shouldn't resolve internalModule according to "moduleNameMapper" in jest.config.js

🐛 Bug Report

// jest.config.js
  moduleNameMapper: {
    'Utils': '<rootDir>/src/utils',
}

Runing my tests always fail, saying SyntaxError: Unexpected token 'export'. It take my a long time to try various solutions since that misleading error message (I even write a custom ts transformer) Until the end, I dived into the error stack and found that:

// requireModule method
modulePath = this._resolveModule(from, moduleName);
// from:  '/Users/justin/myproject/node_modules/expect/build/asymmetricMatchers.js'
// moduleName './jasmineUtils'
// => '/Users/justin/myproject/src/utils/index.ts' !!!!!

Expected behavior

Never use jest config when resolve internalModule

Envinfo

  System:
    OS: macOS Mojave 10.14.6
    CPU: (8) x64 Intel(R) Core(TM) i7-4770HQ CPU @ 2.20GHz
  Binaries:
    Node: 12.16.3 - /usr/local/bin/node
    Yarn: 1.22.4 - /usr/local/bin/yarn
    npm: 6.14.5 - /usr/local/bin/npm
  npmPackages:
    jest: 26.6.3 => 26.6.3 

[the-spyke]

This is definitely a bug. Another example with Lodash:

// jest.config.js
export default {
  moduleNameMapper: {
    "^lodash/": "lodash-es/",
  },
  transform: {
    "\\.(c|m)?js$": "babel-jest",
  },
  transformIgnorePatterns: [],
};

I’m replacing lodash with lodash-es same as I do in my Webpack config. Seems like Jest use Lodash on its own, but this Lodash doesn’t go through the transformer (babel-jest):

 FAIL  src/app.test.js
  ● Test suite failed to run

    Jest encountered an unexpected token

    This usually means that you are trying to import a file which Jest cannot parse, e.g. it's not plain JavaScript.

    By default, if Jest sees a Babel config, it will use that to transform your files, ignoring "node_modules".

    Here's what you can do:
     • If you are trying to use ECMAScript Modules, see https://jestjs.io/docs/en/ecmascript-modules for how to enable it.
     • To have some of your "node_modules" files transformed, you can specify a custom "transformIgnorePatterns" in your config.
     • If you need a custom transformation specify a "transform" option in your config.
     • If you simply want to mock your non-JS modules (e.g. binary assets) you can stub them out with the "moduleNameMapper" config option.

    You'll find more details and examples of these config options in the docs:
    https://jestjs.io/docs/en/configuration.html

    Details:

    /home/spyke/app/node_modules/lodash-es/lodash.js:10
    export { default as add } from './add.js';
    ^^^^^^

    SyntaxError: Unexpected token 'export'

      at Runtime.createScriptFromCode (node_modules/jest-runtime/build/index.js:1350:14)
      at Object.<anonymous> (node_modules/@babel/types/lib/builders/builder.js:8:37)

I have other packages in node_modules that are ESM and they do get transformed if I comment out Lodash. Either doesn’t run internal modules trough the mapper or apply transformers to them too. Maybe @SimenB could help to triage.

[facadesss]

@billyjov No, I didn’t.

This is definitely a bug. Another example with Lodash:

// jest.config.js
export default {
  moduleNameMapper: {
    "^lodash/": "lodash-es/",
  },
  transform: {
    "\\.(c|m)?js$": "babel-jest",
  },
  transformIgnorePatterns: [],
};

I’m replacing lodash with lodash-es same as I do in my Webpack config. Seems like Jest use Lodash on its own, but this Lodash doesn’t go through the transformer (babel-jest):

 FAIL  src/app.test.js
  ● Test suite failed to run

    Jest encountered an unexpected token

    This usually means that you are trying to import a file which Jest cannot parse, e.g. it's not plain JavaScript.

    By default, if Jest sees a Babel config, it will use that to transform your files, ignoring "node_modules".

    Here's what you can do:
     • If you are trying to use ECMAScript Modules, see https://jestjs.io/docs/en/ecmascript-modules for how to enable it.
     • To have some of your "node_modules" files transformed, you can specify a custom "transformIgnorePatterns" in your config.
     • If you need a custom transformation specify a "transform" option in your config.
     • If you simply want to mock your non-JS modules (e.g. binary assets) you can stub them out with the "moduleNameMapper" config option.

    You'll find more details and examples of these config options in the docs:
    https://jestjs.io/docs/en/configuration.html

    Details:

    /home/spyke/app/node_modules/lodash-es/lodash.js:10
    export { default as add } from './add.js';
    ^^^^^^

    SyntaxError: Unexpected token 'export'

      at Runtime.createScriptFromCode (node_modules/jest-runtime/build/index.js:1350:14)
      at Object.<anonymous> (node_modules/@babel/types/lib/builders/builder.js:8:37)

I have other packages in node_modules that are ESM and they do get transformed if I comment out Lodash. Either doesn’t run internal modules trough the mapper or apply transformers to them too. Maybe @SimenB could help to triage.

i met the same problem with lodash, have you fixed this problem?