WIP

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

@@ -41,7 +41,7 @@ import { TitleElement } from './visitors/TitleElement.js';
 import { UpdateExpression } from './visitors/UpdateExpression.js';
 import { VariableDeclaration } from './visitors/VariableDeclaration.js';
 import { SvelteBoundary } from './visitors/SvelteBoundary.js';
-import { call_component_renderer, create_async_block } from './visitors/shared/utils.js';
+import { call_component_renderer } from './visitors/shared/utils.js';
 
 /** @type {Visitors} */
 const global_visitors = {

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

@@ -323,8 +323,12 @@ export function build_inline_component(node, expression, context) {
 		);
 	}
 
-	if (optimiser.expressions.length > 0) {
-		statement = create_async_block(b.block([optimiser.apply(), statement]));
+	if (optimiser.is_async()) {
+		statement = create_async_block(
+			b.block([optimiser.apply(), statement]),
+			optimiser.blockers(),
+			optimiser.has_await
+		);
 	}
 
 	if (dynamic && custom_css_props.length === 0) {

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

@@ -1,5 +1,5 @@
 /** @import { Expression, Identifier, Node, Statement, BlockStatement, ArrayExpression } from 'estree' */
-/** @import { AST } from '#compiler' */
+/** @import { AST, Binding } from '#compiler' */
 /** @import { ComponentContext, ServerTransformState } from '../../types.js' */
 
 import { escape_html } from '../../../../../../escaping.js';
@@ -299,13 +299,26 @@ export class PromiseOptimiser {
 	/** @type {Expression[]} */
 	expressions = [];
 
+	has_await = false;
+
+	/** @type {Set<Expression>} */
+	#blockers = new Set();
+
 	/**
 	 *
 	 * @param {Expression} expression
 	 * @param {ExpressionMetadata} metadata
 	 */
 	transform = (expression, metadata) => {
+		for (const binding of metadata.dependencies) {
+			if (binding.blocker) {
+				this.#blockers.add(binding.blocker);
+			}
+		}
+
 		if (metadata.has_await) {
+			this.has_await = true;
+
 			const length = this.expressions.push(expression);
 			return b.id(`$$${length - 1}`);
 		}
@@ -314,6 +327,10 @@ export class PromiseOptimiser {
 	};
 
 	apply() {
+		if (this.expressions.length === 0) {
+			return b.empty;
+		}
+
 		if (this.expressions.length === 1) {
 			return b.const('$$0', this.expressions[0]);
 		}
@@ -331,4 +348,12 @@ export class PromiseOptimiser {
 			b.await(b.call('Promise.all', promises))
 		);
 	}
+
+	blockers() {
+		return b.array([...this.#blockers]);
+	}
+
+	is_async() {
+		return this.expressions.length > 0 || this.#blockers.size > 0;
+	}
 }

packages/svelte/src/internal/server/renderer.js

@@ -148,6 +148,8 @@ export class Renderer {
 					set_ssr_context(previous_context);
 				}
 			});
+
+			promises.push(promise);
 		}
 
 		return promises;