copy.deepcopy() broken on Entity instances

[bworrell]

Calling copy.deepcopy() on an Entity instance doesn't work if it has any TypedField values set.

The deepcopy() call works, but the TypedField value resolution is broken on set fields:

>>> a = Address()
>>> a.address_value = "foobar"
>>> print a.address_value
foobar
>>> # make a deep copy
>>>copied = copy.deepcopy(a)
>>>print copied.address_value
None

This is because we made the Entity._fields dictionary keyed off of TypedField instances. The copy.deepcopy() call creates new keys and breaks the connection between the TypedField descriptor and the _fields entry.

[bworrell]

Fixed in https://github.com/CybOXProject/mixbox/commit/cfd8909a8e8985d7d597e408791b3289f28ac675.

I resolved this by essentially making __copy__() and __deepcopy__() just return self rather than creating a new instance. I think this is fine because TypedField is designed to expect that there will only ever be one instance of itself for a given class.

An alternative would be to control __deepcopy__ at the Entity level, but that got pretty complicated quickly, so I opted for this solution. We can reopen later if this causes problems.

[gtback]

Why define __deepcopy__ to do something other than actually make a copy? If it's causing unexpected behavior (and I would agree losing field values is unexpected :stuck_out_tongue: ), why not just raise an Exception in __deepcopy__. If people are calling copy.deepcopy, I imagine they expect to be able to mutate one or the other without affecting the other, which is certainly unexpected.

[gtback]

Nevermind. I didn't realize you defined it on TypedField, not Entity. Nothing to see here, move along :smile:

[bworrell]

:D