feat: add removeJsExtension to pathsToModuleNameMapper

e2e/__tests__/native-esm-ts.test.ts

@@ -8,7 +8,7 @@ onNodeVersions('>=12.16.0', () => {
     })
 
     expect(exitCode).toBe(0)
-    expect(json.numTotalTests).toBe(3)
-    expect(json.numPassedTests).toBe(3)
+    expect(json.numTotalTests).toBe(4)
+    expect(json.numPassedTests).toBe(4)
   })
 })

e2e/native-esm-ts/__tests__/native-esm-ts.spec.ts

@@ -1,6 +1,7 @@
 import { test, expect } from '@jest/globals'
 
-import { double } from '../double'
+import { double } from '../double.js'
+import { quadruple } from '../quadruple/index.js'
 import { triple } from '../triple.mjs'
 
 test('double', () => {
@@ -11,6 +12,10 @@ test('triple', () => {
   expect(triple(2)).toBe(6)
 })
 
+test('quadruple', () => {
+  expect(quadruple(2)).toBe(8)
+})
+
 test('import.meta', () => {
   expect(typeof import.meta.url).toBe('string')
 })

e2e/native-esm-ts/jest-isolated.config.js

@@ -1,7 +1,8 @@
+import config from './jest.config.js'
+
 /** @type {import('../../dist').JestConfigWithTsJest} */
-module.exports = {
-  extensionsToTreatAsEsm: ['.ts'],
-  resolver: '<rootDir>/mjs-resolver.ts',
+export default {
+  ...config,
   transform: {
     '^.+\\.m?tsx?$': [
       '<rootDir>/../../legacy.js',

e2e/native-esm-ts/jest.config.js

@@ -0,0 +1,23 @@
+import { pathsToModuleNameMapper } from '../../dist/index.js'
+import { createRequire } from 'module'
+
+const require = createRequire(import.meta.url)
+const tsConfig = require('./tsconfig.json')
+
+/** @type {import('../../dist').JestConfigWithTsJest} */
+export default {
+  extensionsToTreatAsEsm: ['.ts'],
+  resolver: '<rootDir>/mjs-resolver.ts',
+  moduleNameMapper: pathsToModuleNameMapper(tsConfig.compilerOptions.paths, {
+    prefix: '<rootDir>',
+    useESM: true,
+  }),
+  transform: {
+    '^.+\\.m?tsx?$': [
+      '<rootDir>/../../legacy.js',
+      {
+        useESM: true,
+      },
+    ],
+  },
+}

e2e/native-esm-ts/package.json

@@ -2,14 +2,5 @@
   "type": "module",
   "devDependencies": {
     "@jest/globals": "^29.0.3"
-  },
-  "jest": {
-    "extensionsToTreatAsEsm": [".ts"],
-    "resolver": "<rootDir>/mjs-resolver.ts",
-    "transform": {
-      "^.+\\.m?tsx?$": ["<rootDir>/../../legacy.js", {
-        "useESM": true
-      }]
-    }
   }
 }

e2e/native-esm-ts/quadruple/calculate.ts

@@ -0,0 +1,2 @@
+const calculate = (x: number) => x * 4
+export default calculate

e2e/native-esm-ts/quadruple/index.ts

@@ -0,0 +1 @@
+export { default as quadruple } from '@quadruple/calculate.js'

e2e/native-esm-ts/tsconfig.json

@@ -3,6 +3,9 @@
     "module": "Node16",
     "target": "ESNext",
     "moduleResolution": "Node16",
-    "esModuleInterop": true
+    "esModuleInterop": true,
+    "paths": {
+      "@quadruple/*": ["quadruple/*"]
+    }
   }
 }

src/config/paths-to-module-name-mapper.spec.ts

@@ -39,6 +39,33 @@ describe('pathsToModuleNameMapper', () => {
     `)
   })
 
