Fix periods in URLs with trailing slashes causing 404s in dev server

.changeset/fix-dotted-page-trailing-slash.md

@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Fixes pages with dots in their filenames (e.g. `hello.world.astro`) returning 404 when accessed with a trailing slash in the dev server. The `trailingSlashForPath` function now only forces `trailingSlash: 'never'` for endpoints with file extensions, allowing pages to correctly respect the user's `trailingSlash` config.

packages/astro/src/core/routing/create-manifest.ts

@@ -241,7 +241,11 @@ function createFileBasedRoutes(
 				const pathname = segments.every((segment) => segment.length === 1 && !segment[0].dynamic)
 					? `/${segments.map((segment) => segment[0].content).join('/')}`
 					: null;
-				const trailingSlash = trailingSlashForPath(pathname, settings.config);
+				const trailingSlash = trailingSlashForPath(
+					pathname,
+					settings.config,
+					item.isPage ? 'page' : 'endpoint',
+				);
 				const pattern = getPattern(segments, settings.config.base, trailingSlash);
 				const route = joinSegments(segments);
 				routes.push({
@@ -382,7 +386,11 @@ function createRoutesFromEntriesByDir(
 				const pathname = segments.every((segment) => segment.length === 1 && !segment[0].dynamic)
 					? `/${segments.map((segment) => segment[0].content).join('/')}`
 					: null;
-				const trailingSlash = trailingSlashForPath(pathname, settings.config);
+				const trailingSlash = trailingSlashForPath(
+					pathname,
+					settings.config,
+					item.isPage ? 'page' : 'endpoint',
+				);
 				const pattern = getPattern(segments, settings.config.base, trailingSlash);
 				const route = joinSegments(segments);
 				routes.push({
@@ -428,11 +436,14 @@ function groupEntriesByDir(entries: RouteEntry[]): Map<string, RouteEntry[]> {
 }
 
 // Get trailing slash rule for a path, based on the config and whether the path has an extension.
+// Only endpoints with file extensions (like /feed.xml) should force 'never' for trailing slashes.
+// Pages with dots in their names (like /hello.world) should respect the user's trailingSlash config.
 const trailingSlashForPath = (
 	pathname: string | null,
 	config: AstroConfig,
+	type: 'page' | 'endpoint',
 ): AstroConfig['trailingSlash'] =>
-	pathname && hasFileExtension(pathname) ? 'never' : config.trailingSlash;
+	type === 'endpoint' && pathname && hasFileExtension(pathname) ? 'never' : config.trailingSlash;
 
 function createInjectedRoutes({ settings, cwd }: CreateRouteManifestParams): RouteData[] {
 	const { config } = settings;
@@ -457,7 +468,7 @@ function createInjectedRoutes({ settings, cwd }: CreateRouteManifestParams): Rou
 			? `/${segments.map((segment) => segment[0].content).join('/')}`
 			: null;
 
-		const trailingSlash = trailingSlashForPath(pathname, config);
+		const trailingSlash = trailingSlashForPath(pathname, config, type);
 		const pattern = getPattern(segments, settings.config.base, trailingSlash);
 		const params = segments
 			.flat()

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

@@ -418,6 +418,67 @@ describe('routing - createRoutesList', () => {
 		]);
 	});
 
+	it('pages with dots in filenames respect trailingSlash config. issues#16140', async () => {
+		const fixture = await createFixture({
+			'/src/pages/hello.world.astro': `<h1>test</h1>`,
+			'/src/pages/feed.xml.ts': `export const GET = () => new Response('<xml />')`,
+		});
+
+		// With trailingSlash: 'ignore', page with dot should match both with and without trailing slash
+		const ignoreSettings = await createBasicSettings({
+			root: fixture.path,
+			trailingSlash: 'ignore',
+		});
+		const ignoreManifest = await createRoutesList({
+			cwd: fixture.path,
+			settings: ignoreSettings,
+		});
+		const pageRoute = ignoreManifest.routes.find((r) => r.route === '/hello.world');
+		assert.ok(pageRoute, 'page route should exist');
+		assert.equal(
+			pageRoute.pattern.test('/hello.world'),
+			true,
+			'should match without trailing slash',
+		);
+		assert.equal(pageRoute.pattern.test('/hello.world/'), true, 'should match with trailing slash');
+
+		// Endpoint with file extension should still force 'never'
+		const endpointRoute = ignoreManifest.routes.find((r) => r.route === '/feed.xml');
+		assert.ok(endpointRoute, 'endpoint route should exist');
+		assert.equal(
+			endpointRoute.pattern.test('/feed.xml'),
+			true,
+			'endpoint should match without trailing slash',
+		);
+		assert.equal(
+			endpointRoute.pattern.test('/feed.xml/'),
+			false,
+			'endpoint should not match with trailing slash',
+		);
+
+		// With trailingSlash: 'always', page with dot should only match with trailing slash
+		const alwaysSettings = await createBasicSettings({
+			root: fixture.path,
+			trailingSlash: 'always',
+		});
+		const alwaysManifest = await createRoutesList({
+			cwd: fixture.path,
+			settings: alwaysSettings,
+		});
+		const alwaysPageRoute = alwaysManifest.routes.find((r) => r.route === '/hello.world');
+		assert.ok(alwaysPageRoute, 'page route should exist with trailingSlash always');
+		assert.equal(
+			alwaysPageRoute.pattern.test('/hello.world/'),
+			true,
+			'should match with trailing slash',
+		);
+		assert.equal(
+			alwaysPageRoute.pattern.test('/hello.world'),
+			false,
+			'should not match without trailing slash',
+		);
+	});
+
 	it('should concatenate each part of the segment. issues#10122', async () => {
 		const fixture = await createFixture({
 			'/src/pages/a-[b].astro': `<h1>test</h1>`,