Ensure mjs files are transformed with jest

packages/next/build/jest/jest.ts

@@ -100,7 +100,7 @@ export default function nextJest(options: { dir?: string } = {}) {
 
  transform: {
  // Use SWC to compile tests
- '^.+\\.(js|jsx|ts|tsx)$': [
+ '^.+\\.(js|jsx|ts|tsx|mjs)$': [
  require.resolve('../swc/jest-transformer'),
  {
  nextConfig,

packages/next/build/swc/jest-transformer.js

@@ -37,10 +37,6 @@ const isSupportEsm = 'Module' in vm
 module.exports = {
  createTransformer: (inputOptions) => ({
  process(src, filename, jestOptions) {
- if (!/\.[jt]sx?$/.test(filename)) {
- return src
- }
-
  const jestConfig = getJestConfig(jestOptions)
 
  let swcTransformOpts = getJestSWCOptions({

test/production/next/jest/index.test.ts

@@ -80,6 +80,21 @@ describe('next/jest', () => {
  });
  });
  `,
+ 'lib/hello.mjs': `
+ import path from 'path'
+
+ export default function hello() {
+ return path.join('hello', 'world')
+ }
+ `,
+ 'test/mjs-support.test.js': `
+ import path from 'path'
+ import hello from '../lib/hello.mjs'
+
+ it('should transpile .mjs file correctly', async () => {
+ expect(hello()).toBe(path.join('hello', 'world'))
+ })
+ `,
  'test/mock.test.js': `
  import router from 'next/router'
 

test/unit/jest-next-swc.test.ts

@@ -1,5 +1,4 @@
 /* eslint-env jest */
-
 describe('jest next-swc preset', () => {
  it('should have correct env', async () => {
  expect(process.env.NODE_ENV).toBe('test')