fix: normalise css paths in manifest on windows (fixes #9295) (#9353)

Co-authored-by: sapphi-red <[email protected]>

packages/vite/src/node/plugins/css.ts

@@ -519,7 +519,9 @@ export function cssPostPlugin(config: ResolvedConfig): Plugin {
       }
 
       function ensureFileExt(name: string, ext: string) {
-        return path.format({ ...path.parse(name), base: undefined, ext })
+        return normalizePath(
+          path.format({ ...path.parse(name), base: undefined, ext })
+        )
       }
 
       if (config.build.cssCodeSplit) {

playground/backend-integration/__tests__/backend-integration.spec.ts

@@ -35,6 +35,7 @@ describe.runIf(isBuild)('build', () => {
     const cssAssetEntry = manifest['global.css']
     const scssAssetEntry = manifest['nested/blue.scss']
     const imgAssetEntry = manifest['../images/logo.png']
+    const dirFooAssetEntry = manifest['../../dir/foo.css'] // '\\' should not be used even on windows
     expect(htmlEntry.css.length).toEqual(1)
     expect(htmlEntry.assets.length).toEqual(1)
     expect(cssAssetEntry?.file).not.toBeUndefined()
@@ -44,6 +45,7 @@ describe.runIf(isBuild)('build', () => {
     expect(scssAssetEntry?.isEntry).toEqual(true)
     expect(imgAssetEntry?.file).not.toBeUndefined()
     expect(imgAssetEntry?.isEntry).toBeUndefined()
+    expect(dirFooAssetEntry).not.toBeUndefined()
   })
 })
 

playground/backend-integration/dir/foo.css

@@ -0,0 +1,3 @@
+.windows-path-foo {
+  color: blue;
+}

playground/backend-integration/vite.config.js

@@ -19,6 +19,7 @@ function BackendIntegrationExample() {
         .map((filename) => [path.relative(root, filename), filename])
 
       entrypoints.push(['tailwindcss-colors', 'tailwindcss/colors.js'])
+      entrypoints.push(['foo.css', path.resolve(__dirname, './dir/foo.css')])
 
       return {
         build: {