`get` properties break record merging

In Collection#add when onConflict === 'merge' the utils.deepMixin is called on records, but when a record has a property with only getter it breaks.

[altschuler]

Great! Very informative, thank you very much! And thank you very, very much for js-data! 😃

[jmdobry]

You ran into this issue because of the way TypeScript compiles ES2015 classes to ES5. According to the ES2015 spec, your getter property should be non-enumerable, but TypeScript produces an enumerable property, hence why it is seen by utils.deepMixIn as it iterates over properties of the record.

You can change it to a method, as you mentioned, or you could add a setter that does nothing, or you can modify it to be non-enumerable.

Option 1:

export class Person extends Record {
  age: number;
  isAdult () { return this.age > 18 }
}

Option 2:

export class Person extends Record {
  age: number;
  get isAdult () { return this.age > 18 }
  set isAdult () {}
}

Option 3:

export class Person extends Record {
  age: number;
  get isAdult () { return this.age > 18 }
}
Object.defineProperty(
  Person.prototype,
  Object.assign(
    Object.getOwnPropertyDescriptor(Person.prototype, 'isAdult'),
    {
      enumerable: false
    }
  ),
  'isAdult'
)

EDIT: Fixed typo in Option 3 code