abort synchronously in SSR

packages/svelte/src/index-server.js

@@ -2,7 +2,6 @@
 import { current_component } from './internal/server/context.js';
 import { noop } from './internal/shared/utils.js';
 import * as e from './internal/server/errors.js';
-import { STALE_REACTION } from '#client/constants';
 
 /** @param {() => void} fn */
 export function onDestroy(fn) {
@@ -36,20 +35,7 @@ export function unmount() {
 
 export async function tick() {}
 
-/** @type {AbortController | null} */
+export { getAbortSignal } from './internal/server/abort-signal.js';
-let controller = null;
-
-export function getAbortSignal() {
-	if (controller === null) {
-		const c = (controller = new AbortController());
-		queueMicrotask(() => {
-			c.abort(STALE_REACTION);
-			controller = null;
-		});
-	}
-
-	return controller.signal;
-}
 
 export { getAllContexts, getContext, hasContext, setContext } from './internal/server/context.js';
 

packages/svelte/src/internal/server/abort-signal.js

@@ -0,0 +1,15 @@
+import { STALE_REACTION } from '#client/constants';
+
+/** @type {AbortController | null} */
+export let controller = null;
+
+export function abort() {
+	if (controller !== null) {
+		controller.abort(STALE_REACTION);
+		controller = null;
+	}
+}
+
+export function getAbortSignal() {
+	return (controller ??= new AbortController()).signal;
+}

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

@@ -18,6 +18,7 @@ import { validate_store } from '../shared/validate.js';
 import { is_boolean_attribute, is_raw_text_element, is_void } from '../../utils.js';
 import { reset_elements } from './dev.js';
 import { Payload } from './payload.js';
+import { abort } from './abort-signal.js';
 
 // https://html.spec.whatwg.org/multipage/syntax.html#attributes-2
 // https://infra.spec.whatwg.org/#noncharacter
@@ -66,6 +67,7 @@ export let on_destroy = [];
  * @returns {RenderOutput}
  */
 export function render(component, options = {}) {
+	try {
 		const payload = new Payload(options.idPrefix ? options.idPrefix + '-' : '');
 
 		const prev_on_destroy = on_destroy;
@@ -110,6 +112,9 @@ export function render(component, options = {}) {
 			html: payload.out,
 			body: payload.out
 		};
+	} finally {
+		abort();
+	}
 }
 
 /**