Scope Cloudflare adapter process banner to SSR and prerender environments only

.changeset/cloudflare-client-process-banner.md

@@ -0,0 +1,5 @@
+---
+'@astrojs/cloudflare': patch
+---
+
+Fixes the `globalThis.process` shim being prepended to client-side scripts. The shim is now only added to the server output.

packages/integrations/cloudflare/src/index.ts

@@ -661,12 +661,23 @@ export default function createIntegration({
 
 					vite.build ||= {};
 					vite.build.rolldownOptions ||= {};
-					vite.build.rolldownOptions.output ||= {};
 					vite.build.rolldownOptions.external = ['sharp'];
 
+					// Scoped to the server environments: top-level `build` options are inherited by the
+					// client environment, which must not ship this shim to browsers. See https://github.com/withastro/astro/issues/18182
+					// A user-provided top-level banner takes precedence and is inherited by the server environments as-is.
 					// @ts-expect-error
-					vite.build.rolldownOptions.output.banner ||=
-						'globalThis.process ??= {}; globalThis.process.env ??= {};';
+					if (!vite.build.rolldownOptions.output?.banner) {
+						for (const name of ['ssr', 'prerender']) {
+							vite.environments ??= {};
+							const environment = (vite.environments[name] ??= {}) as Record<string, any>;
+							environment.build ??= {};
+							environment.build.rolldownOptions ??= {};
+							environment.build.rolldownOptions.output ??= {};
+							environment.build.rolldownOptions.output.banner ||=
+								'globalThis.process ??= {}; globalThis.process.env ??= {};';
+						}
+					}
 
 					// Cloudflare env is only available per request. This isn't feasible for code that access env vars
 					// in a global way, so we shim their access as `process.env.*`. This is not the recommended way for users to access environment variables. But we'll add this for compatibility for chosen variables. Mainly to support `@astrojs/db`

packages/integrations/cloudflare/test/fixtures/static/src/pages/index.astro

@@ -5,5 +5,8 @@
 <body>
 	<h1>Static Site</h1>
 	<p>This is a fully static Astro site using the Cloudflare adapter.</p>
+	<script>
+		document.querySelector("h1")?.setAttribute("data-ready", "");
+	</script>
 </body>
 </html>

packages/integrations/cloudflare/test/static.test.ts

@@ -1,20 +1,33 @@
-import { describe, it } from 'node:test';
+import { before, describe, it } from 'node:test';
 import { type Fixture, loadFixture } from './test-utils.ts';
 import assert from 'node:assert/strict';
 import { existsSync } from 'node:fs';
 import { fileURLToPath } from 'node:url';
 
 describe('Static output', () => {
 	let fixture: Fixture;
-	it('should not output a _worker.js directory for fully static sites', async () => {
+
+	before(async () => {
 		fixture = await loadFixture({
 			root: './fixtures/static',
 		});
 
 		await fixture.build();
+	});
 
+	it('should not output a _worker.js directory for fully static sites', async () => {
 		const workerExists = existsSync(fileURLToPath(new URL('_worker.js', fixture.config.outDir)));
 
 		assert.ok(!workerExists, '_worker.js directory should not exist for static sites');
 	});
+
+	it('does not prepend the process shim banner to client scripts', async () => {
+		const html = await fixture.readFile('/client/index.html');
+		assert.ok(html.includes('data-ready'), 'Expected the client script to be in the output');
+		assert.ok(!html.includes('globalThis.process'));
+		for (const file of await fixture.glob('client/_astro/*.js')) {
+			const js = await fixture.readFile('/' + file);
+			assert.ok(!js.includes('globalThis.process'), `${file} should not contain the process shim`);
+		}
+	});
 });