fix: improve indexed each equality (#10702)

Author: trueadm

.changeset/spotty-houses-search.md

@@ -0,0 +1,5 @@
+---
+"svelte": patch
+---
+
+fix: improve indexed each equality

packages/svelte/src/internal/client/dom/blocks/each.js

@@ -332,6 +332,11 @@ function reconcile_indexed_array(
 	flags,
 	apply_transitions
 ) {
+	// If we are working with an array that isn't proxied or frozen, then remove strict equality and ensure the items
+	// are treated as reactive, so they get wrapped in a signal.
+	if ((flags & EACH_IS_STRICT_EQUALS) !== 0 && !is_frozen(array) && !(STATE_SYMBOL in array)) {
+		flags ^= EACH_IS_STRICT_EQUALS;
+	}
 	var a_blocks = each_block.v;
 	var active_transitions = each_block.s;
 
@@ -449,7 +454,8 @@ function reconcile_tracked_array(
 	apply_transitions,
 	keys
 ) {
-	// If we are working with an array that isn't proxied or frozen, then remove strict equality.
+	// If we are working with an array that isn't proxied or frozen, then remove strict equality and ensure the items
+	// are treated as reactive, so they get wrapped in a signal.
 	if ((flags & EACH_IS_STRICT_EQUALS) !== 0 && !is_frozen(array) && !(STATE_SYMBOL in array)) {
 		flags ^= EACH_IS_STRICT_EQUALS;
 	}

packages/svelte/tests/runtime-runes/samples/each-updates-5/_config.js

@@ -0,0 +1,21 @@
+import { flushSync } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	html: `1\n1\n<button>+</button>`,
+
+	async test({ assert, target }) {
+		/**
+		 * @type {{ click: () => void; }}
+		 */
+		let btn1;
+
+		[btn1] = target.querySelectorAll('button');
+
+		flushSync(() => {
+			btn1.click();
+		});
+
+		assert.htmlEqual(target.innerHTML, `2\n2\n<button>+</button>`);
+	}
+});

packages/svelte/tests/runtime-runes/samples/each-updates-5/main.svelte

@@ -0,0 +1,20 @@
+<script>
+	import { writable } from "svelte/store";
+
+	let store = writable([{ value: 1 }]);
+	let storeDeeper = writable({ items: [{ value: 1 }] });
+
+	function increment() {
+		$store[0].value++;
+		$storeDeeper.items[0].value++;
+	}
+</script>
+
+{#each $store as item}
+	{item.value}
+{/each}
+{#each $storeDeeper.items as item}
+	{item.value}
+{/each}
+
+<button onclick={increment}>+</button>