+  test('should add `js` extension to resolved config with useESM: true', () => {
+    expect(pathsToModuleNameMapper(tsconfigMap, { useESM: true })).toEqual({
+      /**
+       * Why not using snapshot here?
+       * Because the snapshot does not keep the property order, which is important for jest.
+       * A pattern ending with `\\.js` should appear before another pattern without the extension does.
+       */
+      '^log$': 'src/utils/log',
+      '^server$': 'src/server',
+      '^client$': ['src/client', 'src/client/index'],
+      '^util/(.*)\\.js$': 'src/utils/$1',
+      '^util/(.*)$': 'src/utils/$1',
+      '^api/(.*)\\.js$': 'src/api/$1',
+      '^api/(.*)$': 'src/api/$1',
+      '^test/(.*)\\.js$': 'test/$1',
+      '^test/(.*)$': 'test/$1',
+      '^mocks/(.*)\\.js$': 'test/mocks/$1',
+      '^mocks/(.*)$': 'test/mocks/$1',
+      '^test/(.*)/mock\\.js$': ['test/mocks/$1', 'test/__mocks__/$1'],
+      '^test/(.*)/mock$': ['test/mocks/$1', 'test/__mocks__/$1'],
+      '^@foo\\-bar/common$': '../common/dist/library',
+      '^@pkg/(.*)\\.js$': './packages/$1',
+      '^@pkg/(.*)$': './packages/$1',
+      '^(\\.{1,2}/.*)\\.js$': '$1',
+    })
+  })
+
   test.each(['<rootDir>/', 'foo'])('should convert tsconfig mapping with given prefix', (prefix) => {
     expect(pathsToModuleNameMapper(tsconfigMap, { prefix })).toMatchSnapshot(prefix)
   })

src/config/paths-to-module-name-mapper.ts

@@ -16,11 +16,10 @@ const logger = rootLogger.child({ [LogContexts.namespace]: 'path-mapper' })
 
 export const pathsToModuleNameMapper = (
   mapping: TsPathMapping,
-  { prefix = '' }: { prefix: string } = Object.create(null),
+  { prefix = '', useESM = false }: { prefix?: string; useESM?: boolean } = {},
 ): JestPathMapping => {
   const jestMap: JestPathMapping = {}
   for (const fromPath of Object.keys(mapping)) {
-    let pattern: string
     const toPaths = mapping[fromPath]
     // check that we have only one target path
     if (toPaths.length === 0) {
@@ -37,8 +36,8 @@ export const pathsToModuleNameMapper = (
 
         return `${enrichedPrefix}${target}`
       })
-      pattern = `^${escapeRegex(fromPath)}$`
-      jestMap[pattern] = paths.length === 1 ? paths[0] : paths
+      const cjsPattern = `^${escapeRegex(fromPath)}$`
+      jestMap[cjsPattern] = paths.length === 1 ? paths[0] : paths
     } else if (segments.length === 2) {
       const paths = toPaths.map((target) => {
         const enrichedTarget =
@@ -47,12 +46,20 @@ export const pathsToModuleNameMapper = (
 
         return `${enrichedPrefix}${enrichedTarget.replace(/\*/g, '$1')}`
       })
-      pattern = `^${escapeRegex(segments[0])}(.*)${escapeRegex(segments[1])}$`
-      jestMap[pattern] = paths.length === 1 ? paths[0] : paths
+      if (useESM) {
+        const esmPattern = `^${escapeRegex(segments[0])}(.*)${escapeRegex(segments[1])}\\.js$`
+        jestMap[esmPattern] = paths.length === 1 ? paths[0] : paths
+      }
+      const cjsPattern = `^${escapeRegex(segments[0])}(.*)${escapeRegex(segments[1])}$`
+      jestMap[cjsPattern] = paths.length === 1 ? paths[0] : paths
     } else {
       logger.warn(interpolate(Errors.NotMappingMultiStarPath, { path: fromPath }))
     }
   }
 
+  if (useESM) {
+    jestMap['^(\\.{1,2}/.*)\\.js$'] = '$1'
+  }
+
   return jestMap
 }

website/docs/getting-started/paths-mapping.md

@@ -94,3 +94,9 @@ const jestConfig: JestConfigWithTsJest = {
 
 export default jestConfig
 ```
+
+With extra options as 2nd argument:
+
+- `prefix`: append prefix to each of mapped config in the result
+- `useESM`: when using `type: module` in `package.json`, TypeScript enforces users to have explicit `js` extension when importing
+  a `ts` file. This option is to help `pathsToModuleNameMapper` to create a config to suit with this scenario.