Fix for the jest.config.ts compiler to not interfere with tsconfig.json files

[Gamote]

Summary

This PR resolves #10652.

The bug occurs when the consumer have a tsconfig.json file in the project defining the module configuration. In this case the internal compiler which takes care of processing the jest.config.ts automatically detect that. With this PR, I've added explicit definition on what module we want to use for output.

CHANGELOG.md file was updated to reflect these changes.

[SimenB]

can we add a test as well? just adding a tsconfig file to the e2e test and seeing it still pass, perhaps?

[SimenB]

thanks!

I just noticed const DIR = path.resolve(__dirname, '../jest.config.ts'); - can you rename this to look like a directory instead of looking like a file? just

- const DIR = path.resolve(__dirname, '../jest.config.ts');
+ const DIR = path.resolve(__dirname, '../jest-config-ts');

or something.

Possibly stick it in tmp as well?

[SimenB]

I meant

import {tmpdir} from 'os';`

😅

[Gamote]

@SimenB If I move it to tmp the traverses directory tree up until it finds jest.config test will fail because it can't find the slash package.

[SimenB]

we should install slash in it, then. We have a runYarn helper already - I don't think it takes args, but that should be a simple refactor.

We can do it later, though 🙂

[Gamote]

Ah nice, runYarn is exactly what I was looking for

[Gamote]

@SimenB I've reverted the change with the tmp bacause I couldn't make runYarn to install the slash package. I even tried run('yarn install', DIR) with same module does not exist error.

As you said, we can do it later so we don't need to delay this fix.

Full example:

test('traverses directory tree up until it finds jest.config', () => {
  writeFiles(DIR, {
    '__tests__/a-giraffe.js': `
    const slash = require('slash');
    test('giraffe', () => expect(1).toBe(1));
    test('abc', () => console.log(slash(process.cwd())));
    `,
    'jest.config.ts': `export default {testEnvironment: 'jest-environment-node', testRegex: '.*-giraffe.js'};`,
    'package.json': '{ "devDependencies": { "slash": "^3.0.0" } }',
    'some/nested/directory/file.js': '// nothing special',
  });

  // 1st try with small local refactoring to allow args
  runYarn(DIR, undefined, ['install']);

  // 2nd try
  run('yarn install', DIR);

  const {stderr, exitCode, stdout} = runJest(
    path.join(DIR, 'some', 'nested', 'directory'),
    ['-w=1', '--ci=false'],
    {skipPkgJsonCheck: true},
  );

  // expects...
});

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