Istanbul coverage fix for Nest.JS code

jest.fixCoverage.js

// HOW TO USE:
// 1. copy the code below into a new file (e.g. `jest.fixCoverage.js`).
// 2. In your `jest.config.js`, have this for the `transform` config:
//    transform: { '^.+\\.[tj]sx?$': '<rootDir>/jest.fixCoverage.js' },

const { default: tsJest } = require('ts-jest')

module.exports = fixIstanbulDecoratorCoverageTransformer()

function fixIstanbulDecoratorCoverageTransformer() {
  const transformer = tsJest.createTransformer()
  const process = transformer.process.bind(transformer)

  transformer.process = (...args) => {
    let result = process(...args)
    result = result.replaceAll('__decorate', '/* istanbul ignore next */__decorate')
    result = result.replace(/(\(.*__metadata\)\("design:paramtypes",.*)/g, '/* istanbul ignore next */$1')
    result = result.replace(/(\(.*__metadata\)\("design:returntype",.*)/g, '/* istanbul ignore next */$1')
    result = result.replace(/(\(.*__metadata\)\("design:type",.*)/g, '/* istanbul ignore next */$1')
    result = result.replace(/(\(.*__metadata\)\("design:type", )(.*)/g, '$1/* istanbul ignore next */$2')
    return result
  }

  return transformer
}