 4 ? -1 : 1));
+	if (!pending.has(binding_group)) {
+		pending.add(binding_group);
 
+		queue_micro_task(() => {
+			// necessary to maintain binding group order in all insertion scenarios
+			binding_group.sort((a, b) => (a.compareDocumentPosition(b) === 4 ? -1 : 1));
+			pending.delete(binding_group);
+		});
+	}
+
+	queue_micro_task(() => {
 		if (hydration_mismatch) {
 			var value;