fix: generate edge middleware to run reroute

.changeset/hot-guests-enjoy.md

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

.changeset/modern-dogs-tie.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': minor
+---
+
+feat: add `applyReroute` and `builder.getReroutePath` helpers for running `reroute` in a middleware before the main handler

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

@@ -120,6 +120,12 @@ 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`](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`](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/98-reference/15-@sveltejs-kit-adapter.md

@@ -0,0 +1,5 @@
+---
+title:  @sveltejs/kit/adapter
+---
+
+> MODULE: @sveltejs/kit/adapter

eslint.config.js

@@ -52,6 +52,7 @@ export default [
 		},
 		ignores: [
 			'packages/adapter-cloudflare/test/apps/**/*',
+			'packages/adapter-netlify/test/preview.js',
 			'packages/adapter-netlify/test/apps/**/*',
 			'packages/adapter-node/rollup.config.js',
 			'packages/adapter-node/tests/smoke.spec_disabled.js',
@@ -60,8 +61,7 @@ export default [
 			'packages/kit/test/apps/**/*',
 			'packages/kit/test/build-errors/**/*',
 			'packages/kit/test/prerendering/**/*',
-			'packages/test-redirect-importer/index.js',
-			'packages/adapter-netlify/test/preview.js'
+			'packages/test-redirect-importer/index.js'
 		]
 	}
 ];

package.json

@@ -45,7 +45,6 @@
 			"rolldown",
 			"sharp",
 			"svelte-preprocess",
-			"unix-dgram",
 			"workerd"
 		]
 	}

packages/adapter-netlify/index.js

@@ -97,14 +97,24 @@ export default function ({ split = false, edge = edge_set_in_env_var } = {}) {
 				`\n\n/${builder.getAppPath()}/immutable/*\n  cache-control: public\n  cache-control: immutable\n  cache-control: max-age=31536000\n`
 			);
 
+			let reroute_middleware = false;
+
 			if (edge) {
 				if (split) {
 					throw new Error('Cannot use `split: true` alongside `edge: true`');
 				}
 
-				await generate_edge_functions({ builder });
+				await generate_edge_functions({ builder, reroute_middleware });
 			} 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 });
+					reroute_middleware = true;
+				}
+
+				generate_lambda_functions({ builder, split, publish, reroute_middleware });
 			}
 		},
 
@@ -123,18 +133,21 @@ export default function ({ split = false, edge = edge_set_in_env_var } = {}) {
 		}
 	};
 }
+
 /**
- * @param { object } params
+ * @param {object} params
  * @param {Builder2_4_0} params.builder
+ * @param {boolean} params.reroute_middleware
  */
-async function generate_edge_functions({ builder }) {
+async function generate_edge_functions({ builder, reroute_middleware }) {
 	const tmp = builder.getBuildDirectory('netlify-tmp');
 	builder.rimraf(tmp);
 	builder.mkdirp(tmp);
 
 	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`, {
@@ -144,49 +157,48 @@ async function generate_edge_functions({ builder }) {
 		}
 	});
 
-	const manifest = builder.generateManifest({
-		relativePath
-	});
+	await bundle_edge_function({ builder, name: 'render', reroute_middleware });
+}
 
-	writeFileSync(`${tmp}/manifest.js`, `export const manifest = ${manifest};\n`);
+/**
+ * @param {object} params
+ * @param {Builder2_4_0} params.builder
+ * @param {string} params.reroute_path
+ */
+async function generate_reroute_middleware({ builder, reroute_path }) {
+	builder.log.minor('Generating edge middleware to run reroute before split functions...');
 
-	/** @type {{ assets: Set<string> }} */
-	// we have to prepend the file:// protocol because Windows doesn't support absolute path imports
-	const { assets } = (await import(`file://${tmp}/manifest.js`)).manifest;
+	const tmp = builder.getBuildDirectory('netlify-tmp');
+	builder.rimraf(tmp);
+	builder.mkdirp(tmp);
 
