Merge 0f87bfaafc into 020242d6be

.changeset/calm-boundaries-wait.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: preserve reaction context for synchronous async expression errors

packages/svelte/src/internal/client/reactivity/deriveds.js

@@ -152,7 +152,8 @@ export function async_derived(fn, label, location) {
 				.finally(unset_context);
 		} catch (error) {
 			d.reject(error);
-			unset_context();
+			// Don't clear the reaction context before the current update has finished
+			queueMicrotask(unset_context);
 		}
 
 		if (DEV) {

packages/svelte/tests/runtime-runes/samples/async-boundary-sync-throw/_config.js

@@ -0,0 +1,18 @@
+import { tick } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	mode: ['client'],
+	compileOptions: {
+		dev: false
+	},
+
+	async test({ assert, target }) {
+		await tick();
+		assert.htmlEqual(target.innerHTML, '<button>invalidate</button><p>ready</p>');
+
+		target.querySelector('button')?.click();
+		await tick();
+		assert.htmlEqual(target.innerHTML, '<button>invalidate</button><p>original error</p>');
+	}
+});

packages/svelte/tests/runtime-runes/samples/async-boundary-sync-throw/main.svelte

@@ -0,0 +1,17 @@
+<script>
+	let valid = $state(true);
+
+	function load() {
+		if (!valid) throw new Error('original error');
+		return Promise.resolve('ready');
+	}
+</script>
+
+<button onclick={() => (valid = false)}>invalidate</button>
+
+<svelte:boundary>
+	<p>{await load()}</p>
+
+	{#snippet pending()}<p>pending</p>{/snippet}
+	{#snippet failed(error)}<p>{error.message}</p>{/snippet}
+</svelte:boundary>