fix(astro): match case-mismatched project paths in normalizeFilename

.changeset/normalize-filename-case.md

@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Fixes styles being stripped when the project root is started with a path whose case differs from the actual filesystem case (e.g. running `astro dev` from `d:\dev\app` while the folder on disk is `D:\dev\app`).

packages/astro/src/vite-plugin-utils/index.ts

@@ -46,13 +46,26 @@ export function normalizeFilename(filename: string, root: URL) {
 		// is imported via a TypeScript path alias and Vite produces a relative virtual module ID.
 		const url = new URL(filename, root);
 		filename = viteID(url);
-	} else if (filename.startsWith('/') && !commonAncestorPath(filename, fileURLToPath(root))) {
+	} else if (filename.startsWith('/') && !isPathInRoot(filename, fileURLToPath(root))) {
 		const url = new URL('.' + filename, root);
 		filename = viteID(url);
 	}
 	return removeLeadingForwardSlashWindows(filename);
 }
 
+/**
+ * Check whether `filename` lives under `rootPath`. Falls back to a case-insensitive
+ * comparison so that paths whose case differs from `rootPath` (e.g. a `d:\dev\foo`
+ * cwd versus a `D:\dev\foo` filesystem on Windows, or any case-insensitive macOS
+ * volume) are still recognized as project-internal absolute paths.
+ */
+function isPathInRoot(filename: string, rootPath: string) {
+	if (commonAncestorPath(filename, rootPath)) {
+		return true;
+	}
+	return commonAncestorPath(filename.toLowerCase(), rootPath.toLowerCase()) !== '';
+}
+
 const postfixRE = /[?#].*$/s;
 export function cleanUrl(url: string): string {
 	return url.replace(postfixRE, '');

packages/astro/test/css-path-case.test.ts

@@ -0,0 +1,82 @@
+import assert from 'node:assert/strict';
+import * as fs from 'node:fs';
+import { fileURLToPath } from 'node:url';
+import { after, before, describe, it } from 'node:test';
+import * as cheerio from 'cheerio';
+import { type DevServer, type Fixture, loadFixture } from './test-utils.ts';
+
+/**
+ * Regression test for https://github.com/withastro/astro/issues/14013
+ *
+ * On case-insensitive filesystems (macOS, Windows) the dev server can be started
+ * from a project root whose case differs from the actual on-disk case (e.g.
+ * `d:\dev\app` vs `D:\dev\app`). `normalizeFilename` compares the configured
+ * `root` against Vite-resolved module ids via `commonAncestorPath`, which is
+ * case-sensitive. When the two disagree on case at the first path segment (a
+ * Windows drive letter, or the leading directory on macOS) `commonAncestorPath`
+ * returns `''`, so the absolute id is no longer recognized as project-internal
+ * and gets rewritten to a bogus path. That misses the compile-metadata cache and
+ * strips the component's scoped `<style>` from the page.
+ *
+ * To reproduce the discrepancy we flip the case of the first alphabetic
+ * character of the root path. On a case-insensitive filesystem the flipped path
+ * still resolves to the real fixture, while Vite resolves module ids with the
+ * canonical case — exactly the mismatch from the issue. On a case-sensitive
+ * filesystem (most Linux CI) the flipped path does not exist, so the suite is
+ * skipped.
+ */
+const realRoot = fileURLToPath(new URL('./fixtures/css-path-case/', import.meta.url));
+
+/** Flip the case of the first ASCII letter — the macOS leading dir or Windows drive letter. */
+function flipFirstLetterCase(p: string): string {
+	const i = p.search(/[a-zA-Z]/);
+	if (i === -1) return p;
+	const ch = p[i];
+	const flipped = ch === ch.toLowerCase() ? ch.toUpperCase() : ch.toLowerCase();
+	return p.slice(0, i) + flipped + p.slice(i + 1);
+}
+
+const caseMismatchedRoot = flipFirstLetterCase(realRoot);
+
+// Detect a case-insensitive filesystem directly rather than checking the OS:
+// the flipped-case path resolves to the real fixture only when the filesystem
+// ignores case (macOS, Windows). This is the precondition the test needs and is
+// more accurate than an OS check (macOS is case-insensitive too, and case
+// sensitivity can vary per-volume/per-directory on both macOS and Windows).
+const isCaseInsensitiveFs = caseMismatchedRoot !== realRoot && fs.existsSync(caseMismatchedRoot);
+
+describe('CSS scoped styles with a case-mismatched project root', {
+	skip: !isCaseInsensitiveFs,
+}, () => {
+	let fixture: Fixture;
+	let devServer: DevServer;
+	let $: cheerio.CheerioAPI;
+
+	before(async () => {
+		fixture = await loadFixture({ root: caseMismatchedRoot });
+		devServer = await fixture.startDevServer();
+		const html = await fixture.fetch('/').then((res) => res.text());
+		$ = cheerio.load(html);
+	});
+
+	after(async () => {
+		await devServer?.stop();
+	});
+
+	it('applies the scope to the element', () => {
+		const h1 = $('h1');
+		const scopedAttribute = Object.keys(h1[0]?.attribs ?? {}).find((key) =>
+			/^data-astro-cid-/.test(key),
+		);
+		assert.ok(scopedAttribute, 'expected the <h1> to carry a data-astro-cid-* scope attribute');
+	});
+
+	it('injects the scoped style into the page (issue #14013)', () => {
+		const injectedStyles = $('style').text().replace(/\s/g, '');
+		assert.equal(
+			injectedStyles.includes('color:rgb(255,165,0)'),
+			true,
+			'expected the scoped <style> to be injected even though the root case differs from disk',
+		);
+	});
+});

