[Bug]: make jsdom accessible to extending environments again

Version

27.4.7

Steps to reproduce

I prepared a small reproduction repository. It uses a custom TS environment that tries to access this.dom and fails.

To see for yourself:

• clone the repo
• run npm install
• run npx jest

Expected behavior

Jest Environments that extend jest-environment-jsdom should be able to access this.dom.

Basically, this should work:

export class JSDOMEnvironmentGlobal extends JSDOMEnvironment {
  constructor(config, options) {
    super(config, options);

   // this line triggers the error
    this.global.jsdom = this.dom;
  }
}

Actual behavior

That doesn’t work if the project uses TypeScript because this.dom has recently been made private.

The error you get if you try to access this.dom in an environment:

 Property 'dom' is private and only accessible within class 'JSDOMEnvironment'.

Additional context

jest-environment-jsdom-global (a popular npm package that uses the same technique to make jsdom available) is currently unaffected because it uses JS and the transpiled CommonJS version of jest-environment-jsdom doesn’t enforce this.dom to be private. If jest changes its bundling process in the future, this could also fail for projects using JS.

I think it’d be great if jsdom continued to be accessible for custom environments since that enables use cases that would otherwise not be possible.

Environment

System:
    OS: macOS 12.1
    CPU: (8) x64 Apple M1
  Binaries:
    Node: 14.16.1 - /usr/local/bin/node
    Yarn: 2.4.3 - ~/.npm-global/bin/yarn
    npm: 7.11.2 - /usr/local/bin/npm

[robin-drexler]

@SimenB PR: https://github.com/facebook/jest/pull/12232

curious what’s changed that makes this possible now? 😃

[github-actions[bot]]

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