fix(plugins): skip virtual CSS injection for files without extracted CSS

Ensure virtual CSS is only imported when CSS is actually generated.

Author: kh4f

packages/next/src/index.ts

@@ -11,6 +11,7 @@ export const rawstyleTurboRule: Required<Required<NextConfig>['turbopack']>['rul
 
 export default function (this: { resourcePath: string }, source: string): string {
 	const { transformed, css } = transform(this.resourcePath, source)
+	if (!css) return transformed
 	const base64Css = Buffer.from(css, 'utf8').toString('base64')
 	return `import 'data:text/css;base64,${base64Css}';${transformed}`
 }

packages/vite/src/index.ts

@@ -24,6 +24,7 @@ export default (): Plugin => ({
 	transform(code, id) {
 		if (!TRANSFORMABLE_EXT.test(id)) return
 		const { transformed, css } = transform(id, code)
+		if (!css) return transformed
 		const cssId = normalizePath(id + '.css')
 		styles.set(cssId, css)
 		return `import '${VIRTUAL_PREFIX}${cssId}';${transformed}`
@@ -33,6 +34,7 @@ export default (): Plugin => ({
 		if (!TRANSFORMABLE_EXT.test(file)) return
 		const sourceCode = await read()
 		const { css } = transform(file, sourceCode)
+		if (!css) return
 		const cssId = normalizePath(file + '.css')
 		const virtualId = RESOLVED_PREFIX + cssId
 		const mod = server.moduleGraph.getModuleById(virtualId)