fix: resolve remote modules as external during dev prebundling so packages can re-export remote functions

.changeset/remote-exports-prebundle.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+fix: resolve remote modules as external during dev prebundling so packages can re-export remote functions

packages/kit/src/exports/vite/index.js

@@ -12,6 +12,7 @@ import { exactRegex, prefixRegex } from 'rolldown/filter';
 
 import { copy, mkdirp, read, resolve_entry, rimraf } from '../../utils/filesystem.js';
 import { posixify } from '../../utils/os.js';
+import { to_fs } from '../../utils/vite.js';
 import {
 	create_sveltekit_env,
 	create_sveltekit_env_public,
@@ -472,22 +473,27 @@ function kit({ svelte_config }) {
 					}
 				};
 
-				// treat .remote.js files as empty for the purposes of prebundling
+				// externalize .remote.js files to stop dependency tracing during prebundling
 				if (kit.experimental.remoteFunctions) {
 					// @ts-expect-error optimizeDeps is already set above
 					new_config.optimizeDeps.rolldownOptions ??= {};
 					// @ts-expect-error
 					new_config.optimizeDeps.rolldownOptions.plugins ??= [];
 					// @ts-expect-error
-					new_config.optimizeDeps.rolldownOptions.plugins.push({
-						name: 'vite-plugin-sveltekit-setup:optimize-remote-functions',
-						load: {
-							filter: { id: remote_module_pattern },
-							handler() {
-								return '';
+					new_config.optimizeDeps.rolldownOptions.plugins.push(
+						/** @type {Rolldown.Plugin} */ ({
+							name: 'vite-plugin-sveltekit-setup:optimize-remote-functions',
+							resolveId: {
+								filter: { id: remote_module_pattern },
+								async handler(id, importer) {
+									const resolved = await this.resolve(id, importer, { skipSelf: true });
+									if (!resolved) return { id, external: true };
+									// a servable /@fs url; 'absolute' stops rolldown relativizing it in the deps bundle
+									return { id: to_fs(resolved.id), external: 'absolute' };
+								}
 							}
-						}
-					});
+						})
+					);
 				}
 
 				const define = {

packages/kit/test/apps/async/_test_dependencies/remote-lib/data.remote.js

@@ -0,0 +1,3 @@
+import { query } from '$app/server';
+
+export const lib_echo = query('unchecked', (value) => `lib says ${value}`);

packages/kit/test/apps/async/_test_dependencies/remote-lib/index.js

@@ -0,0 +1 @@
+export { lib_echo } from './data.remote.js';

packages/kit/test/apps/async/_test_dependencies/remote-lib/package.json

@@ -0,0 +1,8 @@
+{
+	"name": "e2e-test-dep-remote",
+	"version": "1.0.0",
+	"private": true,
+	"type": "module",
+	"main": "index.js",
+	"svelte": "./index.js"
+}

packages/kit/test/apps/async/package.json

@@ -21,7 +21,8 @@
 		"svelte-check": "catalog:",
 		"typescript": "catalog:",
 		"valibot": "catalog:",
-		"vite": "catalog:"
+		"vite": "catalog:",
+		"e2e-test-dep-remote": "file:./_test_dependencies/remote-lib"
 	},
 	"imports": {
 		"#lib": "./src/lib/index.js",

packages/kit/test/apps/async/src/routes/remote-lib/+page.svelte

@@ -0,0 +1,10 @@
+<script>
+	// @ts-ignore
+	import { lib_echo } from 'e2e-test-dep-remote';
+
+	let result = $state('');
+</script>
+
+<h1>{await lib_echo('hello')}</h1>
+<button onclick={async () => (result = await lib_echo('client'))}>call remote function</button>
+<p>{result}</p>

packages/kit/test/apps/async/test/client.test.js

@@ -30,6 +30,13 @@ test.describe('remote functions', () => {
 		const response = await response_promise;
 		expect(response.headers()['cache-control']).toBe('private, no-store');
 	});
+
+	test('packages can re-export remote functions', async ({ page }) => {
+		await page.goto('/remote-lib');
+		await expect(page.locator('h1')).toHaveText('lib says hello');
+		await page.getByRole('button', { name: 'call remote function' }).click();
+		await expect(page.locator('p')).toHaveText('lib says client');
+	});
 });
 
 // have to run in serial because commands mutate in-memory data on the server (should fix this at some point)