Add server.headers option

With this new `server.headers` option, the users can specify
custom headers for `astro dev` and `astro preview` servers.

This is useful when they want to build a website requiring
specific response headers such as `Cross-Origin-Opener-Policy`.

.changeset/light-moose-attend.md

@@ -0,0 +1,5 @@
+---
+'astro': minor
+---
+
+Add `server.headers` option

packages/astro/src/core/config/schema.ts

@@ -9,6 +9,7 @@ import { fileURLToPath } from 'url';
 import { z } from 'zod';
 import { appendForwardSlash, prependForwardSlash, trimSlashes } from '../path.js';
 import { isObject } from '../util.js';
+import { OutgoingHttpHeaders } from 'http';
 
 const ASTRO_CONFIG_DEFAULTS: AstroUserConfig & any = {
 	root: '.',
@@ -125,6 +126,7 @@ export const AstroConfigSchema = z.object({
 					.optional()
 					.default(ASTRO_CONFIG_DEFAULTS.server.host),
 				port: z.number().optional().default(ASTRO_CONFIG_DEFAULTS.server.port),
+				headers: z.custom<OutgoingHttpHeaders>().optional(),
 			})
 			.optional()
 			.default({})

packages/astro/src/core/dev/container.ts

@@ -65,7 +65,7 @@ export async function createContainer(params: CreateContainerParams = {}): Promi
 		logging,
 		isRestart,
 	});
-	const { host } = settings.config.server;
+	const { host, headers } = settings.config.server;
 
 	// The client entrypoint for renderers. Since these are imported dynamically
 	// we need to tell Vite to preoptimize them.
@@ -76,7 +76,7 @@ export async function createContainer(params: CreateContainerParams = {}): Promi
 	const viteConfig = await createVite(
 		{
 			mode: 'development',
-			server: { host },
+			server: { host, headers },
 			optimizeDeps: {
 				include: rendererClientEntries,
 			},

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

@@ -24,10 +24,10 @@ export default async function preview(
 	});
 	await runHookConfigDone({ settings: settings, logging: logging });
 	const host = getResolvedHostForHttpServer(settings.config.server.host);
-	const { port } = settings.config.server;
+	const { port, headers } = settings.config.server;
 
 	if (settings.config.output === 'static') {
-		const server = await createStaticPreviewServer(settings, { logging, host, port });
+		const server = await createStaticPreviewServer(settings, { logging, host, port, headers });
 		return server;
 	}
 	if (!settings.adapter) {

packages/astro/src/core/preview/static-preview-server.ts

@@ -3,7 +3,7 @@ import type { AstroSettings } from '../../@types/astro';
 import type { LogOptions } from '../logger/core';
 
 import fs from 'fs';
-import http from 'http';
+import http, { OutgoingHttpHeaders } from 'http';
 import { performance } from 'perf_hooks';
 import sirv from 'sirv';
 import { fileURLToPath } from 'url';
@@ -24,7 +24,17 @@ const HAS_FILE_EXTENSION_REGEXP = /^.*\.[^\\]+$/;
 /** The primary dev action */
 export default async function createStaticPreviewServer(
 	settings: AstroSettings,
-	{ logging, host, port }: { logging: LogOptions; host: string | undefined; port: number }
+	{
+		logging,
+		host,
+		port,
+		headers,
+	}: {
+		logging: LogOptions;
+		host: string | undefined;
+		port: number;
+		headers: OutgoingHttpHeaders | undefined;
+	}
 ): Promise<PreviewServer> {
 	const startServerTime = performance.now();
 	const defaultOrigin = 'http://localhost';
@@ -35,6 +45,11 @@ export default async function createStaticPreviewServer(
 		dev: true,
 		etag: true,
 		maxAge: 0,
+		setHeaders: (res, pathname, stats) => {
+			for (const [name, value] of Object.entries(headers ?? {})) {
+				if (value) res.setHeader(name, value);
+			}
+		},
 	});
 	// Create the preview server, send static files out of the `dist/` directory.
 	const server = http.createServer((req, res) => {

