support 'export default TestEnvironment' (#8163)

* support 'export default TestEnvironment'

* Update CHANGELOG.md

CHANGELOG.md

@@ -5,6 +5,7 @@
 - `[@jest/core]` Filter API pre-filter setup hook ([#8142](https://github.com/facebook/jest/pull/8142))
 - `[jest-snapshot]` Improve report when matcher fails, part 14 ([#8132](https://github.com/facebook/jest/pull/8132))
 - `[@jest/reporter]` Display todo and skip test descriptions when verbose is true ([#8038](https://github.com/facebook/jest/pull/8038))
+- `[jest-runner]` Support default exports for test environments ([#8163](https://github.com/facebook/jest/pull/8163))
 
 ### Fixes
 

e2e/__tests__/testEnvironment.test.ts

@@ -15,5 +15,5 @@ it('respects testEnvironment docblock', () => {
   const {json: result} = runWithJson('test-environment');
 
   expect(result.success).toBe(true);
-  expect(result.numTotalTests).toBe(1);
+  expect(result.numTotalTests).toBe(2);
 });

e2e/test-environment/EsmDefaultEnvironment.js

@@ -0,0 +1,20 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates. 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';
+
+exports.__esModule = true;
+
+const NodeEnvironment = require('jest-environment-node');
+
+class Env extends NodeEnvironment {
+  constructor(...args) {
+    super(...args);
+    this.global.property = 'value';
+  }
+}
+
+exports.default = Env;

e2e/test-environment/__tests__/esmDefault.test.js

@@ -0,0 +1,13 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates. 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.
+ *
+ * @jest-environment ./EsmDefaultEnvironment.js
+ */
+'use strict';
+
+test('access env', () => {
+  expect(property).toBe('value'); // eslint-disable-line no-undef
+});

packages/jest-core/src/runGlobalHook.ts

@@ -11,11 +11,7 @@ import {addHook} from 'pirates';
 import {Config} from '@jest/types';
 import {Test} from 'jest-runner';
 import {ScriptTransformer} from '@jest/transform';
-
-// copied from https://github.com/babel/babel/blob/56044c7851d583d498f919e9546caddf8f80a72f/packages/babel-helpers/src/helpers.js#L558-L562
-function _interopRequireDefault(obj: any) {
-  return obj && obj.__esModule ? obj : {default: obj};
-}
+import {interopRequireDefault} from 'jest-util';
 
 export default async ({
   allTests,
@@ -64,7 +60,7 @@ export default async ({
         },
       );
 
-      const globalModule = _interopRequireDefault(require(modulePath)).default;
+      const globalModule = interopRequireDefault(require(modulePath)).default;
 
       if (typeof globalModule !== 'function') {
         throw new TypeError(

packages/jest-runner/src/runTest.ts

@@ -19,7 +19,7 @@ import {
 import {JestEnvironment} from '@jest/environment';
 import RuntimeClass from 'jest-runtime';
 import fs from 'graceful-fs';
-import {ErrorWithStack, setGlobal} from 'jest-util';
+import {ErrorWithStack, setGlobal, interopRequireDefault} from 'jest-util';
 import LeakDetector from 'jest-leak-detector';
 import Resolver from 'jest-resolve';
 import {getTestEnvironment} from 'jest-config';
@@ -104,7 +104,9 @@ async function runTestInternal(
     });
   }
 
-  const TestEnvironment: typeof JestEnvironment = require(testEnvironment);
+  const TestEnvironment: typeof JestEnvironment = interopRequireDefault(
+    require(testEnvironment),
+  ).default;
   const testFramework: TestFramework =
     process.env.JEST_CIRCUS === '1'
       ? require('jest-circus/runner') // eslint-disable-line import/no-extraneous-dependencies

packages/jest-util/src/index.ts

@@ -20,6 +20,7 @@ import createDirectory from './createDirectory';
 import ErrorWithStack from './ErrorWithStack';
 import getFailedSnapshotTests from './getFailedSnapshotTests';
 import installCommonGlobals from './installCommonGlobals';
+import interopRequireDefault from './interopRequireDefault';
 import isInteractive from './isInteractive';
 import isPromise from './isPromise';
 import setGlobal from './setGlobal';
@@ -46,6 +47,7 @@ export = {
   getConsoleOutput,
   getFailedSnapshotTests,
   installCommonGlobals,
+  interopRequireDefault,
   isInteractive,
   isPromise,
   pluralize,

packages/jest-util/src/interopRequireDefault.ts

@@ -0,0 +1,11 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates. 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.
+ */
+
+// copied from https://github.com/babel/babel/blob/56044c7851d583d498f919e9546caddf8f80a72f/packages/babel-helpers/src/helpers.js#L558-L562
+export default function interopRequireDefault(obj: any) {
+  return obj && obj.__esModule ? obj : {default: obj};
+}