Ensure before-hydration is only loaded when used (#4768)

* Ensure before-hydration is only loaded when used

* client fix + changeset

.changeset/fluffy-eyes-boil.md

@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+nsure before-hydration is only loaded when used

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

@@ -159,9 +159,15 @@ export class App {
 						throw new Error(`Unable to resolve [${specifier}]`);
 					}
 					const bundlePath = manifest.entryModules[specifier];
-					return bundlePath.startsWith('data:')
-						? bundlePath
-						: prependForwardSlash(joinPaths(manifest.base, bundlePath));
+					switch(true) {
+						case bundlePath.startsWith('data:'):
+						case bundlePath.length === 0: {
+							return bundlePath;
+						}
+						default: {
+							return prependForwardSlash(joinPaths(manifest.base, bundlePath));
+						}
+					}
 				},
 				route: routeData,
 				routeCache: this.#routeCache,

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

@@ -370,11 +370,8 @@ async function generatePath(
 			if (typeof hashedFilePath !== 'string') {
 				// If no "astro:scripts/before-hydration.js" script exists in the build,
 				// then we can assume that no before-hydration scripts are needed.
-				// Return this as placeholder, which will be ignored by the browser.
-				// TODO: In the future, we hope to run this entire script through Vite,
-				// removing the need to maintain our own custom Vite-mimic resolve logic.
 				if (specifier === BEFORE_HYDRATION_SCRIPT_ID) {
-					return 'data:text/javascript;charset=utf-8,//[no before-hydration script]';
+					return '';
 				}
 				throw new Error(`Cannot find the built path for ${specifier}`);
 			}

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

@@ -152,8 +152,8 @@ function buildManifest(
 
 	// HACK! Patch this special one.
 	if (!(BEFORE_HYDRATION_SCRIPT_ID in entryModules)) {
-		entryModules[BEFORE_HYDRATION_SCRIPT_ID] =
-			'data:text/javascript;charset=utf-8,//[no before-hydration script]';
+		// Set this to an empty string so that the runtime knows not to try and load this.
+		entryModules[BEFORE_HYDRATION_SCRIPT_ID] = '';
 	}
 
 	const ssrManifest: SerializedSSRManifest = {

packages/astro/src/runtime/server/astro-island.ts

@@ -56,7 +56,10 @@ declare const Astro: {
 				}
 				async childrenConnectedCallback() {
 					window.addEventListener('astro:hydrate', this.hydrate);
-					await import(this.getAttribute('before-hydration-url')!);
+					let beforeHydrationUrl = this.getAttribute('before-hydration-url');
+					if(beforeHydrationUrl) {
+						await import(beforeHydrationUrl);
+					}
 					this.start();
 				}
 				start() {

packages/astro/src/runtime/server/hydration.ts

@@ -151,7 +151,10 @@ export async function generateHydrateScript(
 
 	island.props['ssr'] = '';
 	island.props['client'] = hydrate;
-	island.props['before-hydration-url'] = await result.resolve('astro:scripts/before-hydration.js');
+	let beforeHydrationUrl = await result.resolve('astro:scripts/before-hydration.js');
+	if(beforeHydrationUrl.length) {
+		island.props['before-hydration-url'] = beforeHydrationUrl;
+	}
 	island.props['opts'] = escapeHTML(
 		JSON.stringify({
 			name: metadata.displayName,

