moduleFileExtensions extensions is now passed to babel-jest (#5110)

* moduleFileExtensions extensions is now passed to babel-jest

* Added test to show use of custom files extensions with babel-jest

CHANGELOG: moduleFileExtensions now passed to babel transformer

* Cleanup

Cleaned integration_tests/transform/ecmascript-modules-support/yarn.lock
Cleaned integration_tests/transform/ecmascript-modules-support/package.json
Enable testing on windows

* Remove yarn lock

* Add changelog line

CHANGELOG.md

@@ -4,6 +4,9 @@ None for now
 
 ### Fixes
 
+* `[babel-jest]` moduleFileExtensions not passed to babel transformer.
+  ([#4637](https://github.com/facebook/jest/issues/4637))
+
 ### Features
 
 ### Chore & Maintenance

integration_tests/__tests__/transform.test.js

@@ -120,3 +120,18 @@ describe('multiple-transformers', () => {
     expect(json.numPassedTests).toBe(1);
   });
 });
+
+describe('ecmascript-modules-support', () => {
+  const dir = path.resolve(
+    __dirname,
+    '..',
+    'transform/ecmascript-modules-support',
+  );
+
+  it('runs transpiled code', () => {
+    // --no-cache because babel can cache stuff and result in false green
+    const {json} = runJest.json(dir, ['--no-cache']);
+    expect(json.success).toBe(true);
+    expect(json.numTotalTests).toBeGreaterThanOrEqual(1);
+  });
+});

integration_tests/transform/ecmascript-modules-support/.babelrc

@@ -0,0 +1,10 @@
+{
+  "presets": [
+    ["env", {
+      "targets": {
+        "node": "current"
+      },
+      "modules": "commonjs"
+    }]
+  ]
+}

integration_tests/transform/ecmascript-modules-support/__tests__/ecmascript-modules-support.mjs

@@ -0,0 +1,13 @@
+/**
+ * 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';
+
+import {foo} from '../src/module';
+
+it('can be used with mjs files using babel-jest', () => {
+  expect(foo()).toBe('a');
+});

integration_tests/transform/ecmascript-modules-support/package.json

@@ -0,0 +1,10 @@
+{
+  "jest": {
+    "testEnvironment": "node",
+    "moduleFileExtensions": ["js", "json", "jsx", "node", "mjs"],
+    "testMatch": [ "**/__tests__/**/*.mjs"],
+    "transform": {
+      "^.+\\.mjs?$": "../../../packages/babel-jest"
+    }
+  }
+}

integration_tests/transform/ecmascript-modules-support/src/index.mjs

@@ -0,0 +1,3 @@
+import {foo} from './module';
+
+foo();

integration_tests/transform/ecmascript-modules-support/src/module.mjs

@@ -0,0 +1 @@
+export const foo = () => 'a';

packages/babel-jest/src/index.js

@@ -104,7 +104,10 @@ const createTransformer = (options: any) => {
       config: ProjectConfig,
       transformOptions: TransformOptions,
     ): string {
-      if (babelUtil && !babelUtil.canCompile(filename)) {
+      const altExts = config.moduleFileExtensions.map(
+        extension => '.' + extension,
+      );
+      if (babelUtil && !babelUtil.canCompile(filename, altExts)) {
         return src;
       }