Unflag Server Islands (#11955)

* Unflag Server Islands

* update example

* Add changeset

* Only append serverIslands route if there is one

* Update .changeset/strange-sheep-film.md

Co-authored-by: Sarah Rainsberger <sarah@rainsberger.ca>

* check buildoutput instead

* Update packages/astro/src/core/errors/errors-data.ts

Co-authored-by: Erika <3019731+Princesseuh@users.noreply.github.com>

* remove flag

---------

Co-authored-by: Sarah Rainsberger <sarah@rainsberger.ca>
Co-authored-by: Erika <3019731+Princesseuh@users.noreply.github.com>

.changeset/strange-sheep-film.md

@@ -0,0 +1,40 @@
+---
+'astro': minor
+---
+
+[Server Islands](https://astro.build/blog/future-of-astro-server-islands/) introduced behind an experimental flag in [v4.12.0](https://github.com/withastro/astro/blob/main/packages/astro/CHANGELOG.md#4120) is no longer experimental and is available for general use.
+
+Server islands are Astro's solution for highly cacheable pages of mixed static and dynamic content. They allow you to specify components that should run on the server, allowing the rest of the page to be more aggressively cached, or even generated statically.
+
+Turn any `.astro` component into a server island by adding the `server:defer` directive and optionally, fallback placeholder content. It will be rendered dynamically at runtime outside the context of the rest of the page, allowing you to add longer cache headers for the pages, or even prerender them.
+
+```astro
+---
+import Avatar from '../components/Avatar.astro';
+import GenericUser from '../components/GenericUser.astro';
+---
+<header>
+  <h1>Page Title</h1>
+  <div class="header-right">
+    <Avatar server:defer>
+      <GenericUser slot="fallback" />
+    </Avatar>
+  </div>
+</header>
+```
+
+If you were previously using this feature, please remove the experimental flag from your Astro config:
+
+```diff
+import { defineConfig } from 'astro/config';
+
+export default defineConfig({
+  experimental {
+-    serverIslands: true,
+  },
+});
+```
+
+If you have been waiting for stabilization before using server islands, you can now do so.
+
+Please see the [server island documentation](https://docs.astro.build/en/guides/server-islands/) for more about this feature.

examples/server-islands/astro.config.mjs

@@ -12,7 +12,4 @@ export default defineConfig({
 		tailwind({ applyBaseStyles: false })
 	],
 	devToolbar: { enabled: false },
-	experimental: {
-		serverIslands: true,
-	}
 });

packages/astro/e2e/fixtures/server-islands-key/astro.config.mjs

@@ -6,7 +6,4 @@ export default defineConfig({
 	output: 'server',
 	adapter: node({ mode: 'standalone' }),
 	integrations: [],
-	experimental: {
-		serverIslands: true,
-	}
 });

packages/astro/e2e/fixtures/server-islands/astro.config.mjs

@@ -10,7 +10,4 @@ export default defineConfig({
 	adapter: nodejs({ mode: 'standalone' }),
 	integrations: [react(), mdx()],
 	trailingSlash: process.env.TRAILING_SLASH ?? 'always',
-	experimental: {
-		serverIslands: true,
-	}
 });

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

@@ -210,6 +210,13 @@ class AstroBuilder {
 		};
 
 		const { internals, ssrOutputChunkNames, contentFileNames } = await viteBuild(opts);
+
+		const hasServerIslands = this.settings.serverIslandNameMap.size > 0;
+		// Error if there are server islands but no adapter provided.
+		if(hasServerIslands && this.settings.buildOutput !== 'server') {
+			throw new AstroError(AstroErrorData.NoAdapterInstalledServerIslands);
+		}
+
 		await staticBuild(opts, internals, ssrOutputChunkNames, contentFileNames);
 
 		// Write any additionally generated assets to disk.
@@ -230,11 +237,7 @@ class AstroBuilder {
 			routes: Object.values(allPages)
 				.flat()
 				.map((pageData) => pageData.route)
-				.concat(
-					this.settings.config.experimental.serverIslands
-						? [getServerIslandRouteData(this.settings.config)]
-						: [],
-				),
+				.concat(hasServerIslands ? getServerIslandRouteData(this.settings.config) : []),
 			logging: this.logger,
 			cacheManifest: internals.cacheManifestUsed,
 		});

