Custom transformer on top of ts-jest

[acalvo]

Hi!

I'm struggling to make a simple transformation to the source code (TS file) before ts-jest makes its transformations.

As Jest doesn't accept adding two transformers for the same type file (.ts), I was trying to add a custom transformer that inside of it makes use of ts-jest. Something like this:

jest.config.js

module.exports = {
    ...
    "transform": {
        "\\.ts$":
            "<rootDir>/src/jest-file-transformer.js",
    },
};

jest-file-transformer.js

module.exports = {
  process: function (src, filename, config, options) {
    return require('ts-jest').process(myCustomTransform(src), filename, config, options);
  },
};

But this code won't work... Can someone point me in the right direction?

Thank you!!

[ahnpnl]

To work with Jest 27, your jest-file-transformer.js must have this structure

const tsJestTransformer = require('ts-jest').createTransformer();

module.exports = { 
    createTransformer: () => {
        return {
             process: function (src, filename, config, options) {
                   return tsJestTransformer.process(myCustomTransform(src), filename, config, options)
             }
        }
   }
}