fix(app): call renderer when routes don't match (#13483)

* fix(app): call renderer when routes don't match

* chore: pick 404 exactly

* chore: pick route differently

Co-authored-by: ascorbic <213306+ascorbic@users.noreply.github.com>

4 files changed, 30 insertions, 1 deletions

diff --git a/.changeset/wet-bottles-invite.md b/.changeset/wet-bottles-invite.md
new file mode 100644
index 000000000..629e3d318
--- /dev/null
+++ b/.changeset/wet-bottles-invite.md
@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Fixes a bug where an Astro adapter couldn't call the middleware when there isn't a route that matches the incoming request.
diff --git a/packages/astro/src/core/app/index.ts b/packages/astro/src/core/app/index.ts
index 36560478e..baf76a026 100644
--- a/packages/astro/src/core/app/index.ts
+++ b/packages/astro/src/core/app/index.ts
@@ -7,6 +7,7 @@ import {
 	REROUTE_DIRECTIVE_HEADER,
 	clientAddressSymbol,
 	responseSentSymbol,
+	DEFAULT_404_COMPONENT,
 } from '../constants.js';
 import { getSetCookiesFromResponse } from '../cookies/index.js';
 import { AstroError, AstroErrorData } from '../errors/index.js';
@@ -88,7 +89,6 @@ export class App {
 	#baseWithoutTrailingSlash: string;
 	#pipeline: AppPipeline;
 	#adapterLogger: AstroIntegrationLogger;
-	#renderOptionsDeprecationWarningShown = false;
 
 	constructor(manifest: SSRManifest, streaming = true) {
 		this.#manifest = manifest;
@@ -331,6 +331,14 @@ export class App {
 			this.#logger.debug('router', 'Astro matched the following route for ' + request.url);
 			this.#logger.debug('router', 'RouteData:\n' + routeData);
 		}
+		// At this point we haven't found a route that matches the request, so we create
+		// a "fake" 404 route, so we can call the RenderContext.render
+		// and hit the middleware, which might be able to return a correct Response.
+		if (!routeData) {
+			routeData = this.#manifestData.routes.find(
+				(route) => route.component === '404.astro' || route.component === DEFAULT_404_COMPONENT,
+			);
+		}
 		if (!routeData) {
 			this.#logger.debug('router', "Astro hasn't found routes that match " + request.url);
 			this.#logger.debug('router', "Here's the available routes:\n", this.#manifestData);
diff --git a/packages/astro/test/fixtures/middleware space/integration-middleware-post.js b/packages/astro/test/fixtures/middleware space/integration-middleware-post.js
index a4e0c90ad..cb1855d48 100644
--- a/packages/astro/test/fixtures/middleware space/integration-middleware-post.js
+++ b/packages/astro/test/fixtures/middleware space/integration-middleware-post.js
@@ -8,6 +8,10 @@ export const onRequest = defineMiddleware((context, next) => {
 			},
 		});
 	}
+	
+	if (context.url.pathname === '/does-not-exist') {
+		return context.rewrite('/rewrite');
+	}
 
 	return next();
 });
diff --git a/packages/astro/test/middleware.test.js b/packages/astro/test/middleware.test.js
index 75b965932..199128ebd 100644
--- a/packages/astro/test/middleware.test.js
+++ b/packages/astro/test/middleware.test.js
@@ -318,6 +318,18 @@ describe('Middleware API in PROD mode, SSR', () => {
 		assert.equal(response.headers.get('content-type'), 'text/html');
 	});
 
+	it('can render a page that does not exist', async () => {
+		const request = new Request('http://example.com/does-not-exist');
+		const routeData = app.match(request);
+
+		const response = await app.render(request, { routeData });
+		assert.equal(response.status, 200);
+		const html = await response.text();
+		const $ = cheerio.load(html);
+		assert.equal($('p').html(), null);
+		assert.equal($('span').html(), 'New content!!');
+	});
+
 	it('can set locals for prerendered pages to use', async () => {
 		const text = await fixture.readFile('/client/prerendered/index.html');
 		assert.equal(text.includes('<p>yes they can!</p>'), true);