-	const path = '/*';
-	// We only need to specify paths without the trailing slash because
-	// Netlify will handle the optional trailing slash for us
-	const excluded = [
-		// Contains static files
-		`/${builder.getAppPath()}/immutable/*`,
-		`/${builder.getAppPath()}/version.json`,
-		...builder.prerendered.paths,
-		...Array.from(assets).flatMap((asset) => {
-			if (asset.endsWith('/index.html')) {
-				const dir = asset.replace(/\/index\.html$/, '');
-				return [
-					`${builder.config.kit.paths.base}/${asset}`,
-					`${builder.config.kit.paths.base}/${dir}`
-				];
-			}
-			return `${builder.config.kit.paths.base}/${asset}`;
-		}),
-		// Should not be served by SvelteKit at all
-		'/.netlify/*'
-	];
+	builder.mkdirp('.netlify/edge-functions');
 
-	/** @type {import('@netlify/edge-functions').Manifest} */
-	const edge_manifest = {
-		functions: [
-			{
-				function: 'render',
-				path,
-				excludedPath: /** @type {`/${string}`[]} */ (excluded)
-			}
-		],
-		version: 1
-	};
+	builder.copy(`${files}/reroute.js`, `${tmp}/entry.js`, {
+		replace: {
+			__HOOKS__: reroute_path
+		}
+	});
+
+	await bundle_edge_function({ builder, name: 'reroute', reroute_middleware: false });
+}
+
+/**
+ *
+ * @param {object} params
+ * @param {Builder2_4_0} params.builder
+ * @param {string} params.name
+ * @param {boolean} params.reroute_middleware
+ */
+async function bundle_edge_function({ builder, name, reroute_middleware }) {
+	const tmp = builder.getBuildDirectory('netlify-tmp');
+
+	const relativePath = posix.relative(tmp, builder.getServerDirectory());
+	const manifest = builder.generateManifest({
+		relativePath,
+		rerouteMiddleware: reroute_middleware
+	});
+	writeFileSync(`${tmp}/manifest.js`, `export const manifest = ${manifest};\n`);
 
 	/** @type {BuildOptions} */
 	const esbuild_config = {
@@ -211,7 +223,7 @@ async function generate_edge_functions({ builder }) {
 	await Promise.all([
 		esbuild.build({
 			entryPoints: [`${tmp}/entry.js`],
-			outfile: '.netlify/edge-functions/render.js',
+			outfile: `.netlify/edge-functions/${name}.js`,
 			...esbuild_config
 		}),
 		builder.hasServerInstrumentationFile?.() &&
@@ -230,15 +242,55 @@ async function generate_edge_functions({ builder }) {
 		});
 	}
 
+	/** @type {{ assets: Set<string> }} */
+	// we have to prepend the file:// protocol because Windows doesn't support absolute path imports
+	const { assets } = (await import(`file://${tmp}/manifest.js`)).manifest;
+
+	// We only need to specify paths without the trailing slash because
+	// Netlify will handle the optional trailing slash for us
+	const app_path = builder.getAppPath();
+	const excluded = [
+		// Contains static files
+		`/${app_path}/immutable/*`,
+		`/${app_path}/version.json`,
+		...builder.prerendered.paths,
+		...Array.from(assets).flatMap((asset) => {
+			if (asset.endsWith('/index.html')) {
+				const dir = asset.replace(/\/index\.html$/, '');
+				return [
+					`${builder.config.kit.paths.base}/${asset}`,
+					`${builder.config.kit.paths.base}/${dir}`
+				];
+			}
+			return `${builder.config.kit.paths.base}/${asset}`;
+		}),
+		// Should not be served by SvelteKit at all
+		'/.netlify/*'
+	];
+
+	/** @type {import('@netlify/edge-functions').Manifest} */
+	const edge_manifest = {
+		functions: [
+			{
+				function: name,
+				path: '/*',
+				excludedPath: /** @type {`/${string}`[]} */ (excluded)
+			}
+		],
+		version: 1
+	};
+
 	writeFileSync('.netlify/edge-functions/manifest.json', JSON.stringify(edge_manifest));
 }
+
 /**
- * @param { object } params
+ * @param {object} params
  * @param {Builder2_4_0} params.builder
- * @param { string } params.publish
- * @param { boolean } params.split
+ * @param {string} params.publish
+ * @param {boolean} params.split
+ * @param {boolean} params.reroute_middleware
  */
-function generate_lambda_functions({ builder, publish, split }) {
+function generate_lambda_functions({ builder, publish, split, reroute_middleware }) {
 	builder.mkdirp('.netlify/functions-internal/.svelte-kit');
 
