allow /favicon.ico to be a valid route (#5046)

* allow /favicon.ico to be a valid route - closes #4968

* Update packages/kit/src/runtime/server/index.js

* Update .changeset/young-flies-camp.md

Co-authored-by: Maurício Kishi <mrkishi@users.noreply.github.com>

Co-authored-by: Maurício Kishi <mrkishi@users.noreply.github.com>

.changeset/young-flies-camp.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+[breaking] stop suppressing `/favicon.ico` requests, handle them as a valid route

packages/kit/src/core/dev/plugin.js

@@ -205,8 +205,6 @@ export async function create_plugin(config) {
 							}
 						}
 
-						if (req.url === '/favicon.ico') return not_found(res);
-
 						if (!decoded.startsWith(config.kit.paths.base)) {
 							return not_found(res, `Not found (did you mean ${config.kit.paths.base + req.url}?)`);
 						}

packages/kit/test/apps/basics/src/routes/favicon.ico.js

@@ -0,0 +1,7 @@
+export function get() {
+	return {
+		body: {
+			surprise: 'lol'
+		}
+	};
+}

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

@@ -2502,6 +2502,14 @@ test.describe.parallel('Routing', () => {
 		await page.goto('/static');
 		expect(await page.textContent('h1')).toBe('hello');
 	});
+
+	test('/favicon.ico is a valid route', async ({ request }) => {
+		const response = await request.get('/favicon.ico');
+		expect(response.status()).toBe(200);
+
+		const data = await response.json();
+		expect(data).toEqual({ surprise: 'lol' });
+	});
 });
 
 test.describe.parallel('Session', () => {