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

.prettierrc

@@ -26,6 +26,8 @@
 				"**/.custom-out-dir/**",
 				"**/build/**",
 				"**/test-results/**",
+				"**/.netlify/**",
+				"**/dist/**",
 				"documentation/**/*.md",
 				"packages/package/test/fixtures/**/expected/**/*",
 				"packages/package/test/watch/expected/**/*",

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

@@ -111,6 +111,12 @@ 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

@@ -188,6 +188,10 @@ 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

eslint.config.js

@@ -14,6 +14,9 @@ export default [
 			'**/test-results',
 			'**/build',
 			'**/.custom-out-dir',
+			'**/.wrangler',
+			'**/.netlify',
+			'**/dist',
 			'packages/adapter-*/files'
 		]
 	},
@@ -31,9 +34,12 @@ export default [
 		},
 		ignores: [
 			'packages/adapter-cloudflare/test/apps/**/*',
+			'packages/adapter-netlify/test/apps/**/*',
+			'packages/adapter-netlify/rollup.config.js',
 			'packages/adapter-node/rollup.config.js',
 			'packages/adapter-node/tests/smoke.spec_disabled.js',
 			'packages/adapter-static/test/apps/**/*',
+			'packages/adapter-vercel/rollup.config.js',
 			'packages/create-svelte/shared/**/*',
 			'packages/create-svelte/templates/**/*',
 			'packages/kit/src/core/sync/create_manifest_data/test/samples/**/*',

package.json

@@ -37,8 +37,11 @@
 	},
 	"pnpm": {
 		"onlyBuiltDependencies": [
+			"@parcel/watcher",
 			"esbuild",
+			"netlify-cli",
 			"sharp",
+			"unix-dgram",
 			"svelte-preprocess",
 			"workerd"
 		]

packages/adapter-netlify/index.js

@@ -13,26 +13,6 @@ import toml from '@iarna/toml';
  * } & toml.JsonMap} NetlifyConfig
  */
 
-/**
- * TODO(serhalp) Replace this custom type with an import from `@netlify/edge-functions`,
- * once that type is fixed to include `excludedPath` and `function`.
- * @typedef {{
- *	 functions: Array<
- *		 | {
- *				 function: string;
- *				 path: string;
- *				 excludedPath?: string | string[];
- *		   }
- *		 | {
- *				 function: string;
- *				 pattern: string;
- *				 excludedPattern?: string | string[];
- *		   }
- *	 >;
- *	 version: 1;
- *	 }} HandlerManifest
- */
-
 const name = '@sveltejs/adapter-netlify';
 const files = fileURLToPath(new URL('./files', import.meta.url).href);
 
@@ -102,14 +82,24 @@ 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 });
 			}
 		},
 
@@ -127,18 +117,21 @@ export default function ({ split = false, edge = edge_set_in_env_var } = {}) {
 		}
 	};
 }
+
 /**
  * @param { object } params
  * @param {import('@sveltejs/kit').Builder} 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`, {
@@ -148,20 +141,79 @@ async function generate_edge_functions({ builder }) {
 		}
 	});
 
-	const manifest = builder.generateManifest({
-		relativePath
+	await bundle_edge_function({ builder, name: 'render', reroute_middleware });
+}
+
+/**
+ * @param {object} params
+ * @param {import('@sveltejs/kit').Builder} 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...');
+
+	const tmp = builder.getBuildDirectory('netlify-tmp');
+	builder.rimraf(tmp);
+	builder.mkdirp(tmp);
+
+	builder.mkdirp('.netlify/edge-functions');
+
+	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 {import('@sveltejs/kit').Builder} 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`);
 
+	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> }} */
 	// 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 path = '/*';
 	// We only need to specify paths without the trailing slash because
 	// Netlify will handle the optional trailing slash for us
-	const excludedPath = [
+	const excluded = [
 		// Contains static files
 		`/${builder.getAppPath()}/*`,
 		...builder.prerendered.paths,
@@ -179,49 +231,29 @@ async function generate_edge_functions({ builder }) {
 		'/.netlify/*'
 	];
 
-	/** @type {HandlerManifest} */
+	/** @type {import('@netlify/edge-functions').Manifest} */
 	const edge_manifest = {
 		functions: [
 			{
-				function: 'render',
+				function: name,
 				path,
-				excludedPath
+				excludedPath: /** @type {`/${string}`[]} */ (excluded)
 			}
 		],
 		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 {object} params
  * @param {import('@sveltejs/kit').Builder} 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[]} */
@@ -282,7 +314,8 @@ 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`;
@@ -296,7 +329,8 @@ 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

@@ -34,19 +34,23 @@
 	"scripts": {
 		"dev": "node -e \"fs.rmSync('files', { force: true, recursive: true })\" && rollup -cw",
 		"build": "node -e \"fs.rmSync('files', { force: true, recursive: true })\" && rollup -c && node -e \"fs.cpSync('src/edge.js', 'files/edge.js')\"",
-		"test": "vitest run",
 		"check": "tsc",
 		"lint": "prettier --check .",
 		"format": "pnpm lint --write",
-		"prepublishOnly": "pnpm build"
+		"prepublishOnly": "pnpm build",
+		"test": "pnpm test:unit && pnpm test:integration",
+		"test:unit": "vitest run",
+		"test:integration": "pnpm build && pnpm -r --workspace-concurrency 1 --filter=\"./test/**\" test"
 	},
 	"dependencies": {
 		"@iarna/toml": "^2.2.5",
 		"esbuild": "^0.25.4",
 		"set-cookie-parser": "^2.6.0"
 	},
 	"devDependencies": {
+		"@netlify/edge-functions": "^2.11.1",
 		"@netlify/functions": "^3.0.0",
+		"@playwright/test": "^1.44.1",
 		"@rollup/plugin-commonjs": "^28.0.1",
 		"@rollup/plugin-json": "^6.1.0",
 		"@rollup/plugin-node-resolve": "^16.0.0",
@@ -59,6 +63,6 @@
 		"vitest": "^3.1.1"
 	},
 	"peerDependencies": {
-		"@sveltejs/kit": "^2.4.0"
+		"@sveltejs/kit": "^2.19.0"
 	}
 }