Preserve the prototype when setting in an object

[chrisbouchard]

It would be good if set preserved the prototype, so that it can be used with instances of classes with methods.

[chrisbouchard]

I'm working on a merge request right now. I have to figure out how to tag this issue.

[kube]

Do you have an example use case for this?

I'm not really convinced by keeping prototypes on objects handled my Monolite, but I could change my mind if you show a concrete use-case for this.

[chrisbouchard]

Here is the use case I have in mind:

class Person {
    constructor(public firstName: string, public lastName: string) {}
    fullName(): string { return `${firstName} ${lastName}`; }
}

const person1 = new Person('Adam', 'West');
const person2 = set(person1, _ => _.lastName)('Savage');

person1.fullName();  // 'Adam West'
person2.fullName();  // Should be 'Adam Savage', but currently will cause an error

[chrisbouchard]

Also, it just seems right that x instanceof y if and only if set(x, f)(a) instanceof y, which requires that the prototype be preserved.

[nahuel]

Note, lodash/fp set preserves the proto correctly:

m = require('monolite')
f = require('lodash/fp')

class C { constructor() { this.a = 1}}
var obj = new C()

m.set(obj, _ => _.a)(3) instanceof C  //=> false
f.set(['a'], 3, obj)    instanceof C  //=> true

I think monolite must also preserve the proto, is the more useful, well-typed and unsurprising behavior.

[kube]

Ok, Nominal Typing convinced me.

I will add support for prototype tomorrow. (Your PR cannot be merged as I changed a lot of things in Monolite since, and in particular passed from Mocha to Jest)