fix: eliminate race in compilation cache (#26353)

Fixes #24569

Author: aslushnikov

packages/playwright-core/src/utils/fileUtils.ts

@@ -15,8 +15,10 @@
  */
 
 import fs from 'fs';
+import type { WriteFileOptions } from 'fs';
 import path from 'path';
 import { rimraf } from '../utilsBundle';
+import { createGuid } from './crypto';
 
 export const existsAsync = (path: string): Promise<boolean> => new Promise(resolve => fs.stat(path, err => resolve(!err)));
 
@@ -53,3 +55,11 @@ export async function copyFileAndMakeWritable(from: string, to: string) {
 export function sanitizeForFilePath(s: string) {
   return s.replace(/[\x00-\x2C\x2E-\x2F\x3A-\x40\x5B-\x60\x7B-\x7F]+/g, '-');
 }
+
+export function writeFileSyncAtomic(aPath: string, data: Buffer | string, options: WriteFileOptions) {
+  const dirName = path.dirname(aPath);
+  const fileName = path.basename(aPath);
+  const tmpPath = path.join(dirName, fileName + '-' + createGuid());
+  fs.writeFileSync(tmpPath, data, options);
+  fs.renameSync(tmpPath, aPath);
+}

packages/playwright-test/src/transform/compilationCache.ts

@@ -18,6 +18,7 @@ import fs from 'fs';
 import os from 'os';
 import path from 'path';
 import { sourceMapSupport } from '../utilsBundle';
+import { writeFileSyncAtomic } from 'playwright-core/lib/utils';
 
 export type MemoryCache = {
   codePath: string;
@@ -85,8 +86,8 @@ export function getFromCompilationCache(filename: string, hash: string, moduleUr
     addToCache: (code: string, map: any) => {
       fs.mkdirSync(path.dirname(cachePath), { recursive: true });
       if (map)
-        fs.writeFileSync(sourceMapPath, JSON.stringify(map), 'utf8');
-      fs.writeFileSync(codePath, code, 'utf8');
+        writeFileSyncAtomic(sourceMapPath, JSON.stringify(map), 'utf8');
+      writeFileSyncAtomic(codePath, code, 'utf8');
       _innerAddToCompilationCache(filename, { codePath, sourceMapPath, moduleUrl });
     }
   };

packages/playwright-test/src/transform/transform.ts

@@ -166,7 +166,7 @@ export function transformHook(originalCode: string, filename: string, moduleUrl?
   const pluginsEpilogue = hasPreprocessor ? [[process.env.PW_TEST_SOURCE_TRANSFORM!]] as BabelPlugin[] : [];
   const hash = calculateHash(originalCode, filename, !!moduleUrl, pluginsPrologue, pluginsEpilogue);
   const { cachedCode, addToCache } = getFromCompilationCache(filename, hash, moduleUrl);
-  if (cachedCode)
+  if (cachedCode !== undefined)
     return cachedCode;
 
   // We don't use any browserslist data, but babel checks it anyway.