Fix(node): Custom headers are not present in responses from standalone Node server in preview mode

.changeset/spotty-dryers-hear.md

@@ -0,0 +1,6 @@
+---
+"@astrojs/node": patch
+"astro": patch
+---
+
+Fixes custom headers are not added to the Node standalone server responses in preview mode

packages/astro/src/@types/astro.ts

@@ -2748,6 +2748,7 @@ export interface PreviewServerParams {
 	port: number;
 	base: string;
 	logger: AstroIntegrationLogger;
+	headers?: OutgoingHttpHeaders;
 }
 
 export type CreatePreviewServer = (

packages/astro/src/core/preview/index.ts

@@ -75,6 +75,7 @@ export default async function preview(inlineConfig: AstroInlineConfig): Promise<
 		port: settings.config.server.port,
 		base: settings.config.base,
 		logger: new AstroIntegrationLogger(logger.options, settings.adapter.name),
+		headers: settings.config.server.headers,
 	});
 
 	return server;

packages/integrations/node/src/preview.ts

@@ -36,6 +36,19 @@ const createPreviewServer: CreatePreviewServer = async function (preview) {
 	const host = preview.host ?? 'localhost';
 	const port = preview.port ?? 4321;
 	const server = createServer(ssrHandler, host, port);
+
+	// If user specified custom headers append a listener
+	// to the server to add those headers to response
+	if (preview.headers) {
+		server.server.addListener('request', (_, res) => {
+			if (res.statusCode === 200) {
+				for (const [name, value] of Object.entries(preview.headers ?? {})) {
+					if (value) res.setHeader(name, value);
+				}
+			}
+		});
+	}
+
 	logListeningOn(preview.logger, server.server, options);
 	await new Promise<void>((resolve, reject) => {
 		server.server.once('listening', resolve);

packages/integrations/node/test/fixtures/preview-headers/package.json

@@ -0,0 +1,9 @@
+{
+  "name": "@test/nodejs-preview-headers",
+  "version": "0.0.0",
+  "private": true,
+  "dependencies": {
+    "astro": "workspace:*",
+    "@astrojs/node": "workspace:*"
+  }
+}

packages/integrations/node/test/fixtures/preview-headers/src/pages/index.astro

@@ -0,0 +1 @@
+Hello!

packages/integrations/node/test/preview-headers.test.js

@@ -0,0 +1,38 @@
+import * as assert from 'node:assert/strict';
+import { after, before, describe, it } from 'node:test';
+import nodejs from '../dist/index.js';
+import { loadFixture } from './test-utils.js';
+
+describe('Astro preview headers', () => {
+	/** @type {import('./test-utils').Fixture} */
+	let fixture;
+	let devPreview;
+	const headers = {
+		astro: 'test',
+	};
+
+	before(async () => {
+		fixture = await loadFixture({
+			root: './fixtures/preview-headers/',
+			output: 'server',
+			adapter: nodejs({ mode: 'standalone' }),
+			server: {
+				headers
+			},
+		});
+		await fixture.build();
+		devPreview = await fixture.preview();
+	});
+
+	after(async () => {
+		await devPreview.stop();
+	});
+
+	describe('Preview Headers', () => {
+		it('returns custom headers for valid URLs', async () => {
+			const result = await fixture.fetch('/');
+			assert.equal(result.status, 200);
+			assert.equal(Object.fromEntries(result.headers).astro, headers.astro);
+		});
+	});
+});