Jest transform support / documentation

Hi, thanks for the awesome library. Nice to see proper TypeScript support in React Native.

As Jest is the default test runner in React Native projects created by by the react-native cli tool, it would be nice to see support or documentation on how to use this library as the transformer for Jest as well.

Of course the alternative is to use https://github.com/lozinsky/typescript-babel-jest, but would somehow be nice to use the same transformation for tests and production.

[vovkasm]

I just try preprocess jest tests with this module and it seems to work well with small glue code. Although my test suite is small and I may not detect all edge cases, it would be good to have this “glue” in package itself and improve it together.

My config: jest/preprocessor.js (actually it is adaptation of RN jest preprocessor)

var tsTransformer = require('react-native-typescript-transformer')
var rnTransformer = require('react-native/jest/preprocessor')

var preprocessor = Object.assign({}, rnTransformer, {
  process (src, file) {
    return tsTransformer.transform({
      filename: file,
      localPath: file,
      options: {
        dev: true,
        inlineRequires: true,
        platform: '',
        projectRoot: '',
        retainLines: true,
      },
      src,
    }).code
  },
})

module.exports = preprocessor

package.json (jest config part)

  "jest": {
    "preset": "react-native",
    "transform": {
      "^.+\\.[jt]sx?$": "<rootDir>/jest/preprocessor.js"
    },
    "testMatch": [
      "**/*.spec.{js,jsx,ts,tsx}"
    ],
    "moduleFileExtensions": [
      "ts",
      "tsx",
      "js"
    ]
  },

What do you think?

[ds300]

Happy to have your input @GeeWee !

I agree that it makes most sense to focus on ts-jest. It should work, and it has a lot of useful things that react-native-typescript-transformer lacks.