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

@@ -144,6 +144,11 @@ export async function handleRoute(
 		clientAddress: buildingToSSR ? req.socket.remoteAddress : undefined,
 	});
 
+	// Set user specified headers to response object.
+	for (const [name, value] of Object.entries(config.server.headers ?? {})) {
+		if (value) res.setHeader(name, value);
+	}
+
 	// attempt to get static paths
 	// if this fails, we have a bad URL match!
 	const paramsAndPropsRes = await getParamsAndProps({

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

@@ -0,0 +1,39 @@
+import { expect } from 'chai';
+import { loadFixture } from './test-utils.js';
+
+describe('Astro dev headers', () => {
+	let fixture;
+	let devServer;
+	const headers = {
+		'x-astro': 'test',
+	};
+
+	before(async () => {
+		fixture = await loadFixture({
+			root: './fixtures/astro-dev-headers/',
+			server: {
+				headers,
+			},
+		});
+		await fixture.build();
+		devServer = await fixture.startDevServer();
+	});
+
+	after(async () => {
+		await devServer.stop();
+	});
+
+	describe('dev', () => {
+		it('returns custom headers for valid URLs', async () => {
+			const result = await fixture.fetch('/');
+			expect(result.status).to.equal(200);
+			expect(Object.fromEntries(result.headers)).to.include(headers);
+		});
+
+		it('does not return custom headers for invalid URLs', async () => {
+			const result = await fixture.fetch('/bad-url');
+			expect(result.status).to.equal(404);
+			expect(Object.fromEntries(result.headers)).not.to.include(headers);
+		});
+	});
+});

packages/astro/test/astro-preview-headers.test.js

@@ -0,0 +1,40 @@
+import { expect } from 'chai';
+import { loadFixture } from './test-utils.js';
+
+describe('Astro preview headers', () => {
+	let fixture;
+	let previewServer;
+	const headers = {
+		astro: 'test',
+	};
+
+	before(async () => {
+		fixture = await loadFixture({
+			root: './fixtures/astro-preview-headers/',
+			server: {
+				headers,
+			},
+		});
+		await fixture.build();
+		previewServer = await fixture.preview();
+	});
+
+	// important: close preview server (free up port and connection)
+	after(async () => {
+		await previewServer.stop();
+	});
+
+	describe('preview', () => {
+		it('returns custom headers for valid URLs', async () => {
+			const result = await fixture.fetch('/');
+			expect(result.status).to.equal(200);
+			expect(Object.fromEntries(result.headers)).to.include(headers);
+		});
+
+		it('does not return custom headers for invalid URLs', async () => {
+			const result = await fixture.fetch('/bad-url');
+			expect(result.status).to.equal(404);
+			expect(Object.fromEntries(result.headers)).not.to.include(headers);
+		});
+	});
+});

packages/astro/test/fixtures/astro-dev-headers/package.json

@@ -0,0 +1,8 @@
+{
+  "name": "@test/astro-dev-headers",
+  "version": "0.0.0",
+  "private": true,
+  "dependencies": {
+    "astro": "workspace:*"
+  }
+}

packages/astro/test/fixtures/astro-dev-headers/src/pages/index.astro

@@ -0,0 +1,8 @@
+<html>
+  <head>
+  </head>
+  <body>
+    <h1>Hello world!</h1>
+  </body>
+</html>
+

packages/astro/test/fixtures/astro-preview-headers/package.json

@@ -0,0 +1,8 @@
+{
+  "name": "@test/astro-preview-headers",
+  "version": "0.0.0",
+  "private": true,
+  "dependencies": {
+    "astro": "workspace:*"
+  }
+}

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

@@ -0,0 +1,8 @@
+<html>
+  <head>
+  </head>
+  <body>
+    <h1>Hello world!</h1>
+  </body>
+</html>
+