packages/astro/src/core/build/plugins/plugin-ssr.ts

@@ -171,13 +171,10 @@ function generateSSRCode(settings: AstroSettings, adapter: AstroAdapter, middlew
 		`import * as serverEntrypointModule from '${ADAPTER_VIRTUAL_MODULE_ID}';`,
 		`import { manifest as defaultManifest } from '${SSR_MANIFEST_VIRTUAL_MODULE_ID}';`,
 		edgeMiddleware ? `` : `import { onRequest as middleware } from '${middlewareId}';`,
-		settings.config.experimental.serverIslands
-			? `import { serverIslandMap } from '${VIRTUAL_ISLAND_MAP_ID}';`
-			: '',
+		`import { serverIslandMap } from '${VIRTUAL_ISLAND_MAP_ID}';`,
 	];
 
 	const contents = [
-		settings.config.experimental.serverIslands ? '' : `const serverIslandMap = new Map()`,
 		edgeMiddleware ? `const middleware = (_, next) => next()` : '',
 		`const _manifest = Object.assign(defaultManifest, {`,
 		`    pageMap,`,

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

@@ -92,7 +92,6 @@ export const ASTRO_CONFIG_DEFAULTS = {
 	experimental: {
 		contentCollectionCache: false,
 		clientPrerender: false,
-		serverIslands: false,
 		contentIntellisense: false,
 	},
 } satisfies AstroUserConfig & { server: { open: boolean } };
@@ -530,10 +529,6 @@ export const AstroConfigSchema = z.object({
 				.boolean()
 				.optional()
 				.default(ASTRO_CONFIG_DEFAULTS.experimental.clientPrerender),
-			serverIslands: z
-				.boolean()
-				.optional()
-				.default(ASTRO_CONFIG_DEFAULTS.experimental.serverIslands),
 			contentIntellisense: z
 				.boolean()
 				.optional()

packages/astro/src/core/create-vite.ts

@@ -158,7 +158,7 @@ export async function createVite(
 			astroInternationalization({ settings }),
 			vitePluginActions({ fs, settings }),
 			vitePluginUserActions({ settings }),
-			settings.config.experimental.serverIslands && vitePluginServerIslands({ settings }),
+			vitePluginServerIslands({ settings }),
 			astroContainer(),
 		],
 		publicDir: fileURLToPath(settings.config.publicDir),

packages/astro/src/core/errors/errors-data.ts

@@ -412,6 +412,19 @@ export const AdapterSupportOutputMismatch = {
 		`The \`${adapterName}\` adapter is configured to output a static website, but the project contains server-rendered pages. Please install and configure the appropriate server adapter for your final deployment.`,
 } satisfies ErrorData;
 
+/**
+ * @docs
+ * @see
+ * - [Server-side Rendering](https://docs.astro.build/en/guides/server-side-rendering/)
+ * @description
+ * To use server islands, the same constraints exist as for sever-side rendering, so an adapter is needed.
+ */
+export const NoAdapterInstalledServerIslands = {
+	name: 'NoAdapterInstalledServerIslands',
+	title: 'Cannot use Server Islands without an adapter.',
+	message: `Cannot use server islands without an adapter. Please install and configure the appropriate server adapter for your final deployment.`,
+	hint: 'See https://docs.astro.build/en/guides/server-side-rendering/ for more information.',
+} satisfies ErrorData;
 /**
  * @docs
  * @description

packages/astro/test/fixtures/server-islands/hybrid/astro.config.mjs

@@ -6,7 +6,4 @@ export default defineConfig({
   integrations: [
     svelte()
   ],
-  experimental: {
-    serverIslands: true,
-  }
 });

packages/astro/test/fixtures/server-islands/ssr/astro.config.mjs

@@ -8,8 +8,5 @@ export default defineConfig({
   integrations: [
     svelte()
   ],
-  experimental: {
-    serverIslands: true,
-  }
 });
 

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

@@ -63,13 +63,14 @@ describe('Server islands', () => {
 		before(async () => {
 			fixture = await loadFixture({
 				root: './fixtures/server-islands/hybrid',
-				adapter: testAdapter(),
 			});
 		});
 
 		describe('build', () => {
 			before(async () => {
-				await fixture.build();
+				await fixture.build({
+					adapter: testAdapter()
+				});
 			});
 
 			it('Omits the island HTML from the static HTML', async () => {
@@ -83,5 +84,18 @@ describe('Server islands', () => {
 				assert.equal(serverIslandScript.length, 1, 'has the island script');
 			});
 		});
+
+		describe('build (no adapter)', () => {
+			it('Errors during the build', async () => {
+				try {
+					await fixture.build({
+						adapter: undefined
+					});
+					assert.equal(true, false, 'should not have succeeded');
+				} catch(err) {
+					assert.equal(err.title, 'Cannot use Server Islands without an adapter.');
+				}
+			});
+		});
 	});
 });