Sequence (#2222)

* feat: allow handle hooks to use middlewares

* test: add test for hooks sequence

* use lowercase header names (tests appear to fail otherwise?)

* fix: always pass request to resolve

* rename handles to handlers

* use test/apps/basics to test sequence, rather than creating separate app

* handles -> handlers

Co-authored-by: Maxime LUCE <[email protected]>

Author: Rich-Harris

packages/kit/package.json

@@ -71,6 +71,9 @@
 		"./node": {
 			"import": "./dist/node.js"
 		},
+		"./hooks": {
+			"import": "./dist/hooks.js"
+		},
 		"./install-fetch": {
 			"import": "./dist/install-fetch.js"
 		},

packages/kit/rollup.config.js

@@ -48,6 +48,7 @@ export default [
 			cli: 'src/cli.js',
 			ssr: 'src/runtime/server/index.js',
 			node: 'src/core/node/index.js',
+			hooks: 'src/runtime/hooks.js',
 			'install-fetch': 'src/install-fetch.js',
 			'adapter-utils': 'src/core/adapter-utils.js'
 		},

packages/kit/src/runtime/hooks.js

@@ -0,0 +1,26 @@
+/**
+ * @param {...import('types/hooks').Handle} handlers
+ * @returns {import('types/hooks').Handle}
+ */
+export function sequence(...handlers) {
+	const length = handlers.length;
+	if (!length) return ({ request, resolve }) => resolve(request);
+
+	return ({ request, resolve }) => {
+		return apply_handle(0, request);
+
+		/**
+		 * @param {number} i
+		 * @param {import('types/hooks').ServerRequest} request
+		 * @returns {import('types/helper').MaybePromise<import('types/hooks').ServerResponse>}
+		 */
+		function apply_handle(i, request) {
+			const handle = handlers[i];
+
+			return handle({
+				request,
+				resolve: i < length - 1 ? (request) => apply_handle(i + 1, request) : resolve
+			});
+		}
+	};
+}

packages/kit/test/apps/basics/src/hooks.js

@@ -1,27 +1,33 @@
+import { sequence } from '../../../../src/runtime/hooks';
 import cookie from 'cookie';
 
 /** @type {import('@sveltejs/kit').GetSession} */
 export function getSession(request) {
 	return request.locals;
 }
 
-/** @type {import('@sveltejs/kit').Handle} */
-export async function handle({ request, resolve }) {
-	const cookies = cookie.parse(request.headers.cookie || '');
+export const handle = sequence(
+	({ request, resolve }) => {
+		request.locals.answer = 42;
+		return resolve(request);
+	},
+	({ request, resolve }) => {
+		const cookies = cookie.parse(request.headers.cookie || '');
+		request.locals.name = cookies.name;
+		return resolve(request);
+	},
+	async ({ request, resolve }) => {
+		const response = await resolve(request);
 
-	request.locals.answer = 42;
-	request.locals.name = cookies.name;
-
-	const response = await resolve(request);
-
-	return {
-		...response,
-		headers: {
-			...response.headers,
-			'Set-Cookie': 'name=SvelteKit; path=/; HttpOnly'
-		}
-	};
-}
+		return {
+			...response,
+			headers: {
+				...response.headers,
+				'Set-Cookie': 'name=SvelteKit; path=/; HttpOnly'
+			}
+		};
+	}
+);
 
 /** @type {import('@sveltejs/kit').ServerFetch} */
 export async function serverFetch(request) {

packages/kit/types/ambient-modules.d.ts

@@ -129,3 +129,15 @@ declare module '$service-worker' {
 	 */
 	export const timestamp: number;
 }
+
+declare module '@sveltejs/kit/hooks' {
+	type Handle = import('@sveltejs/kit').Handle;
+
+	/**
+	 * Utility function that allows chaining `handle` functions in a
+	 * middleware-like manner.
+	 *
+	 * @param handlers The chain of `handle` functions
+	 */
+	export function sequence(...handlers: Handle[]): Handle;
+}