fix: generate edge middleware to run reroute

.changeset/hot-guests-enjoy.md

@@ -0,0 +1,6 @@
+---
+"@sveltejs/adapter-netlify": minor
+"@sveltejs/adapter-vercel": minor
+---
+
+fix: run `reroute` in an edge middleware if the app has been split into multiple functions

documentation/docs/25-build-and-deploy/80-adapter-netlify.md

@@ -107,6 +107,12 @@ Additionally, you can add your own Netlify functions by creating a directory for
 	directory = "functions"
 ```
 
+## Notes
+
+### Individual functions and `reroute`
+
+If the `split` option is set to `true` in the adapter config, the [`reroute`](/docs/hooks#universal-hooks-reroute) function will be deployed as an edge middleware that runs before any individual function.
+
 ## Troubleshooting
 
 ### Accessing the file system

documentation/docs/25-build-and-deploy/90-adapter-vercel.md

@@ -189,6 +189,10 @@ If you have Vercel functions contained in the `api` directory at the project's r
 
 Projects created before a certain date may default to using an older Node version than what SvelteKit currently requires. You can [change the Node version in your project settings](https://vercel.com/docs/concepts/functions/serverless-functions/runtimes/node-js#node.js-version).
 
+### Individual functions and `reroute`
+
+If the `split` option is set to `true` for a route, or at the adapter level, the [`reroute`](/docs/hooks#universal-hooks-reroute) function will be deployed as an edge middleware that runs before any individual function.
+
 ## Troubleshooting
 
 ### Accessing the file system

packages/adapter-netlify/index.js

@@ -98,6 +98,13 @@ export default function ({ split = false, edge = edge_set_in_env_var } = {}) {
 				await generate_edge_functions({ builder });
 			} else {
 				generate_lambda_functions({ builder, split, publish });
+
+				/** @type {string | void} */
+				let reroute_path;
+
+				if (split && (reroute_path = await builder.getReroutePath())) {
+					await generate_reroute_middleware({ builder, reroute_path });
+				}
 			}
 		},
 
@@ -115,6 +122,7 @@ export default function ({ split = false, edge = edge_set_in_env_var } = {}) {
 		}
 	};
 }
+
 /**
  * @param { object } params
  * @param {import('@sveltejs/kit').Builder} params.builder
@@ -127,6 +135,7 @@ async function generate_edge_functions({ builder }) {
 	builder.mkdirp('.netlify/edge-functions');
 
 	builder.log.minor('Generating Edge Function...');
+
 	const relativePath = posix.relative(tmp, builder.getServerDirectory());
 
 	builder.copy(`${files}/edge.js`, `${tmp}/entry.js`, {
@@ -136,12 +145,67 @@ async function generate_edge_functions({ builder }) {
 		}
 	});
 
-	const manifest = builder.generateManifest({
-		relativePath
+	await bundle_edge_function({ builder, name: 'render' });
+}
+
+/**
+ * @param {object} params
+ * @param {import('@sveltejs/kit').Builder} params.builder
+ * @param {string} params.reroute_path
+ */
+async function generate_reroute_middleware({ builder, reroute_path }) {
+	const tmp = builder.getBuildDirectory('netlify-tmp');
+	builder.rimraf(tmp);
+	builder.mkdirp(tmp);
+
+	builder.mkdirp('.netlify/edge-functions');
+
+	builder.log.minor('Generating Reroute Edge Function...');
+
+	builder.copy(`${files}/reroute.js`, `${tmp}/entry.js`, {
+		replace: {
+			__HOOKS__: reroute_path
+		}
 	});
 
+	await bundle_edge_function({ builder, name: 'reroute' });
+}
+
+/**
+ *
+ * @param {object} params
+ * @param {import('@sveltejs/kit').Builder} params.builder
+ * @param {string} params.name
+ */
+async function bundle_edge_function({ builder, name }) {
+	const tmp = builder.getBuildDirectory('netlify-tmp');
+
+	const relativePath = posix.relative(tmp, builder.getServerDirectory());
+	const manifest = builder.generateManifest({ relativePath });
 	writeFileSync(`${tmp}/manifest.js`, `export const manifest = ${manifest};\n`);
 
+	await esbuild.build({
+		entryPoints: [`${tmp}/entry.js`],
+		outfile: `.netlify/edge-functions/${name}.js`,
+		bundle: true,
+		format: 'esm',
+		platform: 'browser',
+		sourcemap: 'linked',
+		target: 'es2020',
+		loader: {
+			'.wasm': 'copy',
+			'.woff': 'copy',
+			'.woff2': 'copy',
