fix: ensure the index route matches with base and no trailing slash

.changeset/full-cloths-sleep.md

@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Fixes a bug that caused index pages to not be found when a `base` was set with `trailingSlash: never`

packages/astro/src/core/routing/manifest/pattern.ts

@@ -38,7 +38,7 @@ export function getPattern(
 	const trailing =
 		addTrailingSlash && segments.length ? getTrailingSlashPattern(addTrailingSlash) : '$';
 	let initial = '\\/';
-	if (addTrailingSlash === 'never' && base !== '/') {
+	if (addTrailingSlash === 'never' && base !== '/' && pathname !== '') {
 		initial = '';
 	}
 	return new RegExp(`^${pathname || initial}${trailing}`);

packages/astro/src/vite-plugin-astro-server/base.ts

@@ -30,6 +30,7 @@ export function baseMiddleware(
 
 		if (pathname.startsWith(devRoot)) {
 			req.url = url.replace(devRoot, devRootReplacement);
+			req.url ||= '/';
 			return next();
 		}
 

packages/astro/test/ssr-trailing-slash.test.js

@@ -255,9 +255,7 @@ describe('Redirecting trailing slashes in SSR', () => {
 			const app = await fixture.loadTestAdapterApp();
 			const request = new Request('http://example.com/mybase');
 			const response = await app.render(request);
-			// Should not redirect, but will 404 since we don't have an index page
-			assert.notEqual(response.status, 301);
-			assert.notEqual(response.status, 308);
+			assert.equal(response.status, 200);
 		});
 
 		it('Redirects to remove trailing slash on sub-paths with base', async () => {

packages/astro/test/units/routing/manifest.test.js

@@ -37,7 +37,7 @@ function assertRouteRelations(routes, relations) {
 }
 
 describe('routing - createRoutesList', () => {
-	it('using trailingSlash: "never" does not match the index route when it contains a trailing slash', async () => {
+	it('using trailingSlash: "never" matches the index route when it contains a trailing slash', async () => {
 		const fixture = await createFixture({
 			'/src/pages/index.astro': `<h1>test</h1>`,
 		});
@@ -51,8 +51,9 @@ describe('routing - createRoutesList', () => {
 			settings,
 		});
 		const [{ pattern }] = manifest.routes;
-		assert.equal(pattern.test(''), true);
-		assert.equal(pattern.test('/'), false);
+		// Requesting `/` *should* match the index route, because that's what it sees when requesting `/search`.
+		// If they've requested `/search/` this will have been caught by trailingSlashMiddleware
+		assert.equal(pattern.test('/'), true);
 	});
 
 	it('endpoint routes are sorted before page routes', async () => {