fix: preserve SSR context when block expressions contain await

Author: Rich-Harris

.changeset/friendly-months-prove.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: preserve SSR context when block expressions contain `await`

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

@@ -1,7 +1,6 @@
 /** @import { AwaitExpression, Expression } from 'estree' */
 /** @import { Context } from '../types' */
 import { save } from '../../../../utils/ast.js';
-import * as b from '../../../../utils/builders.js';
 
 /**
  * @param {AwaitExpression} node
@@ -14,5 +13,28 @@ export function AwaitExpression(node, context) {
 		return save(argument);
 	}
 
+	// we also need to restore context after block expressions
+	let i = context.path.length;
+	while (i--) {
+		const parent = context.path[i];
+
+		if (
+			parent.type === 'ArrowFunctionExpression' ||
+			parent.type === 'FunctionExpression' ||
+			parent.type === 'FunctionDeclaration'
+		) {
+			break;
+		}
+
+		// @ts-ignore
+		if (parent.metadata) {
+			if (parent.type !== 'ExpressionTag' && parent.type !== 'Fragment') {
+				return save(argument);
+			}
+
+			break;
+		}
+	}
+
 	return argument === node.argument ? node : { ...node, argument };
 }

packages/svelte/tests/runtime-runes/samples/async-push-element-dev/_config.js

@@ -0,0 +1,15 @@
+import { test } from '../../test';
+
+export default test({
+	mode: ['async-server'],
+
+	compileOptions: {
+		// include `push_element` calls, so that we can check they
+		// run with the correct ssr_context
+		dev: true
+	},
+
+	html: `
+		<h1>hello!</h1>
+	`
+});

packages/svelte/tests/runtime-runes/samples/async-push-element-dev/main.svelte

@@ -0,0 +1,3 @@
+{#if await true}
+	<h1>hello!</h1>
+{/if}

packages/svelte/tests/snapshot/samples/async-each-fallback-hoisting/_expected/server/index.svelte.js

@@ -3,7 +3,7 @@ import * as $ from 'svelte/internal/server';
 
 export default function Async_each_fallback_hoisting( $$renderer) {
 	 $$renderer.child(async ( $$renderer) => {
-		const each_array = $.ensure_array_like(await Promise.resolve([]));
+		const each_array = $.ensure_array_like((await $.save(Promise.resolve([])))());
 
 		if (each_array.length !== 0) {
 			 $$renderer.push('<!--[-->');

packages/svelte/tests/snapshot/samples/async-each-hoisting/_expected/server/index.svelte.js

@@ -9,7 +9,7 @@ export default function Async_each_hoisting( $$renderer) {
 	 $$renderer.push(`<!--[-->`);
 
 	 $$renderer.child(async ( $$renderer) => {
-		const each_array = $.ensure_array_like(await Promise.resolve([first, second, third]));
+		const each_array = $.ensure_array_like((await $.save(Promise.resolve([first, second, third])))());
 
 		for (let $$index = 0, $$length = each_array.length; $$index < $$length; $$index++) {
 			let item = each_array[$$index];

packages/svelte/tests/snapshot/samples/async-if-alternate-hoisting/_expected/server/index.svelte.js

@@ -3,7 +3,7 @@ import * as $ from 'svelte/internal/server';
 
 export default function Async_if_alternate_hoisting( $$renderer) {
 	 $$renderer.child(async ( $$renderer) => {
-		if (await Promise.resolve(false)) {
+		if ((await $.save(Promise.resolve(false)))()) {
 			 $$renderer.push('<!--[-->');
 			 $$renderer.push(async () => $.escape(await Promise.reject('no no no')));
 		} else {

packages/svelte/tests/snapshot/samples/async-if-hoisting/_expected/server/index.svelte.js

@@ -3,7 +3,7 @@ import * as $ from 'svelte/internal/server';
 
 export default function Async_if_hoisting( $$renderer) {
 	 $$renderer.child(async ( $$renderer) => {
-		if (await Promise.resolve(true)) {
+		if ((await $.save(Promise.resolve(true)))()) {
 			 $$renderer.push('<!--[-->');
 			 $$renderer.push(async () => $.escape(await Promise.resolve('yes yes yes')));
 		} else {