 	/** @type {string[]} */
@@ -299,7 +351,8 @@ function generate_lambda_functions({ builder, publish, split }) {
 
 			const manifest = builder.generateManifest({
 				relativePath: '../server',
-				routes
+				routes,
+				rerouteMiddleware: reroute_middleware
 			});
 
 			const fn = `import { init } from '../serverless.js';\n\nexport const handler = init(${manifest});\n`;
@@ -323,7 +376,8 @@ function generate_lambda_functions({ builder, publish, split }) {
 		}
 	} else {
 		const manifest = builder.generateManifest({
-			relativePath: '../server'
+			relativePath: '../server',
+			rerouteMiddleware: reroute_middleware
 		});
 
 		const fn = `import { init } from '../serverless.js';\n\nexport const handler = init(${manifest});\n`;

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

@@ -60,11 +60,11 @@
 		"@sveltejs/vite-plugin-svelte": "catalog:",
 		"@types/node": "catalog:",
 		"@types/set-cookie-parser": "catalog:",
-		"rollup": "^4.14.2",
+		"rollup": "catalog:",
 		"typescript": "^5.3.3",
 		"vitest": "catalog:"
 	},
 	"peerDependencies": {
-		"@sveltejs/kit": "^2.4.0"
+		"@sveltejs/kit": "^2.51.0"
 	}
 }

packages/adapter-netlify/rollup.config.js

@@ -3,6 +3,8 @@ import commonjs from '@rollup/plugin-commonjs';
 import json from '@rollup/plugin-json';
 import { rmSync } from 'node:fs';
 
+const EXTERNAL = new Set(['0SERVER', 'MANIFEST', '__HOOKS__']);
+
 /**
  * @param {string} filepath
  * @returns {import('rollup').Plugin}
@@ -25,15 +27,16 @@ const config = {
 	input: {
 		serverless: 'src/serverless.js',
 		shims: 'src/shims.js',
-		edge: 'src/edge.js'
+		edge: 'src/edge.js',
+		reroute: 'src/reroute.js'
 	},
 	output: {
 		dir: 'files',
 		format: 'esm'
 	},
 	// @ts-ignore https://github.com/rollup/plugins/issues/1329
 	plugins: [clearOutput('files'), nodeResolve({ preferBuiltins: true }), commonjs(), json()],
-	external: (id) => id === '0SERVER' || id === 'MANIFEST' || id.startsWith('node:'),
+	external: (id) => EXTERNAL.has(id) || id.startsWith('node:'),
 	preserveEntrySignatures: 'exports-only'
 };
 

packages/adapter-netlify/src/reroute.js

@@ -0,0 +1,13 @@
+import { reroute } from '__HOOKS__';
+import { applyReroute } from '@sveltejs/kit/adapter';
+
+/** @type {import('@netlify/edge-functions').EdgeFunction} */
+export default async function middleware(request, context) {
+	const resolved_url = await applyReroute(request.url, reroute);
+
+	// Netlify rewrites can cause an endless loop because it will re-run this
+	// function with the rewritten URL. Therefore, we use `context.next` instead
+	// to specifically invoke the next function in the chain with the rewritten URL
+	const new_request = new Request(resolved_url, request);
+	return context.next(new_request);
+}

packages/adapter-netlify/src/serverless.js

@@ -57,7 +57,7 @@ export function init(manifest) {
  * @param {import('@netlify/functions').HandlerEvent} event
  * @returns {Request}
  */
-function to_request({ httpMethod, headers, rawUrl, body, isBase64Encoded }) {
+function to_request({ httpMethod, headers, rawUrl, rawQuery, body, isBase64Encoded }) {
 	/** @type {RequestInit} */
 	const init = {
 		method: httpMethod,
@@ -69,7 +69,7 @@ function to_request({ httpMethod, headers, rawUrl, body, isBase64Encoded }) {
 		init.body = typeof body === 'string' ? Buffer.from(body, encoding) : body;
 	}
 
-	return new Request(rawUrl, init);
+	return new Request(rawUrl + (rawQuery ? `?${rawQuery}` : ''), init);
 }
 
 const text_types = new Set([

packages/adapter-netlify/test/apps/basic/netlify.toml

@@ -1,2 +1,2 @@
-[dev]
+[build]
 publish = "build"

packages/adapter-netlify/test/apps/basic/netlify/functions/render.mjs

@@ -35,5 +35,6 @@ export default async function (request, context) {
 }
 
 export const config = {
-	path: '/*'
+	path: '/*',
+	preferStatic: true
 };