fix(manifest): non entry CSS chunk src was wrong (#18133)

docs/guide/backend-integration.md

@@ -61,15 +61,15 @@ If you need a custom integration, you can follow the steps in this guide to conf
 
    ```json [.vite/manifest.json]
    {
-     "_shared-!~{003}~.js": {
-       "file": "assets/shared-ChJ_j-JJ.css",
-       "src": "_shared-!~{003}~.js"
-     },
      "_shared-B7PI925R.js": {
        "file": "assets/shared-B7PI925R.js",
        "name": "shared",
        "css": ["assets/shared-ChJ_j-JJ.css"]
      },
+     "_shared-ChJ_j-JJ.css": {
+       "file": "assets/shared-ChJ_j-JJ.css",
+       "src": "_shared-ChJ_j-JJ.css"
+     },
      "baz.js": {
        "file": "assets/baz-B2H3sXNv.js",
        "name": "baz",

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

@@ -57,7 +57,10 @@ export function manifestPlugin(): Plugin {
       const buildOptions = this.environment.config.build
 
       function getChunkName(chunk: OutputChunk) {
-        return getChunkOriginalFileName(chunk, root, format)
+        return (
+          getChunkOriginalFileName(chunk, root, format) ??
+          `_` + path.basename(chunk.fileName)
+        )
       }
 
       function getInternalImports(imports: string[]): string[] {
@@ -150,7 +153,7 @@ export function manifestPlugin(): Plugin {
           const src =
             chunk.originalFileNames.length > 0
               ? chunk.originalFileNames[0]
-              : chunk.names[0]
+              : '_' + path.basename(chunk.fileName)
           const isEntry = entryCssAssetFileNames.has(chunk.fileName)
           const asset = createAsset(chunk, src, isEntry)
 
@@ -189,7 +192,7 @@ export function getChunkOriginalFileName(
   chunk: OutputChunk | RenderedChunk,
   root: string,
   format: InternalModuleFormat,
-): string {
+): string | undefined {
   if (chunk.facadeModuleId) {
     let name = normalizePath(path.relative(root, chunk.facadeModuleId))
     if (format === 'system' && !chunk.name.includes('-legacy')) {
@@ -198,7 +201,5 @@ export function getChunkOriginalFileName(
       name = name.slice(0, endPos) + `-legacy` + ext
     }
     return name.replace(/\0/g, '')
-  } else {
-    return `_` + path.basename(chunk.fileName)
   }
 }