fix(css): css file emit synchronously

package.json

@@ -79,7 +79,7 @@
     "prompts": "^2.4.2",
     "resolve": "^1.22.1",
     "rimraf": "^4.4.0",
-    "rollup": "^3.20.0",
+    "rollup": "^3.20.2",
     "semver": "^7.3.8",
     "simple-git-hooks": "^2.8.1",
     "tslib": "^2.5.0",

packages/vite/package.json

@@ -69,7 +69,7 @@
     "esbuild": "^0.17.5",
     "postcss": "^8.4.21",
     "resolve": "^1.22.1",
-    "rollup": "^3.20.0"
+    "rollup": "^3.20.2"
   },
   "optionalDependencies": {
     "fsevents": "~2.3.2"

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

@@ -316,6 +316,8 @@ export function cssPlugin(config: ResolvedConfig): Plugin {
 export function cssPostPlugin(config: ResolvedConfig): Plugin {
   // styles initialization in buildStart causes a styling loss in watch
   const styles: Map<string, string> = new Map<string, string>()
+  // list of css emit tasks to guarantee the files are emitted in a deterministic order
+  let emitTasks: Promise<void>[] = []
   let pureCssChunks: Set<RenderedChunk>
 
   // when there are multiple rollup outputs and extracting CSS, only emit once,
@@ -353,6 +355,7 @@ export function cssPostPlugin(config: ResolvedConfig): Plugin {
       pureCssChunks = new Set<RenderedChunk>()
       outputToExtractedCSSMap = new Map<NormalizedOutputOptions, string>()
       hasEmitted = false
+      emitTasks = []
     },
 
     async transform(css, id, options) {
@@ -563,7 +566,22 @@ export function cssPostPlugin(config: ResolvedConfig): Plugin {
           const cssFileName = ensureFileExt(cssAssetName, '.css')
 
           chunkCSS = resolveAssetUrlsInCss(chunkCSS, cssAssetName)
-          chunkCSS = await finalizeCss(chunkCSS, true, config)
+
+          const previousTask = emitTasks[emitTasks.length - 1]
+          // finalizeCss is async which makes `emitFile` non-deterministic, so
+          // we use a `.then` to wait for previous tasks before finishing this
+          const thisTask = finalizeCss(chunkCSS, true, config).then((css) => {
+            chunkCSS = css
+            // make sure the previous task is also finished, this works recursively
+            return previousTask
+          })
+
+          // push this task so the next task can wait for this one
+          emitTasks.push(thisTask)
+          const emitTasksLength = emitTasks.length
+
+          // wait for this and previous tasks to finish
+          await thisTask
 
           // emit corresponding css file
           const referenceId = this.emitFile({
@@ -577,6 +595,11 @@ export function cssPostPlugin(config: ResolvedConfig): Plugin {
             .get(config)!
             .set(referenceId, { originalName, isEntry })
           chunk.viteMetadata!.importedCss.add(this.getFileName(referenceId))
+
+          if (emitTasksLength === emitTasks.length) {
+            // this is the last task, clear `emitTasks` to free up memory
+            emitTasks = []
+          }
         } else if (!config.build.ssr) {
           // legacy build and inline css