Call server island early so it can set headers

.changeset/rotten-dodos-judge.md

@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Call server island early so it can set headers

packages/astro/src/core/server-islands/endpoint.ts

@@ -4,6 +4,7 @@ import {
 	renderComponent,
 	renderTemplate,
 } from '../../runtime/server/index.js';
+import { isAstroComponentFactory } from '../../runtime/server/render/astro/factory.js';
 import { createSlotValueFromString } from '../../runtime/server/render/slot.js';
 import type { ComponentInstance, ManifestData } from '../../types/astro.js';
 import type { RouteData, SSRManifest } from '../../types/public/internal.js';
@@ -120,17 +121,31 @@ export function createEndpoint(manifest: SSRManifest) {
 
 		const key = await manifest.key;
 		const encryptedProps = data.encryptedProps;
+
 		const propString = await decryptString(key, encryptedProps);
 		const props = JSON.parse(propString);
 
 		const componentModule = await imp();
-		const Component = (componentModule as any)[data.componentExport];
+		let Component = (componentModule as any)[data.componentExport];
 
 		const slots: ComponentSlots = {};
 		for (const prop in data.slots) {
 			slots[prop] = createSlotValueFromString(data.slots[prop]);
 		}
 
+		// Wrap Astro components so we can set propagation to
+		// `self` which is needed to force the runtime to wait
+		// on the component before sending out the response headers.
+		// This allows the island to set headers (cookies).
+		if(isAstroComponentFactory(Component)) {
+			const ServerIsland = Component;
+			Component = function(this: typeof ServerIsland, ...args: Parameters<typeof ServerIsland>) {
+				return ServerIsland.apply(this, args);
+			};
+			Object.assign(Component, ServerIsland);
+			Component.propagation = 'self';
+		}
+
 		return renderTemplate`${renderComponent(result, 'Component', Component, props, slots)}`;
 	};
 

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

@@ -4,7 +4,7 @@ import { IncomingMessage } from 'node:http';
 import type * as vite from 'vite';
 import type { SSRManifest, SSRManifestI18n } from '../core/app/types.js';
 import { warnMissingAdapter } from '../core/dev/adapter-validation.js';
-import { createKey } from '../core/encryption.js';
+import { createKey, getEnvironmentKey, hasEnvironmentKey } from '../core/encryption.js';
 import { getViteErrorPayload } from '../core/errors/dev/index.js';
 import { AstroError, AstroErrorData } from '../core/errors/index.js';
 import { patchOverlay } from '../core/errors/overlay.js';
@@ -168,7 +168,7 @@ export function createDevelopmentManifest(settings: AstroSettings): SSRManifest
 		checkOrigin:
 			(settings.config.security?.checkOrigin && settings.buildOutput === 'server') ?? false,
 		envGetSecretEnabled: false,
-		key: createKey(),
+		key: hasEnvironmentKey() ? getEnvironmentKey() : createKey(),
 		middleware() {
 			return {
 				onRequest: NOOP_MIDDLEWARE_FN,

packages/astro/test/fixtures/server-islands/ssr/src/components/Island.astro

@@ -1,4 +1,5 @@
 ---
-
+await new Promise(resolve => setTimeout(resolve, 1));
+Astro.response.headers.set('X-Works', 'true');
 ---
 <h2 id="island">I'm an island</h2>

packages/astro/test/server-islands.test.js

@@ -19,11 +19,13 @@ describe('Server islands', () => {
 			let devServer;
 
 			before(async () => {
+				process.env.ASTRO_KEY = 'eKBaVEuI7YjfanEXHuJe/pwZKKt3LkAHeMxvTU7aR0M=';
 				devServer = await fixture.startDevServer();
 			});
 
 			after(async () => {
 				await devServer.stop();
+				delete process.env.ASTRO_KEY;
 			});
 
 			it('omits the islands HTML', async () => {
@@ -34,13 +36,31 @@ describe('Server islands', () => {
 				const serverIslandEl = $('h2#island');
 				assert.equal(serverIslandEl.length, 0);
 			});
+
+			it('island can set headers', async () => {
+				const res = await fixture.fetch('/_server-islands/Island', {
+					method: 'POST',
+					body: JSON.stringify({
+					        componentExport: 'default',
+					        encryptedProps: 'FC8337AF072BE5B1641501E1r8mLIhmIME1AV7UO9XmW9OLD',
+					        slots: {},
+					})
+				});
+				const works = res.headers.get('X-Works');
+				assert.equal(works, 'true', 'able to set header from server island');
+			});
 		});
 
 		describe('prod', () => {
 			before(async () => {
+				process.env.ASTRO_KEY = 'eKBaVEuI7YjfanEXHuJe/pwZKKt3LkAHeMxvTU7aR0M=';
 				await fixture.build();
 			});
 
+			after(async () => {
+				delete process.env.ASTRO_KEY;
+			});
+
 			it('omits the islands HTML', async () => {
 				const app = await fixture.loadTestAdapterApp();
 				const request = new Request('http://example.com/');