Custom transform options return jest options

[tiagoporto]

🐛 Bug Report

To Reproduce

Steps to reproduce the behavior:

jest.config.js

module.exports = {
  roots: ['<rootDir>/src'],
  moduleFileExtensions: ['ts', 'tsx', 'js', 'jsx'],
  transform: {
    '\\.[jt]sx?$': 'babel-jest',
+    '\\.json$': ['<rootDir>/custom-transformer.js', { prefix: 'app' }],
  },
}

custom-transformer.js

module.exports = {
  process(sourceText, sourcePath, transformOptions) {
    console.log(transformOptions)

    return sourceText
  },
}

The parameter transformOptions returns the entire jest config

{
  automock: false,
  cache: false,
  cacheDirectory: '/private/var/folders/g0/c7ddp8415wv43nw2r2jbys7h0000gn/T/jest_dx',
  clearMocks: false,
  coveragePathIgnorePatterns: [ '/node_modules/' ],
  cwd: '/Volumes/Data/Development/gerador-validador-cpf',
  detectLeaks: false,
  detectOpenHandles: false,
  errorOnDeprecated: false,
  extraGlobals: [],
  forceCoverageMatch: [],
  globals: {},
  haste: { computeSha1: false, throwOnModuleCollision: false },
  injectGlobals: true,
  moduleDirectories: [ 'node_modules' ],
  moduleFileExtensions: [ 'ts', 'tsx', 'js', 'jsx' ],
  moduleNameMapper: []
  modulePathIgnorePatterns: [],
  name: 'cb79043c053af8ccc4b659f65a7e5758',
  prettierPath: 'prettier',
  resetMocks: false,
  resetModules: false,
  restoreMocks: false,
  rootDir: '/Volumes/Data/Development/gerador-validador-cpf',
  roots: [ '/Volumes/Data/Development/gerador-validador-cpf/src' ],
  runner: 'jest-runner',
  setupFiles: [],
  setupFilesAfterEnv: [],
  skipFilter: false,
  slowTestThreshold: 5,
  snapshotSerializers: [],
  testEnvironment: '/Volumes/Data/Development/gerador-validador-cpf/node_modules/jest-environment-jsdom/build/index.js',
  testEnvironmentOptions: {},
  testLocationInResults: false,
  testMatch: [ '**/__tests__/**/*.[jt]s?(x)', '**/?(*.)+(spec|test).[tj]s?(x)' ],
  testPathIgnorePatterns: [ '/node_modules/' ],
  testRegex: [],
  testRunner: '/Volumes/Data/Development/gerador-validador-cpf/node_modules/jest-jasmine2/build/index.js',
  testURL: 'http://localhost',
  timers: 'real',
  transform: [
    [
      '\\.[jt]sx?$',
      '/Volumes/Data/Development/gerador-validador-cpf/node_modules/babel-jest/build/index.js',
      {}
    ],
    [
      '\\.json$',
      '/Volumes/Data/Development/gerador-validador-cpf/custom-transformer.js',
      [Object]
    ]
  ],
  transformIgnorePatterns: [ '/node_modules/', '\\.pnp\\.[^\\/]+$' ],
  watchPathIgnorePatterns: []
}

Expected behavior

Is expected only the options for the custom transform

{ prefix: 'app' }

envinfo

 System:
    OS: macOS High Sierra 10.13.6
    CPU: (4) x64 Intel(R) Core(TM) i5-2435M CPU @ 2.40GHz
  Binaries:
    Node: 14.15.3 - /usr/local/bin/node
    npm: 6.14.9 - /usr/local/bin/npm
  npmPackages:
    jest: ^26.6.3 => 26.6.3 

[SimenB]

That's expected in Jest 26 (https://github.com/facebook/jest/blob/v26.6.3/packages/jest-transform/src/ScriptTransformer.ts#L308-L312). However, in Jest 27 (jest@next) the API is changed via #10926

https://github.com/facebook/jest/blob/e3d5491642c336ba76bbc08708345f45ed8d13c6/packages/jest-transform/src/ScriptTransformer.ts#L304-L310

As mentioned in the linked PR you can export a createTransformer function that will receive the options in Jest 26

[tiagoporto]

Thank you @SimenB

[github-actions]

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