Problem rewiring exported class that uses composition

[edwmurph]

To recreate this problem, create the following 3 files, and run node test.js.

Rewiring the "Car" module again after changing the composed "Engine" instance returns a fresh Car instance, but the rewired change to the composed "Engine" via __set__ is persisted in the "fresh" instance.

// Engine.js
class Engine {
  start() {
    return 'engine started';
  }
}

module.exports = new Engine();

// Car.js
const engine = require('./Engine');

class Car {
  constructor( engine ) {
    this.engine = engine;
  }
}

const car = new Car( engine );

module.exports = car;

// test.js
const rewire = require('rewire');

const car1 = rewire('./Car')
console.log( 'car1.engine.start():', car1.engine.start() );

car1.__set__('car.engine.start', () => 'changed');
console.log( 'car1.engine.start():', car1.engine.start() );
 
const car2 = rewire('./Car')
console.log( 'car2.engine.start():', car2.engine.start() );

console.log(car1 === car2);

/* outputs:
car1.engine.start(): engine started
car1.engine.start(): changed
car2.engine.start(): changed
false
*/