Extension errors when re-defining a property.

[justinbmeyer]

http://jsbin.com/meyuhateqe/edit?html,js,output

cc @bmomberger-bitovi

[justinbmeyer]

Taking this example:

var A = DefineMap.extend("A", {
    foo: {
        type: "string",
        value: "blah"
    }
});


A.extend("B", {
    foo: {
        type: "string",
        value: "flub"
    }
});

The problem here is that when B is being created, an instance of A is created (we'll call this aA. aA is the prototype of B. We set the new foo on aA in _overwrite like:

aA.foo = { type: "string",  value: "flub" }

This causes the foo setter to run, which accesses aA._data, which sets up the non-configurable aA._data.

I'm not sure what the right solution is.

One solution might be to decorate aA as it's being extended (similar to what we do with __inSetup here ).

The better solution is to change _overwrite to use Object.defineProperty() to avoid the setter.