fix: generate correct code for `each` blocks with async body (#16923)

* fix: generate correct code for `each` blocks with async body

* fix: else branch of `each` block

* chore: add expected html

.changeset/wicked-goats-begin.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: generate correct code for `each` blocks with async body

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

@@ -32,7 +32,9 @@ export function EachBlock(node, context) {
 		each.push(b.let(node.index, index));
 	}
 
-	each.push(.../** @type {BlockStatement} */ (context.visit(node.body)).body);
+	const new_body = /** @type {BlockStatement} */ (context.visit(node.body)).body;
+
+	each.push(...(node.body.metadata.has_await ? [create_async_block(b.block(new_body))] : new_body));
 
 	const for_loop = b.for(
 		b.declaration('let', [
@@ -55,7 +57,7 @@ export function EachBlock(node, context) {
 			b.if(
 				b.binary('!==', b.member(array_id, 'length'), b.literal(0)),
 				b.block([open, for_loop]),
-				fallback
+				node.fallback.metadata.has_await ? create_async_block(fallback) : fallback
 			)
 		);
 	} else {

packages/svelte/tests/server-side-rendering/samples/each-body-async/_config.js

@@ -0,0 +1,5 @@
+import { test } from '../../test';
+
+export default test({
+	mode: ['async']
+});

packages/svelte/tests/server-side-rendering/samples/each-body-async/_expected.html

@@ -0,0 +1 @@
+<!--[--><!--[--><!--[--><!---->each<!--]--><!--]--> <!--[--><!--[!--><!---->else<!--]--><!--]--><!--]-->

packages/svelte/tests/server-side-rendering/samples/each-body-async/main.svelte

@@ -0,0 +1,11 @@
+{#each { length: 1 }}
+	{@const data = await Promise.resolve("each")}
+	{data}
+{/each}
+
+{#each { length: 0 }}
+	should not see this
+{:else}
+	{@const data = await Promise.resolve("else")}
+	{data}
+{/each}