Fix returning images from endpoints in dev (#6163)

* fix(dev): Fix dev server responses not being encoded following the specified encoding

* test: Add test

* chore: changeset

.changeset/honest-pugs-hang.md

@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Fix returning hex / base64 images from endpoints not working in dev

packages/astro/src/vite-plugin-astro-server/route.ts

@@ -200,7 +200,7 @@ export async function handleRoute(
 			if (computedMimeType) {
 				contentType = computedMimeType;
 			}
-			const response = new Response(result.body, {
+			const response = new Response(Buffer.from(result.body, result.encoding), {
 				status: 200,
 				headers: {
 					'Content-Type': `${contentType};charset=utf-8`,

packages/astro/test/dev-routing.test.js

@@ -270,6 +270,15 @@ describe('Development Routing', () => {
 			const response = await fixture.fetch('/images/1.svg');
 			expect(response.headers.get('content-type')).to.match(/image\/svg\+xml/);
 		});
+
+		it('correct encoding when loading /images/hex.ts', async () => {
+			const response = await fixture.fetch('/images/hex');
+			const body = await response.arrayBuffer();
+			const hex = Buffer.from(body).toString('hex', 0, 4);
+
+			// Check if we have a PNG
+			expect(hex).to.equal('89504e47');
+		});
 	});
 
 	describe('file format routing', () => {

packages/astro/test/fixtures/with-endpoint-routes/src/pages/images/hex.ts

@@ -0,0 +1,9 @@
+import { readFileSync } from "node:fs";
+
+export async function get({ params, request }) {
+  const buffer = readFileSync(new URL('../../astro.png', import.meta.url));
+  return {
+    body: buffer.toString('hex'),
+    encoding: 'hex',
+  };
+}