[fix] default handlers for head (#3903)

* fix: respond to HEAD requests in endpoints

* chore: cleanup

* fix: handle head requests when loading shadow data

* add changeset

* refactor: normalize request method without replace

* fix: use  instead of empty string for HEAD response body

* Apply suggestions from code review

Co-authored-by: Rich Harris <hello@rich-harris.dev>

* code style tweaks

* remove more type annotations

* more code style

* Apply suggestions from code review

Co-authored-by: Rich Harris <hello@rich-harris.dev>

Co-authored-by: Rich Harris <hello@rich-harris.dev>

.changeset/chatty-impalas-smash.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+handle HEAD requests in endpoints

packages/kit/src/runtime/server/endpoint.js

@@ -1,6 +1,6 @@
 import { to_headers } from '../../utils/http.js';
 import { hash } from '../hash.js';
-import { is_pojo } from './utils.js';
+import { is_pojo, normalize_request_method } from './utils.js';
 
 /** @param {string} body */
 function error(body) {
@@ -40,9 +40,14 @@ export function is_text(content_type) {
  * @returns {Promise<Response | undefined>}
  */
 export async function render_endpoint(event, mod) {
+	const method = normalize_request_method(event);
+
 	/** @type {import('types/endpoint').RequestHandler} */
-	const handler = mod[event.request.method.toLowerCase().replace('delete', 'del')]; // 'delete' is a reserved word
+	let handler = mod[method];
 
+	if (!handler && method === 'head') {
+		handler = mod.get;
+	}
 	if (!handler) {
 		return;
 	}
@@ -92,7 +97,7 @@ export async function render_endpoint(event, mod) {
 		}
 	}
 
-	return new Response(normalized_body, {
+	return new Response(method !== 'head' ? normalized_body : undefined, {
 		status,
 		headers
 	});

packages/kit/src/runtime/server/page/load_node.js

@@ -4,7 +4,7 @@ import { s } from '../../../utils/misc.js';
 import { escape_json_in_html } from '../../../utils/escape.js';
 import { is_root_relative, resolve } from '../../../utils/url.js';
 import { create_prerendering_url_proxy } from './utils.js';
-import { is_pojo, lowercase_keys } from '../utils.js';
+import { is_pojo, lowercase_keys, normalize_request_method } from '../utils.js';
 import { coalesce_to_error } from '../../../utils/error.js';
 
 /**
@@ -385,8 +385,8 @@ async function load_shadow_data(route, event, options, prerender) {
 			throw new Error('Cannot prerender pages that have shadow endpoints with mutative methods');
 		}
 
-		const method = event.request.method.toLowerCase().replace('delete', 'del');
-		const handler = mod[method];
+		const method = normalize_request_method(event);
+		const handler = method === 'head' ? mod.head || mod.get : mod[method];
 
 		if (!handler) {
 			return {
@@ -402,7 +402,7 @@ async function load_shadow_data(route, event, options, prerender) {
 			body: {}
 		};
 
-		if (method !== 'get') {
+		if (method !== 'get' && method !== 'head') {
 			const result = await handler(event);
 
 			if (result.fallthrough) return result;
@@ -426,8 +426,9 @@ async function load_shadow_data(route, event, options, prerender) {
 			data.body = body;
 		}
 
-		if (mod.get) {
-			const result = await mod.get.call(null, event);
+		const get = (method === 'head' && mod.head) || mod.get;
+		if (get) {
+			const result = await get(event);
 
 			if (result.fallthrough) return result;
 

packages/kit/src/runtime/server/utils.js

@@ -49,3 +49,11 @@ export function is_pojo(body) {
 
 	return true;
 }
+/**
+ * @param {import('types/hooks').RequestEvent} event
+ * @returns string
+ */
+export function normalize_request_method(event) {
+	const method = event.request.method.toLowerCase();
+	return method === 'delete' ? 'del' : method; // 'delete' is a reserved word
+}

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

@@ -431,6 +431,38 @@ test.describe.parallel('Shadowed pages', () => {
 
 		expect(await response.json()).toEqual({ answer: 42 });
 	});
+
+	test('responds to HEAD requests from endpoint', async ({ request }) => {
+		const url = '/shadowed/simple';
+
+		const opts = {
+			headers: {
+				accept: 'application/json'
+			}
+		};
+
+		const responses = {
+			head: await request.head(url, opts),
+			get: await request.get(url, opts)
+		};
+
+		const headers = {
+			head: responses.head.headers(),
+			get: responses.get.headers()
+		};
+
+		expect(responses.head.status()).toBe(200);
+		expect(responses.get.status()).toBe(200);
+		expect(await responses.head.text()).toBe('');
+		expect(await responses.get.json()).toEqual({ answer: 42 });
+
+		['date', 'transfer-encoding'].forEach((name) => {
+			delete headers.head[name];
+			delete headers.get[name];
+		});
+
+		expect(headers.head).toEqual(headers.get);
+	});
 });
 
 test.describe.parallel('Endpoints', () => {
@@ -459,6 +491,32 @@ test.describe.parallel('Endpoints', () => {
 		expect(response.headers()['set-cookie']).toBeDefined();
 	});
 
+	test('HEAD with matching headers but without body', async ({ request }) => {
+		const url = '/endpoint-output/body';
+
+		const responses = {
+			head: await request.head(url),
+			get: await request.get(url)
+		};
+
+		const headers = {
+			head: responses.head.headers(),
+			get: responses.get.headers()
+		};
+
+		expect(responses.head.status()).toBe(200);
+		expect(responses.get.status()).toBe(200);
+		expect(await responses.head.text()).toBe('');
+		expect(await responses.get.text()).toBe('{}');
+
+		['date', 'transfer-encoding'].forEach((name) => {
+			delete headers.head[name];
+			delete headers.get[name];
+		});
+
+		expect(headers.head).toEqual(headers.get);
+	});
+
 	test('200 status by default', async ({ request }) => {
 		const response = await request.get('/endpoint-output/body');
 		expect(/** @type {import('@playwright/test').APIResponse} */ (response).status()).toBe(200);