Cannot access ... before initialization

Verify canary release

• I verified that the issue exists in the latest Next.js canary release

Provide environment information

yarn next info

    Operating System:
      Platform: darwin
      Arch: arm64
      Version: Darwin Kernel Version 21.6.0: Sat Jun 18 17:07:22 PDT 2022; root:xnu-8020.140.41~1/RELEASE_ARM64_T6000
    Binaries:
      Node: 16.16.0
      npm: 8.11.0
      Yarn: 3.2.0
      pnpm: N/A
    Relevant packages:
      next: 12.2.4
      eslint-config-next: 12.2.0
      react: 17.0.2
      react-dom: 17.0.2

warn  - Latest canary version not detected, detected: "12.2.4", newest: "12.2.6-canary.5".
        Please try the latest canary version (`npm install next@canary`) to confirm the issue still exists before creating a new issue.
        Read more - https://nextjs.org/docs/messages/opening-an-issue

What browser are you using? (if relevant)

Chrome

How are you deploying your application? (if relevant)

yarn jest

Describe the Bug

Between 12.2.0 and 12.2.1 a big chunk of our unit tests broke. Any test using jest.requireActual('') to not mock some of the modules fails with an error like this:

    ReferenceError: Cannot access 'buildError' before initialization

      81 |
    > 82 | export const buildError = {

I tried to debug this, but sadly am not able to view the swc compiled source files.

Additionally all tests using jest.mock('next/router') have to be changed to:

jest.mock('next/router', () => ({
  useRouter: jest.fn(),
});

Because that now yielded the following error:

No router instance found.
    You should only use "next/router" on the client side of your app.

Expected Behavior

jest.requireActual('') to keep working.

Link to reproduction

Tried to reproduce in simple repo but wasn’t able to get the same behaviour

To Reproduce

This part of the test that breaks:

jest.mock('./bla', () => ({
  ...jest.requireActual('./bla'),
  useBla: jest.fn(),
});

describe('SomeComponent', () => {
  const getComponent = (): ShallowWrapper => shallow(<SomeComponent />);

  it('should bla', () => {
    const component = getComponent();

    expect(component.html()).toBeNull();
  });
});

export const SomeComponent: React.FC = () => {
  const bla = useBla();

  return bla;
};

export const buildError = {
  build: () => 'test',
};

export const useBla = () => 'bla';

Compiler options:

    compiler: {
      styledComponents: {
        cssProp: false,
      },

      emotion:
        // Don't compile with jest otherwise all emotion components become EmotionCSSPropInternal
        phase === PHASE_TEST
          ? null
          : {
              sourceMap: true,
              autoLabel: 'dev-only',
              labelFormat: 'local',
            },

      removeConsole:
        phase === PHASE_PRODUCTION_BUILD || phase === PHASE_PRODUCTION_SERVER,
    },

[PepijnSenders]

@balazsorban44 any idea on this issue?

[PepijnSenders]

@balazsorban44 this release broke it: https://github.com/vercel/next.js/releases/tag/v12.2.3-canary.1. 12.2.3-canary.0 still worked.