fix script_transformer test

packages/jest-runtime/src/__tests__/script_transformer.test.js

@@ -9,9 +9,11 @@
  */
 'use strict';
 
+const crypto = require('crypto');
 const slash = require('slash');
 
 jest
+  .mock('fs')
   .mock('graceful-fs')
   .mock('jest-haste-map', () => ({
     getCacheFilePath: (cacheDir, baseDir, version) => cacheDir + baseDir,
@@ -100,6 +102,14 @@ let fs;
 let mockFs;
 let object;
 let vm;
+let writeFileAtomic;
+
+jest.mock('write-file-atomic', () => ({
+  sync: jest.fn().mockImplementation((filePath, data) => {
+    const normalizedPath = require('slash')(filePath);
+    mockFs[normalizedPath] = data;
+  }),
+}));
 
 describe('ScriptTransformer', () => {
   const reset = () => {
@@ -145,6 +155,8 @@ describe('ScriptTransformer', () => {
 
     fs.existsSync = jest.fn(path => !!mockFs[path]);
 
+    writeFileAtomic = require('write-file-atomic');
+
     config = {
       cache: true,
       cacheDirectory: '/cache/',
@@ -290,10 +302,13 @@ describe('ScriptTransformer', () => {
       mapCoverage: true,
     });
     expect(result.sourceMapPath).toEqual(expect.any(String));
-    expect(fs.writeFileSync).toBeCalledWith(
+    const mapStr = JSON.stringify(map);
+    expect(
+      writeFileAtomic.sync,
+    ).toBeCalledWith(
       result.sourceMapPath,
-      JSON.stringify(map),
-      'utf8',
+      crypto.createHash('md5').update(mapStr).digest('hex') + mapStr,
+      {encoding: 'utf8'},
     );
   });
 
@@ -320,10 +335,12 @@ describe('ScriptTransformer', () => {
       mapCoverage: true,
     });
     expect(result.sourceMapPath).toEqual(expect.any(String));
-    expect(fs.writeFileSync).toBeCalledWith(
+    expect(
+      writeFileAtomic.sync,
+    ).toBeCalledWith(
       result.sourceMapPath,
-      sourceMap,
-      'utf8',
+      crypto.createHash('md5').update(sourceMap).digest('hex') + sourceMap,
+      {encoding: 'utf8'},
     );
   });
 
@@ -348,7 +365,7 @@ describe('ScriptTransformer', () => {
       mapCoverage: false,
     });
     expect(result.sourceMapPath).toBeFalsy();
-    expect(fs.writeFileSync).toHaveBeenCalledTimes(1);
+    expect(writeFileAtomic.sync).toHaveBeenCalledTimes(1);
   });
 
   it('reads values from the cache', () => {
@@ -359,8 +376,8 @@ describe('ScriptTransformer', () => {
     scriptTransformer.transform('/fruits/banana.js', {});
 
     const cachePath = getCachePath(mockFs, config);
-    expect(fs.writeFileSync).toBeCalled();
-    expect(fs.writeFileSync.mock.calls[0][0]).toBe(cachePath);
+    expect(writeFileAtomic.sync).toBeCalled();
+    expect(writeFileAtomic.sync.mock.calls[0][0]).toBe(cachePath);
 
     // Cache the state in `mockFsCopy`
     const mockFsCopy = mockFs;
@@ -375,7 +392,7 @@ describe('ScriptTransformer', () => {
     expect(fs.readFileSync.mock.calls.length).toBe(2);
     expect(fs.readFileSync).toBeCalledWith('/fruits/banana.js', 'utf8');
     expect(fs.readFileSync).toBeCalledWith(cachePath, 'utf8');
-    expect(fs.writeFileSync).not.toBeCalled();
+    expect(writeFileAtomic.sync).not.toBeCalled();
 
     // Don't read from the cache when `config.cache` is false.
     jest.resetModuleRegistry();
@@ -388,6 +405,6 @@ describe('ScriptTransformer', () => {
     expect(fs.readFileSync.mock.calls.length).toBe(1);
     expect(fs.readFileSync).toBeCalledWith('/fruits/banana.js', 'utf8');
     expect(fs.readFileSync).not.toBeCalledWith(cachePath, 'utf8');
-    expect(fs.writeFileSync).toBeCalled();
+    expect(writeFileAtomic.sync).toBeCalled();
   });
 });

packages/jest-runtime/src/script_transformer.js

@@ -191,6 +191,10 @@ class ScriptTransformer {
       : null;
 
     if (code) {
+      // This is broken: we return the code, and a path for the source map
+      // directly from the cache. But, nothing ensures the source map actually
+      // matches that source code. They could have gotten out-of-sync in case
+      // two separate processes write concurrently to the same cache files.
       return {
         code,
         sourceMapPath,
@@ -385,8 +389,11 @@ const readCacheFile = (filename: Path, cachePath: Path): ?string => {
       return null;
     }
   } catch (e) {
-    e.message = 'jest: failed to read cache file: ' + cachePath +
-      '\nFailure message: ' + e.message;
+    e.message =
+      'jest: failed to read cache file: ' +
+      cachePath +
+      '\nFailure message: ' +
+      e.message;
     removeFile(cachePath);
     throw e;
   }