packages/astro/test/fixtures/css-path-case/package.json

@@ -0,0 +1,8 @@
+{
+  "name": "@test/css-path-case",
+  "version": "0.0.0",
+  "private": true,
+  "dependencies": {
+    "astro": "workspace:*"
+  }
+}

packages/astro/test/fixtures/css-path-case/src/pages/index.astro

@@ -0,0 +1,17 @@
+---
+---
+
+<html>
+	<head>
+		<title>Case Test</title>
+	</head>
+	<body>
+		<h1>Hello world</h1>
+	</body>
+</html>
+
+<style>
+	h1 {
+		color: rgb(255, 165, 0);
+	}
+</style>

packages/astro/test/units/vite-plugin-utils/normalize-filename.test.ts

@@ -0,0 +1,45 @@
+import * as assert from 'node:assert/strict';
+import * as path from 'node:path';
+import { describe, it } from 'node:test';
+import { pathToFileURL } from 'node:url';
+import { normalizeFilename } from '../../../dist/vite-plugin-utils/index.js';
+
+// Build a fixture path that is absolute on both POSIX and Windows. On POSIX,
+// `path.resolve('/Users/me/project')` is `/Users/me/project`; on Windows it
+// becomes something like `D:\\Users\\me\\project` (the CWD drive gets
+// prepended). Using this lets tests that pass the resolved path to Node's URL
+// machinery behave identically on both platforms.
+const projectRoot = path.resolve('/Users/me/project');
+const projectRootUrl = pathToFileURL(projectRoot + path.sep);
+// `normalizeFilename` returns paths with forward slashes (it runs the result
+// through `viteID`/`slash`), so build expectations the same way.
+const projectRootSlash = projectRoot.replaceAll(path.sep, '/');
+
+describe('normalizeFilename', () => {
+	it('strips the /@fs prefix from filesystem paths', () => {
+		const root = pathToFileURL('/Users/me/project/');
+		const result = normalizeFilename('/@fs/Users/me/project/src/pages/index.astro', root);
+		assert.equal(result, '/Users/me/project/src/pages/index.astro');
+	});
+
+	it('resolves relative paths against root', () => {
+		const result = normalizeFilename('./src/components/Foo.astro', projectRootUrl);
+		assert.equal(result, `${projectRootSlash}/src/components/Foo.astro`);
+	});
+
+	it('preserves absolute paths that live inside root', () => {
+		const root = pathToFileURL('/Users/me/project/');
+		const result = normalizeFilename('/Users/me/project/src/pages/index.astro', root);
+		assert.equal(result, '/Users/me/project/src/pages/index.astro');
+	});
+
+	it('preserves absolute paths when their case differs from root (issue #14013)', () => {
+		// Reproduces the case-insensitive filesystem scenario (Windows or macOS) where
+		// the user starts the dev server from a path whose case differs from disk.
+		// `root` comes from process.cwd() with one case, but Vite resolves modules with
+		// the canonical filesystem case. The two must still be treated as the same path.
+		const root = pathToFileURL('/users/me/project/');
+		const result = normalizeFilename('/Users/me/project/src/pages/index.astro', root);
+		assert.equal(result, '/Users/me/project/src/pages/index.astro');
+	});
+});