isolatedModules after migrating global to transform config

[radahh-rest]

In our project we have around 900 files generated from a few API Swagger docs using OpenAPI generator and type checking these for every test (suite?) caused our tests to run extremely slowly. So we settled on using the isolatedModules feature to speed up tests, as we do need to include all files.

As part of the version update from 28.x to 29.x, we converted the global config as directed however this does not appear to have any affect as the tests are now taking multiple minutes to complete and melting my CPU.

I also reverted to 28.x and tried the transform syntax and the same slowness is seen there also, so rather than being a specific regression in the version, I suspect that the transform code path is not handling isolatedModules.

I did checkout the repo and take a quick look but I'm unfamiliar with the code and so far have found nothing obvious. If you have a few tips on tracing the code in the 28.x release I can see if there is a quick patch to contribute.

I found this unanswered issue on SO, to which I added a comment:
https://stackoverflow.com/questions/73687337/disable-type-checking-stopped-working-after-ts-jest-upgrade-to-29-0

[ahnpnl]

If you are using transform, please remove preset

[prashanthkul]

We are facing the same issue with isolatedModules: true, we see performance improvements when we have it as part of the globals config but when we try to use the transform syntax the performance gains are gone.

We do not have a preset as part of our config, do you see any issues with the below config?

const nxPreset = require('@nx/jest/preset')

module.exports = {
  ...nxPreset,
  transform: {
    '^.+\\.(ts|mjs|js|html|svg)$': [
      'jest-preset-angular',
      {
        tsconfig: '<rootDir>/tsconfig.spec.json',
        stringifyContentPathRegex: '\\.(html|svg)$',
      },
    ],
    "\\.ts$": [
      'ts-jest',
      { isolatedModules: true },
    ],
  },
  transformIgnorePatterns: ['node_modules/(?!.*\\.mjs$)'],
  snapshotSerializers: [
    'jest-preset-angular/build/serializers/no-ng-attributes',
    'jest-preset-angular/build/serializers/ng-snapshot',
    'jest-preset-angular/build/serializers/html-comment',
  ],
  resolver: '@nx/jest/plugins/resolver',
  moduleFileExtensions: ['ts', 'js', 'mjs', 'html', 'json', 'svg'],
  moduleNameMapper: {
    'lodash-es': 'lodash',
  },
  globals: {},
  coverageReporters: ['text', 'lcov'],
  maxWorkers: 1,
  passWithNoTests: true,
  snapshotFormat: { escapeString: true, printBasicPrototype: true }
}