5.1.2 (2020-10-01)
==================
- Make sure to call each invariant only once when validating invariants.
Previously, invariants could be called multiple times because when an
invariant is defined in an interface, it's found by in all interfaces
inheriting from that interface. See `pull request 215
<https://github.com/zopefoundation/zope.interface/pull/215/>`_.
5.1.1 (2020-09-30)
==================
- Fix the method definitions of ``IAdapterRegistry.subscribe``,
``subscriptions`` and ``subscribers``. Previously, they all were
defined to accept a ``name`` keyword argument, but subscribers have
no names and the implementation of that interface did not accept
that argument. See `issue 208
<https://github.com/zopefoundation/zope.interface/issues/208>`_.
- Fix a potential reference leak in the C optimizations. Previously,
applications that dynamically created unique ``Specification``
objects (e.g., used ``@implementer`` on dynamic classes) could
notice a growth of small objects over time leading to increased
garbage collection times. See `issue 216
<https://github.com/zopefoundation/zope.interface/issues/216>`_.
.. caution::
This leak could prevent interfaces used as the bases of
other interfaces from being garbage collected. Those interfaces
will now be collected.
One way in which this would manifest was that ``weakref.ref``
objects (and things built upon them, like
``Weak[Key|Value]Dictionary``) would continue to have access to
the original object even if there were no other visible
references to Python and the original object *should* have been
collected. This could be especially problematic for the
``WeakKeyDictionary`` when combined with dynamic or local
(created in the scope of a function) interfaces, since interfaces
are hashed based just on their name and module name. See the
linked issue for an example of a resulting ``KeyError``.
Note that such potential errors are not new, they are just once
again a possibility.
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