Model.toObject() should preserve prototypes (e.g. Date and ObjectID values)

[bajtos]

Suggestion

ATM, toObject() method is implemented via toJSON and thus converts object values to JSON representation. This is problematic e.g. for Date and ObjectID values.

I am proposing to modify toObject() to preserve type of Date, ObjectID and other non-model values. Of course, if a model instance has a property set to a value of another Model, that property must be recursively converted via toObject to a plain object.

Use Cases

Consider the following test demonstrating the problem:

@model()
class Order extends Entity {
  @property({
      type: 'string',
      id: true,
      generated: true,
    })
    id: string;

    @property()
    createdAt: Date;
}

const orderRepo = // ...;
const DATE = new Date(...);
const created = orderRepo.create({
  createdAt: DATE;
});

expect(created.toObject()).to.deepEqual({
  id: created.id,
  createdAt: DATE,
});

The assertion above fails now.

Examples

The test example above should pass.

Acceptance criteria

• .toObject() is updated to handle Date,ObjectID, and other non-model values, and handle recursion into fields that are also Model objects. See : https://github.com/strongloop/loopback-datasource-juggler/blob/master/lib/model.js#L422
• Update or add mocha test cases in https://github.com/strongloop/loopback-datasource-juggler/tree/master/test
• Update documentation

[hacksparrow]

Agreed!

[emonddr]

@bajtos I added the Acceptance Criteria. Please adjust it to your liking; if necessary. thx

Also what is an example of non-model value?

[bajtos]

I added the Acceptance Criteria.

Great, thank you @emonddr!

Also what is an example of non-model value

A plain data object. For example:

@model()
class Foo extends Entity {
  @property({id: true})
    id: number;

    @property()
    data: object;
}

const foo = new Foo({id: 1, data: {key: 'value'}});
expect(foo.toObject().data).to.deepEqual({key: 'value'});

I think the conversion logic should work as follows:

• If the value is not an object, then keep it as-is
• If the value is an array, then (recursively) convert all items of that array
• If the value has .toObject method, then call it to perform the conversion
• Otherwise keep the value as-is

I have also checked the implementation of toObject in LB 3.x (see loopback-datasource-juggler:lib/model.js), I think we should also prepend the following rules:

• If the value is a function, then exclude it from the result
• If the property is configured as hidden, then exclude its value from the result

Here is the full algorithm:

1. If the property is configured as hidden, then exclude its value from the result.
2. If the value is a function, then exclude it from the result.
3. If the value is not an object, then keep it as-is.
4. If the value is an array, then (recursively) convert all items of that array.
5. If the value has .toObject method, then call it to perform the conversion.
6. Otherwise keep the value as-is.