+			'.ttf': 'copy',
+			'.eot': 'copy',
+			'.otf': 'copy'
+		},
+		// Node built-ins are allowed, but must be prefixed with `node:`
+		// https://docs.netlify.com/edge-functions/api/#runtime-environment
+		external: builtinModules.map((id) => `node:${id}`),
+		alias: Object.fromEntries(builtinModules.map((id) => [id, `node:${id}`]))
+	});
+
 	/** @type {{ assets: Set<string> }} */
 	const { assets } = (await import(`${tmp}/manifest.js`)).manifest;
 
@@ -170,38 +234,17 @@ async function generate_edge_functions({ builder }) {
 	const edge_manifest = {
 		functions: [
 			{
-				function: 'render',
+				function: name,
 				path,
 				excludedPath
 			}
 		],
 		version: 1
 	};
 
-	await esbuild.build({
-		entryPoints: [`${tmp}/entry.js`],
-		outfile: '.netlify/edge-functions/render.js',
-		bundle: true,
-		format: 'esm',
-		platform: 'browser',
-		sourcemap: 'linked',
-		target: 'es2020',
-		loader: {
-			'.wasm': 'copy',
-			'.woff': 'copy',
-			'.woff2': 'copy',
-			'.ttf': 'copy',
-			'.eot': 'copy',
-			'.otf': 'copy'
-		},
-		// Node built-ins are allowed, but must be prefixed with `node:`
-		// https://docs.netlify.com/edge-functions/api/#runtime-environment
-		external: builtinModules.map((id) => `node:${id}`),
-		alias: Object.fromEntries(builtinModules.map((id) => [id, `node:${id}`]))
-	});
-
 	writeFileSync('.netlify/edge-functions/manifest.json', JSON.stringify(edge_manifest));
 }
+
 /**
  * @param { object } params
  * @param {import('@sveltejs/kit').Builder} params.builder

packages/adapter-netlify/internal.d.ts

@@ -7,3 +7,10 @@ declare module 'MANIFEST' {
 
 	export const manifest: SSRManifest;
 }
+
+declare module '__HOOKS__' {
+	// eslint-disable-next-line no-duplicate-imports
+	import { Reroute } from '@sveltejs/kit';
+
+	export const reroute: Reroute;
+}

packages/adapter-netlify/package.json

@@ -59,6 +59,6 @@
 		"vitest": "^3.0.1"
 	},
 	"peerDependencies": {
-		"@sveltejs/kit": "^2.4.0"
+		"@sveltejs/kit": "^2.17.0"
 	}
 }

packages/adapter-netlify/rollup.config.js

@@ -2,20 +2,32 @@ import { nodeResolve } from '@rollup/plugin-node-resolve';
 import commonjs from '@rollup/plugin-commonjs';
 import json from '@rollup/plugin-json';
 
-/** @type {import('rollup').RollupOptions} */
-const config = {
-	input: {
-		serverless: 'src/serverless.js',
-		shims: 'src/shims.js'
+/** @type {import('rollup').RollupOptions[]} */
+const config = [
+	{
+		input: {
+			serverless: 'src/serverless.js',
+			shims: 'src/shims.js'
+		},
+		output: {
+			dir: 'files/esm',
+			format: 'esm'
+		},
+		// @ts-ignore https://github.com/rollup/plugins/issues/1329
+		plugins: [nodeResolve({ preferBuiltins: true }), commonjs(), json()],
+		external: (id) => id === '0SERVER' || id.startsWith('node:'),
+		preserveEntrySignatures: 'exports-only'
 	},
-	output: {
-		dir: 'files/esm',
-		format: 'esm'
-	},
-	// @ts-ignore https://github.com/rollup/plugins/issues/1329
-	plugins: [nodeResolve({ preferBuiltins: true }), commonjs(), json()],
-	external: (id) => id === '0SERVER' || id.startsWith('node:'),
-	preserveEntrySignatures: 'exports-only'
-};
+	{
+		input: 'src/reroute.js',
+		output: {
+			file: 'files/reroute.js',
+			format: 'esm'
+		},
+		plugins: [nodeResolve({ preferBuiltins: true })],
+		external: (id) => id === '__HOOKS__',
+		preserveEntrySignatures: 'exports-only'
+	}
+];
 
 export default config;

packages/adapter-netlify/src/reroute.js

@@ -0,0 +1,18 @@
+import { reroute } from '__HOOKS__';
+import { applyReroute } from '@sveltejs/kit/adapter';
+
+/**
+ * @param {Request} request
+ * @returns {URL | undefined}
+ */
+export default function middleware(request) {
+	const url = new URL(request.url);
+	const rerouted_path = applyReroute(url, reroute);
+
+	// a rewrite on Netlify will cause this function to run again with the new URL
+	// instead of moving onto the route function, so we only return a URL if
+	// the reroute path is different from the original to avoid an endless loop
+	if (rerouted_path && url.pathname !== rerouted_path.pathname) {
+		return rerouted_path;
+	}
+}

packages/adapter-vercel/.gitignore

@@ -1,2 +1,3 @@
 .DS_Store
 node_modules
+/files