packages/astro/test/before-hydration.test.js

@@ -0,0 +1,175 @@
+import { expect } from 'chai';
+import * as cheerio from 'cheerio';
+import { loadFixture } from './test-utils.js';
+import { preact } from './fixtures/before-hydration/deps.mjs';
+import testAdapter from './test-adapter.js';
+
+describe('Astro Scripts before-hydration', () => {
+	describe('SSG', () => {
+		describe('Is used by an integration', () => {
+			/** @type {import('./test-utils').Fixture} */
+			let fixture;
+	
+			before(async () => {
+				fixture = await loadFixture({
+					root: './fixtures/before-hydration/',
+					integrations: [
+						preact(),
+						{
+							name: '@test/before-hydration',
+							hooks: {
+								'astro:config:setup'({ injectScript }) {
+									injectScript('before-hydration', `import '/src/scripts/global.js';`);
+								}
+							}
+						}
+					]
+				});
+			});
+	
+			describe('Development', () => {
+				/** @type {import('./test-utils').DevServer} */
+				let devServer;
+	
+				before(async () => {
+					devServer = await fixture.startDevServer();
+				});
+	
+				after(async () => {
+					await devServer.stop();
+				});
+	
+				it('Is included in the astro-island', async () => {
+					let res = await fixture.fetch('/');
+					let html = await res.text();
+					let $ = cheerio.load(html);
+					expect($('astro-island[before-hydration-url]')).has.a.lengthOf(1);
+				});
+			});
+	
+			describe('Build', () => {
+				before(async () => {
+					await fixture.build();
+				});
+	
+				it('Is included in the astro-island', async () => {
+					let html = await fixture.readFile('/index.html')
+					let $ = cheerio.load(html);
+					expect($('astro-island[before-hydration-url]')).has.a.lengthOf(1);
+				});
+			});
+		});
+	
+		describe('Is not used by an integration', () => {
+			/** @type {import('./test-utils').Fixture} */
+			let fixture;
+	
+			before(async () => {
+				fixture = await loadFixture({
+					root: './fixtures/before-hydration/'
+				});
+			});
+	
+			describe('Development', () => {
+				/** @type {import('./test-utils').DevServer} */
+				let devServer;
+	
+				before(async () => {
+					devServer = await fixture.startDevServer();
+				});
+	
+				after(async () => {
+					await devServer.stop();
+				});
+	
+				it('Does include before-hydration-url on the astro-island', async () => {
+					let res = await fixture.fetch('/');
+					let html = await res.text();
+					let $ = cheerio.load(html);
+					expect($('astro-island[before-hydration-url]')).has.a.lengthOf(1);
+				});
+			});
+	
+			describe('Build', () => {
+				before(async () => {
+					await fixture.build();
+				});
+	
+				it('Does not include before-hydration-url on the astro-island', async () => {
+					let html = await fixture.readFile('/index.html');
+					let $ = cheerio.load(html);
+					expect($('astro-island[before-hydration-url]')).has.a.lengthOf(0);
+				});
+			});
+		});
+	});
+
+	describe('SSR', () => {
+		describe('Is used by an integration', () => {
+			/** @type {import('./test-utils').Fixture} */
+			let fixture;
+	
+			before(async () => {
+				fixture = await loadFixture({
+					root: './fixtures/before-hydration/',
+					output: 'server',
+					adapter: testAdapter(),
+					integrations: [
+						preact(),
+						{
+							name: '@test/before-hydration',
+							hooks: {
+								'astro:config:setup'({ injectScript }) {
+									injectScript('before-hydration', `import '/src/scripts/global.js';`);
+								}
+							}
+						}
+					]
+				});
+			});
+	
+			describe('Prod', () => {
+				before(async () => {
+					await fixture.build();
+				});
+	
+				it('Is included in the astro-island', async () => {
+					let app = await fixture.loadTestAdapterApp();
+					let request = new Request('http://example.com/');
+					let response = await app.render(request);
+					let html = await response.text();
+					let $ = cheerio.load(html);
+					expect($('astro-island[before-hydration-url]')).has.a.lengthOf(1);
+				});
+			});
+		});
+	
+		describe('Is not used by an integration', () => {
+			/** @type {import('./test-utils').Fixture} */
+			let fixture;
+	
+			before(async () => {
+				fixture = await loadFixture({
+					root: './fixtures/before-hydration/',
+					output: 'server',
+					adapter: testAdapter(),
+				});
+			});
+	
+			describe('Build', () => {
+				before(async () => {
+					await fixture.build();
+				});
+	
+				it('Does not include before-hydration-url on the astro-island', async () => {
+					let app = await fixture.loadTestAdapterApp();
+					let request = new Request('http://example.com/');
+					let response = await app.render(request);
+					let html = await response.text();
+					let $ = cheerio.load(html);
+					expect($('astro-island[before-hydration-url]')).has.a.lengthOf(0);
+				});
+			});
+		});
+	})
+});

packages/astro/test/fixtures/before-hydration/astro.config.mjs

@@ -0,0 +1,6 @@
+import { defineConfig } from 'astro/config';
+import preact from '@astrojs/preact';
+
+export default defineConfig({
+	integrations: [preact()]
+});

packages/astro/test/fixtures/before-hydration/deps.mjs

@@ -0,0 +1 @@
+export { default as preact } from '@astrojs/preact';

packages/astro/test/fixtures/before-hydration/package.json

@@ -0,0 +1,7 @@
+{
+  "name": "@test/before-hydration",
+  "dependencies": {
+    "astro": "workspace:*",
+    "@astrojs/preact": "workspace:*"
+  }
+}

packages/astro/test/fixtures/before-hydration/src/components/SomeComponent.jsx

@@ -0,0 +1,6 @@
+
+export default function() {
+	return (
+		<div>Testing</div>
+	);
+}

packages/astro/test/fixtures/before-hydration/src/pages/index.astro

@@ -0,0 +1,11 @@
+---
+import SomeComponent from '../components/SomeComponent';
+---
+<html>
+	<head>
+		<title>Testing</title>
+	</head>
+	<body>
+		<SomeComponent client:idle />
+	</body>
+</html>

packages/astro/test/fixtures/before-hydration/src/scripts/global.js

@@ -0,0 +1 @@
+console.log('testing');

pnpm-lock.yaml

@@ -1374,6 +1374,14 @@ importers:
     dependencies:
       astro: link:../../..
 
+  packages/astro/test/fixtures/before-hydration:
+    specifiers:
+      '@astrojs/preact': workspace:*
+      astro: workspace:*
+    dependencies:
+      '@astrojs/preact': link:../../../../integrations/preact
+      astro: link:../../..
+
   packages/astro/test/fixtures/client-address:
     specifiers:
       astro: workspace:*