fix: support Babel config file with .cjs extension (#3361)

Closes #3335

e2e/transform-js/babel-cjs-file/jest.config.js

@@ -0,0 +1,18 @@
+/** @type {import('../../../dist').InitialOptionsTsJest} */
+module.exports = {
+  displayName: 'babel-cjs-file',
+  roots: ['<rootDir>', '<rootDir>/../__tests__/for-babel'],
+  globals: {
+    'ts-jest': {
+      babelConfig: '<rootDir>/babel.config.cjs',
+      isolatedModules: true,
+    },
+  },
+  moduleNameMapper: {
+    '@babel/core': '<rootDir>/../../../node_modules/@babel/core',
+    'babel-jest': '<rootDir>/../../../node_modules/babel-jest',
+  },
+  transform: {
+    '^.+.[tj]sx?$': '<rootDir>/../../../dist/index.js',
+  },
+}

e2e/transform-js/babel-js-file/babel.config.js

@@ -0,0 +1,3 @@
+module.exports = {
+  presets: ['@babel/preset-env'],
+}

e2e/transform-js/babel-file/jest.config.js → e2e/transform-js/babel-js-file/jest.config.js

@@ -1,6 +1,6 @@
 /** @type {import('../../../dist').InitialOptionsTsJest} */
 module.exports = {
-  displayName: 'babel-file',
+  displayName: 'babel-js-file',
   roots: ['<rootDir>', '<rootDir>/../__tests__/for-babel'],
   globals: {
     'ts-jest': {

e2e/transform-js/babel-js-file/tsconfig.json

@@ -0,0 +1,6 @@
+{
+  "extends": "../tsconfig.json",
+  "compilerOptions": {
+    "module": "ESNext"
+  }
+}

e2e/transform-js/jest-babel.config.js

@@ -1,3 +1,3 @@
 module.exports = {
-  projects: ['babel-enabled', 'babel-file'],
+  projects: ['babel-enabled', 'babel-js-file', 'babel-cjs-file'],
 }

src/__mocks__/babel-foo.config.cjs

@@ -0,0 +1,3 @@
+module.exports = {
+  presets: ['@babel/preset-env', '@babel/preset-typescript', '@babel/preset-react'],
+}

src/config/config-set.spec.ts

@@ -275,35 +275,37 @@ describe('babelJestTransformer', () => {
     expect(typeof babelJest.process).toBe('function')
   })
 
-  it('should return babelJestTransformer with javascript file path', () => {
-    const FILE = 'src/__mocks__/babel-foo.config.js'
-    const cs = createConfigSet({
-      jestConfig: {
-        globals: {
-          'ts-jest': {
-            babelConfig: FILE,
+  it.each(['src/__mocks__/babel-foo.config.js', 'src/__mocks__/babel-foo.config.cjs'])(
+    'should return babelJestTransformer with javascript file path',
+    (babelFilePath) => {
+      const cs = createConfigSet({
+        jestConfig: {
+          globals: {
+            'ts-jest': {
+              babelConfig: babelFilePath,
+            },
           },
         },
-      },
-      resolve: null,
-    })
-    const babelJest = cs.babelJestTransformer as Transformer
+        resolve: null,
+      })
+      const babelJest = cs.babelJestTransformer as Transformer
 
-    // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
-    const babelCfg = cs.babelConfig!
-    expect(babelCfg.cwd).toEqual(cs.cwd)
-    expect(babelCfg.presets).toMatchInlineSnapshot(`
+      // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+      const babelCfg = cs.babelConfig!
+      expect(babelCfg.cwd).toEqual(cs.cwd)
+      expect(babelCfg.presets).toMatchInlineSnapshot(`
       Array [
         "@babel/preset-env",
         "@babel/preset-typescript",
         "@babel/preset-react",
       ]
     `)
-    expect(babelJest.canInstrument).toBe(true)
-    expect(babelJest.createTransformer).toBeUndefined()
-    expect(typeof babelJest.getCacheKey).toBe('function')
-    expect(typeof babelJest.process).toBe('function')
-  })
+      expect(babelJest.canInstrument).toBe(true)
+      expect(babelJest.createTransformer).toBeUndefined()
+      expect(typeof babelJest.getCacheKey).toBe('function')
+      expect(typeof babelJest.process).toBe('function')
+    },
+  )
 
   it('should return babelJestTransformer with loaded config object', () => {
     /* eslint-disable-next-line jest/no-mocks-import */

src/config/config-set.ts

@@ -242,7 +242,8 @@ export class ConfigSet {
       const baseBabelCfg = { cwd: this.cwd }
       if (typeof options.babelConfig === 'string') {
         const babelCfgPath = this.resolvePath(options.babelConfig)
-        if (extname(options.babelConfig) === '.js') {
+        const babelFileExtName = extname(options.babelConfig)
+        if (babelFileExtName === '.js' || babelFileExtName === '.cjs') {
           this.babelConfig = {
             ...baseBabelCfg,
             ...require(babelCfgPath),