fix: set cwd in babel-jest (jestjs#7574)

CHANGELOG.md

@@ -103,6 +103,7 @@
 - `[pretty-format]` Omit unnecessary symbol filter for object keys ([#7457](https://github.com/facebook/jest/pull/7457))
 - `[jest-runtime]` Fix `requireActual` on node_modules with mock present ([#7404](https://github.com/facebook/jest/pull/7404))
 - `[jest-resolve]` Fix `isBuiltinModule` to support versions of node without `module.builtinModules` ([#7565](https://github.com/facebook/jest/pull/7565))
+- `[babel-jest]` Set `cwd` to be resilient to it changing during the runtime of the tests ([#7574](https://github.com/facebook/jest/pull/7574))
 
 ### Chore & Maintenance
 

e2e/__tests__/transform.test.js

@@ -29,7 +29,7 @@ describe('babel-jest', () => {
     // --no-cache because babel can cache stuff and result in false green
     const {json} = runWithJson(dir, ['--no-cache']);
     expect(json.success).toBe(true);
-    expect(json.numTotalTests).toBeGreaterThanOrEqual(1);
+    expect(json.numTotalTests).toBeGreaterThanOrEqual(2);
   });
 
   it('instruments only specific files and collects coverage', () => {

e2e/transform/babel-jest/__tests__/changed_cwd.test.js

@@ -0,0 +1,22 @@
+/**
+ * Copyright (c) 2014-present, Facebook, Inc. All rights reserved.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+'use strict';
+
+const path = require('path');
+
+beforeAll(() => {
+  process.chdir(path.resolve(__dirname, '../some-dir'));
+
+  // even though we change the cwd, correct config is still found
+  require('../this-directory-is-covered/ExcludedFromCoverage');
+});
+
+it('strips flowtypes using babel-jest and .babelrc', () => {
+  const a: string = 'a';
+  expect(a).toBe('a');
+});

packages/babel-jest/src/index.js

@@ -19,13 +19,19 @@ import crypto from 'crypto';
 import fs from 'fs';
 import path from 'path';
 import {transformSync as babelTransform, loadPartialConfig} from '@babel/core';
-import babelIstanbulPlugin from 'babel-plugin-istanbul';
 
 const THIS_FILE = fs.readFileSync(__filename);
 const jestPresetPath = require.resolve('babel-preset-jest');
+const babelIstanbulPlugin = require.resolve('babel-plugin-istanbul');
+const cwd = process.cwd();
 
 export const createTransformer = (options: any): Transformer => {
-  options = Object.assign({}, options, {
+  // Allow incoming options to override `cwd`
+  options = Object.assign({cwd}, options, {
+    caller: {
+      name: 'babel-jest',
+      supportsStaticESM: false,
+    },
     compact: false,
     plugins: (options && options.plugins) || [],
     presets: ((options && options.presets) || []).concat(jestPresetPath),
@@ -35,16 +41,6 @@ export const createTransformer = (options: any): Transformer => {
   delete options.cacheDirectory;
   delete options.filename;
 
-  const loadBabelOptions = filename =>
-    loadPartialConfig({
-      ...options,
-      caller: {
-        name: 'babel-jest',
-        supportsStaticESM: false,
-      },
-      filename,
-    });
-
   return {
     canInstrument: true,
     getCacheKey(
@@ -53,7 +49,7 @@ export const createTransformer = (options: any): Transformer => {
       configString: string,
       {instrument, rootDir}: CacheKeyOptions,
     ): string {
-      const babelOptions = loadBabelOptions(filename);
+      const babelOptions = loadPartialConfig({...options, filename});
       const configPath = [
         babelOptions.config || '',
         babelOptions.babelrc || '',
@@ -86,7 +82,9 @@ export const createTransformer = (options: any): Transformer => {
       config: ProjectConfig,
       transformOptions?: TransformOptions,
     ): string | TransformedSource {
-      const babelOptions = {...loadBabelOptions(filename).options};
+      const babelOptions = {
+        ...loadPartialConfig({...options, filename}).options,
+      };
 
       if (transformOptions && transformOptions.instrument) {
         babelOptions.auxiliaryCommentBefore = ' istanbul ignore next ';