fix: set manifest and read implementation before evaluating remote function files during build (#14672)

* Initial plan

* Initial test setup for remote function read at top-level issue

Co-authored-by: teemingc <[email protected]>

* Update test to use prerender remote function

Co-authored-by: teemingc <[email protected]>

* Fix: set manifest and read implementation before loading remote functions in prerender

Co-authored-by: teemingc <[email protected]>

* Remove temporary test app

Co-authored-by: teemingc <[email protected]>

* Add page using with_read remote function and changeset

Co-authored-by: teemingc <[email protected]>

* Apply suggestion from @teemingc

* Apply suggestion from @teemingc

* Apply suggestion from @teemingc

* Apply suggestion from @teemingc

* Apply suggestion from @teemingc

* Apply suggestion from @teemingc

* Apply suggestion from @teemingc

---------

Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: teemingc <[email protected]>
Co-authored-by: Tee Ming <[email protected]>

Author: Copilot

.changeset/fix-remote-read-top-level.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+fix: allow `read` to be used at the top-level of remote function files

packages/kit/src/core/postbuild/analyse.js

@@ -56,7 +56,7 @@ async function analyse({
 	// essential we do this before analysing the code
 	internal.set_building();
 
-	// set env, in case it's used in initialisation
+	// set env, `read`, and `manifest`, in case they're used in initialisation
 	const { publicPrefix: public_prefix, privatePrefix: private_prefix } = config.env;
 	const private_env = filter_env(env, private_prefix, public_prefix);
 	const public_env = filter_env(env, public_prefix, private_prefix);

packages/kit/src/core/postbuild/prerender.js

@@ -485,14 +485,16 @@ async function prerender({ hash, out, manifest_path, metadata, verbose, env }) {
 		}
 	}
 
-	// the user's remote function modules may reference environment variables at
-	// the top-level so we need to set `env` before evaluating those modules
-	// to avoid potential runtime errors
+	// the user's remote function modules may reference environment variables,
+	// `read` or the `manifest` at the top-level so we need to set them before
+	// evaluating those modules to avoid potential runtime errors
 	const { publicPrefix: public_prefix, privatePrefix: private_prefix } = config.env;
 	const private_env = filter_env(env, private_prefix, public_prefix);
 	const public_env = filter_env(env, public_prefix, private_prefix);
 	internal.set_private_env(private_env);
 	internal.set_public_env(public_env);
+	internal.set_manifest(manifest);
+	internal.set_read_implementation((file) => createReadableStream(`${out}/server/${file}`));
 
 	/** @type {Array<import('types').RemoteInfo & { type: 'prerender'}>} */
 	const prerender_functions = [];

packages/kit/test/apps/basics/src/routes/remote/prerender/+page.svelte

@@ -1,8 +1,9 @@
 <script>
-	import { prerendered, prerendered_entries } from './prerender.remote.js';
+	import { prerendered, prerendered_entries, with_read } from './prerender.remote.js';
 
 	let prerendered_result = $state(null);
 	let live_result = $state(null);
+	let read_result = $state(null);
 </script>
 
 <a href="/remote/prerender/whole-page">whole-page</a>
@@ -17,3 +18,6 @@
 >
 	{live_result}
 </button>
+<button id="fetch-with-read" onclick={async () => (read_result = await with_read())}>
+	{read_result}
+</button>

packages/kit/test/apps/basics/src/routes/remote/prerender/prerender.remote.js

@@ -1,5 +1,11 @@
 import { building, dev } from '$app/environment';
-import { prerender } from '$app/server';
+import { prerender, read } from '$app/server';
+import text from './test.txt?url';
+
+// test that using `read()` at the top-level of a remote function file doesn't
+// throw an error when we evaluate the remote function files during build
+const response = read(text);
+const content = await response.text();
 
 export const prerendered = prerender(() => {
 	if (!building && !dev) {
@@ -23,3 +29,7 @@ export const prerendered_entries = prerender(
 	},
 	{ inputs: () => ['a', 'b', /* to test correct encoding */ '中文'], dynamic: true }
 );
+
+export const with_read = prerender(() => {
+	return content;
+});

packages/kit/test/apps/basics/src/routes/remote/prerender/test.txt

@@ -0,0 +1 @@
+test content from read()