Integrate classes/transformer-plugin with ts-jest

[GwendalBroudin-Emoko]

Is your feature request related to a problem? Please describe.

Currently, transformer-plugin can't be used with jest, this create a big difference in behaviour with the runtime environment.

Describe the solution you'd like

The perfect solution would be to have the transformer-plugin as an astTransformers in ts-jest like this

import type { JestConfigWithTsJest } from 'ts-jest';

const jestConfig: JestConfigWithTsJest = {
  moduleFileExtensions: ['js', 'json', 'ts'],
  rootDir: '..',
  moduleDirectories: ['node_modules', '<rootDir>'],
  testRegex: '.*\\.spec\\.ts$',
  transform: {
    '^.+\\.(t|j)s$': [
      'ts-jest',
      {
        astTransformers: {
          before: ['@automapper/classes/transformer-plugin'],
        },
      },
    ],
  },
  collectCoverageFrom: ['**/*.(t|j)s'],
  coverageDirectory: '../coverage',
  testEnvironment: 'node',
};

export default jestConfig;

Describe alternatives you've considered

No response

Additional context

As is, this config produce the following error:

ts-jest[config] (WARN) The AST transformer {{file}} must have an `export const version = <your_transformer_version>` {
  file: '.../node_modules/@automapper/classes/transformer-plugin/index.cjs'
}

...

 FAIL  src/modules/jobs/crud/job.mapping.spec.ts
  ● Test suite failed to run

    TypeError: beforeTransformer.factory is not a function

      at node_modules/.pnpm/[email protected]_r24ewcothphvclnu77pxb4u4se/node_modules/ts-jest/dist/legacy/compiler/ts-compiler.js:222:42
          at Array.map (<anonymous>)
      at TsCompiler._makeTransformers (node_modules/.pnpm/[email protected]_r24ewcothphvclnu77pxb4u4se/node_modules/ts-jest/dist/legacy/compiler/ts-compiler.js:221:47)
      at Object.getCustomTransformers (node_modules/.pnpm/[email protected]_r24ewcothphvclnu77pxb4u4se/node_modules/ts-jest/dist/legacy/compiler/ts-compiler.js:294:63)
      at Object.getEmitOutput (node_modules/.pnpm/[email protected]/node_modules/typescript/lib/typescript.js:168067:73)
      at TsCompiler.getCompiledOutput (node_modules/.pnpm/[email protected]_r24ewcothphvclnu77pxb4u4se/node_modules/ts-jest/dist/legacy/compiler/ts-compiler.js:142:48)
      at TsJestCompiler.getCompiledOutput (node_modules/.pnpm/[email protected]_r24ewcothphvclnu77pxb4u4se/node_modules/ts-jest/dist/legacy/compiler/ts-jest-compiler.js:14:39)
      at TsJestTransformer.processWithTs (node_modules/.pnpm/[email protected]_r24ewcothphvclnu77pxb4u4se/node_modules/ts-jest/dist/legacy/ts-jest-transformer.js:265:37)
      at TsJestTransformer.process (node_modules/.pnpm/[email protected]_r24ewcothphvclnu77pxb4u4se/node_modules/ts-jest/dist/legacy/ts-jest-transformer.js:188:24)
      at ScriptTransformer.transformSource (node_modules/.pnpm/@[email protected]/node_modules/@jest/transform/build/ScriptTransformer.js:519:31)
      at ScriptTransformer._transformAndBuildScript (node_modules/.pnpm/@[email protected]/node_modules/@jest/transform/build/ScriptTransformer.js:648:40)
      at ScriptTransformer.transform (node_modules/.pnpm/@[email protected]/node_modules/@jest/transform/build/ScriptTransformer.js:700:19)