Incorrect ESM config loading in 25.5.2

[aldeed]

🐛 Bug Report

In a new project using Jest 25.5.2 and Node 12.16.0, using a Jest config file that is an ES module results in an error: TypeError [ERR_VM_DYNAMIC_IMPORT_CALLBACK_MISSING]: A dynamic import callback was not specified.

To Reproduce

https://github.com/aldeed/jest-esm-config-issue#how-to-run-and-see-error

Expected behavior

1. Whether it has .mjs extension or nearest package.json has type: "module", the config file should be loaded identically as an ES module, and there should not be errors.
2. Because of the above expectation, jest --init command should detect the type: "module" and create the config with export default rather than module.exports = .

Link to repl or repo (highly encouraged)

https://github.com/aldeed/jest-esm-config-issue

envinfo

  System:
    OS: macOS 10.15.3
    CPU: (4) x64 Intel(R) Core(TM) i5-4278U CPU @ 2.60GHz
  Binaries:
    Node: 12.16.0 - ~/.nvm/versions/node/v12.16.0/bin/node
    Yarn: 1.21.1 - /usr/local/bin/yarn
    npm: 6.13.4 - ~/.nvm/versions/node/v12.16.0/bin/npm
  npmPackages:
    jest: ^25.5.2 => 25.5.2 

[aldeed]

Opened at request of @SimenB here: #9430 (comment)

[SimenB]

Thanks! I'll take a look tonight

[SimenB]

Looked now - this is a bug in Node. If you remove the --experimental-vm-modules flag, this is the error: Error: Jest: Your version of Node does not support dynamic import - please enable it or use a .cjs file extension for file /Users/simen/repos/jest-esm-config-issue/jest.config.js

Node 12 requires a flag to activate https://nodejs.org/docs/latest-v12.x/api/esm.html#esm_enabling

Adding that makes the test pass.

I've opened a bug report: nodejs/node#33202

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