feat: export babel-preset-jest as a function

CHANGELOG.md

@@ -45,6 +45,7 @@
 - `[jest-runtime]` Fix missing coverage when using negative glob pattern in `testMatch` ([#7170](https://github.com/facebook/jest/pull/7170))
 - `[*]` Ensure `maxWorkers` is at least 1 (was 0 in some cases where there was only 1 CPU) ([#7182](https://github.com/facebook/jest/pull/7182))
 - `[jest-runtime]` Fix transform cache invalidation when requiring a test file from multiple projects ([#7186](https://github.com/facebook/jest/pull/7186))
+- `[babel-preset-jest]` [**BREAKING**] Export a function instead of an object for Babel 7 compatibility ([#7203](https://github.com/facebook/jest/pull/7203))
 
 ### Chore & Maintenance
 

e2e/coverage-transform-instrumented/Preprocessor.js

@@ -5,9 +5,9 @@
  * LICENSE file in the root directory of this source tree.
  */
 
-const jestPreset = require('babel-preset-jest');
 const {transform: babelTransform} = require('babel-core');
 const {default: babelIstanbulPlugin} = require('babel-plugin-istanbul');
+const jestPreset = require.resolve('babel-preset-jest');
 
 const options = {
   presets: ['env', jestPreset],

packages/babel-jest/src/index.js

@@ -18,7 +18,6 @@ import type {
 import crypto from 'crypto';
 import fs from 'fs';
 import path from 'path';
-import jestPreset from 'babel-preset-jest';
 import {transform as babelTransform, util as babelUtil} from 'babel-core';
 import babelIstanbulPlugin from 'babel-plugin-istanbul';
 
@@ -28,6 +27,7 @@ const BABEL_CONFIG_JS_FILENAME = 'babel.config.js';
 const BABEL_CONFIG_KEY = 'babel';
 const PACKAGE_JSON = 'package.json';
 const THIS_FILE = fs.readFileSync(__filename);
+const jestPresetPath = require.resolve('babel-preset-jest');
 
 const createTransformer = (options: any): Transformer => {
   const cache = Object.create(null);
@@ -81,7 +81,7 @@ const createTransformer = (options: any): Transformer => {
   options = Object.assign({}, options, {
     compact: false,
     plugins: (options && options.plugins) || [],
-    presets: ((options && options.presets) || []).concat([jestPreset]),
+    presets: ((options && options.presets) || []).concat(jestPresetPath),
     sourceMaps: 'both',
   });
   delete options.cacheDirectory;

packages/babel-preset-jest/index.js

@@ -5,10 +5,9 @@
  * LICENSE file in the root directory of this source tree.
  */
 
-module.exports = {
+module.exports = () => ({
   plugins: [
-    // Cannot be `import` as this file is not compiled
-    require('babel-plugin-jest-hoist'),
-    require('babel-plugin-syntax-object-rest-spread'),
+    require.resolve('babel-plugin-jest-hoist'),
+    require.resolve('babel-plugin-syntax-object-rest-spread'),
   ],
-};
+});