fix: detect store in each block expression regardless of AST shape (#17636)

The store invalidation detection in each blocks only checked for
Identifier and MemberExpression AST node types. This caused bind:
on iteration variables to silently fail when the expression used
logical operators (e.g. `{#each $store.items ?? [] as item}`).

Use expression metadata dependencies instead of AST type checking
to find store_sub bindings, which correctly handles all expression
shapes.

Fixes #14625

.changeset/fix-each-bind-store-logical.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: detect store in each block expression regardless of AST shape

packages/svelte/src/compiler/phases/3-transform/client/visitors/EachBlock.js

@@ -101,15 +101,11 @@ export function EachBlock(node, context) {
 	}
 
 	// If the array is a store expression, we need to invalidate it when the array is changed.
-	// This doesn't catch all cases, but all the ones that Svelte 4 catches, too.
 	let store_to_invalidate = '';
-	if (node.expression.type === 'Identifier' || node.expression.type === 'MemberExpression') {
+	for (const binding of node.metadata.expression.dependencies) {
-		const id = object(node.expression);
+		if (binding.kind === 'store_sub') {
-		if (id) {
+			store_to_invalidate = binding.node.name;
-			const binding = context.state.scope.get(id.name);
+			break;
-			if (binding?.kind === 'store_sub') {
-				store_to_invalidate = id.name;
-			}
 		}
 	}
 

packages/svelte/tests/runtime-legacy/samples/store-each-binding-logical/_config.js

@@ -0,0 +1,22 @@
+import { flushSync } from 'svelte';
+import { ok, test } from '../../test';
+
+export default test({
+	test({ assert, target, window }) {
+		const input = target.querySelector('input');
+		ok(input);
+
+		const event = new window.Event('input');
+		input.value = 'changed';
+		input.dispatchEvent(event);
+		flushSync();
+
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			<input>
+			<p>changed</p>
+		`
+		);
+	}
+});

packages/svelte/tests/runtime-legacy/samples/store-each-binding-logical/main.svelte

@@ -0,0 +1,13 @@
+<script>
+	import { writable } from 'svelte/store';
+
+	const items = writable([
+		{ id: 0, text: 'initial' }
+	]);
+</script>
+
+{#each $items ?? [] as item}
+	<input bind:value={item.text}>
+{/each}
+
+<p>{$items[0].text}</p>