Fix shared array reference

[takahirox]

Description:

This PR fixes the issue "Array property type default share the same reference" #2554

Changes proposed:

• clone default value with .slice() if it's an array in parseProperty() of schema.js

[takahirox]

Ah, wait.
Maybe I think I should've done that in arrayParse() of propertyTypes.js.
I'll update...

[ngokevin]

Do we need to do something similar for objects as well?

[dmarcos]

What do you mean by objects? The only types we have that can receive an object are vec2, vec3 and vec4 and those are already copied when parsed: https://github.com/aframevr/aframe/blob/master/src/utils/coordinates.js#L17

[ngokevin]

In case I define my own property type and set the default value as an object. I often create "schemaless" components that just accept flexible data.

default: {},
parse: function (val) {
  // ... Parse to object or pass through object.
}

[dmarcos]

if you do that is the parse function that should make sure that the object is copied.

[dmarcos]

Copying objects is inefficient and should be a deliberate decision. I think sharing objects is a more sensible default

[dmarcos]

Sure but your custom parse function can copy the objects

[ngokevin]

That's more of a weird workaround. It's not really parsing, I'd have to run a check if it's exactly the default object to figure to copy it, and I only need it to be done once if it's using the default value and not on every parse. I propose to handle it because the case is unexpected.

The object copy won't be hit that often if we handle the logic here. Only once per property initialization, and only if it's usually the default value. Plus, it's usually an empty object.

[dmarcos]

Can we have an object type in the property types that is shallow? It allows just one level where the attributes are primitive types based on the default value? Should we deal with this in a separate issue / PR?

[ngokevin]

I don't really have a need for that. I might have a component that generates entities. Or I sometimes use it to create schemaless components. One level is often limiting. I just the component to hold whatever data I have and pass it on.

AFRAME.registerComponent('creator', {
  schema: {
    geometry: myCustomObjPropertyType,
    material: myCustomObjPropertyType
  }
});

[ngokevin]

Will merge though and figure it out later.