Fix missing CSS when 404 server Response redirects to a custom 404 page

.changeset/great-spoons-try.md

@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Fix: missing CSS import when 404 server Response redirects to a custom 404 page.

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

@@ -195,7 +195,7 @@ export class App {
 						const newRenderContext = await this.#createRenderContext(
 							url,
 							request,
-							routeData,
+							errorRouteData,
 							mod,
 							response.status
 						);

packages/astro/test/fixtures/ssr-api-route-custom-404/src/content/pages/index.md

@@ -0,0 +1,7 @@
+---
+title: Astro
+---
+
+## Index
+
+Home page

packages/astro/test/fixtures/ssr-api-route-custom-404/src/pages/404.astro

@@ -1 +1,5 @@
+---
+import "../styles/main.css"
+---
+
 <h1>Something went horribly wrong!</h1>

packages/astro/test/fixtures/ssr-api-route-custom-404/src/pages/blog/[...ssrPath].astro

@@ -0,0 +1,9 @@
+---
+import { getEntry } from 'astro:content';
+const { ssrPath } = Astro.params;
+const page = await getEntry('pages', ssrPath === undefined ? 'index' : ssrPath);
+if (!page) return new Response(null, {
+  status: 404,
+  statusText: 'Not found'
+});
+---

packages/astro/test/fixtures/ssr-api-route-custom-404/src/styles/main.css

@@ -0,0 +1,3 @@
+h1 {
+    color: red;
+}

packages/astro/test/ssr-404-500-pages.test.js

@@ -62,6 +62,17 @@ describe('404 and 500 pages', () => {
 			expect($('h1').text()).to.equal('Something went horribly wrong!');
 		});
 
+		it('404 page returned when a route does not match and imports are included', async () => {
+			const app = await fixture.loadTestAdapterApp();
+			const request = new Request('http://example.com/blog/fake/route');
+			const routeData = app.match(request);
+			const response = await app.render(request, routeData);
+			expect(response.status).to.equal(404);
+			const html = await response.text();
+			const $ = cheerio.load(html);
+			expect($('head link')).to.have.a.lengthOf(1);
+		});
+
 		it('404 page returned when there is an 404 response returned from route', async () => {
 			const app = await fixture.loadTestAdapterApp();
 			const request = new Request('http://example.com/causes-404');