Component's `data` property must be function restriction

What problem does this feature solve?

Take off this restriction would increase the consistency.

I understand that every component needs a copy of the data object. But can’t you just copy the data object under the hood? Are there any benefits by using a function instead?

What does the proposed API look like?

Vue.component('foo', {
    data: {
        foo: 'bar'
    }
});

[fnlctrl]

But can’t you just copy the data object under the hood? Are there any benefits by using a function instead?

Deep cloning objects (copy the data object under the hood) causes 1). heavy performance overhead 2). bloated code for a deep clone implementation. So it’s better to just use a function to create a fresh object every time.

[jacekkarczmarczyk]

Object.assign is not deep