attr.s(frozen=True) breaks writeable properties

[exarkun]

(txkube) exarkun@baryon:~/Work/LeastAuthority/txkube$ cat brokenattrs.py
import attr

@attr.s(frozen=True)
class X(object):
    y = attr.ib()

    @property
    def z(self):
        return 3

    @z.setter
    def z(self, value):
        print("z=", value)

X(y=None).z = 10
(txkube) exarkun@baryon:~/Work/LeastAuthority/txkube$ python brokenattrs.py 
Traceback (most recent call last):
  File "brokenattrs.py", line 15, in <module>
    X(y=None).z = 10
  File "/home/exarkun/Environments/txkube/local/lib/python2.7/site-packages/attr/_make.py", line 201, in _frozen_setattrs
    raise FrozenInstanceError()
attr.exceptions.FrozenInstanceError
(txkube) exarkun@baryon:~/Work/LeastAuthority/txkube$ 

[hynek]

Heh we freeze the classes for good ATM. There seems to be interest in a more…flexible freezing process (c.f. also #133).

[joeblackwaslike]

I opened an issue for with initial pull request for customizing setattr and delattr for frozen classes here: #378

[maz808]

I'm having trouble understanding the solution to this. Is this still not supported or am I missing something? What I ultimately want to do is be able to set a single attribute of a class that has inherited a frozen status. Is this even possible?

[hynek]

you can always set any attribute using object.__setattr__. An example is in https://www.attrs.org/en/stable/init.html#post-init

[maz808]

you can always set any attribute using object.__setattr__. An example is in https://www.attrs.org/en/stable/init.html#post-init

I have started doing that in a method for the frozen class, but I really would prefer this:
class_instance.attribute = value
over this: class_instance.change_attribute(value)

I guess I should have mentioned that. I appreciate the response, but I'm still uncertain if what I want is even doable right now.

[hynek]

At this point, allowing for this would break a lot of contracts since attrs makes assumptions based on the frozen-ness of a class (most notably, hashability) so I don't want to add features that surprisingly would undermine that. We've added many features for pluggable control of setters, tho!