Bugfix/slot super (#226)

.travis.yml

@@ -18,6 +18,8 @@ matrix:
       env: TOXENV=py36
     - python: "pypy"
       env: TOXENV=pypy
+    - python: "pypy3.5-5.8.0"
+      env: TOXENV=pypy3
 
     # Meta
     - python: "3.6"

CHANGELOG.rst

@@ -24,9 +24,12 @@ Deprecations:
 Changes:
 ^^^^^^^^
 
-- Fix *str* on Python 2 when ``slots=True``.
+- ``super()`` and ``__class__`` now work on Python 3 when ``slots=True``.
+  `#102 <https://github.com/python-attrs/attrs/issues/102>`_
+  `#226 <https://github.com/python-attrs/attrs/issues/226>`_
+- The combination of ``str=True`` and ``slots=True`` now works on Python 2.
   `#198 <https://github.com/python-attrs/attrs/issues/198>`_
-- ``attr.Factory`` is now hashable again.
+- ``attr.Factory`` is hashable again.
   `#204 <https://github.com/python-attrs/attrs/issues/204>`_
 
 

src/attr/_compat.py

@@ -1,10 +1,12 @@
 from __future__ import absolute_import, division, print_function
 
+import platform
 import sys
 import types
 
 
 PY2 = sys.version_info[0] == 2
+PYPY = platform.python_implementation() == "PyPy"
 
 
 if PY2:
@@ -88,3 +90,12 @@ def iterkeys(d):
 
     def metadata_proxy(d):
         return types.MappingProxyType(dict(d))
+
+if PYPY:  # pragma: no cover
+    def set_closure_cell(cell, value):
+        cell.__setstate__((value,))
+else:
+    import ctypes
+    set_closure_cell = ctypes.pythonapi.PyCell_Set
+    set_closure_cell.argtypes = (ctypes.py_object, ctypes.py_object)
+    set_closure_cell.restype = ctypes.c_int

src/attr/_make.py

@@ -6,7 +6,14 @@
 from operator import itemgetter
 
 from . import _config
-from ._compat import PY2, iteritems, isclass, iterkeys, metadata_proxy
+from ._compat import (
+    PY2,
+    iteritems,
+    isclass,
+    iterkeys,
+    metadata_proxy,
+    set_closure_cell,
+)
 from .exceptions import (
     DefaultAlreadySetError,
     FrozenInstanceError,
@@ -373,12 +380,27 @@ def wrap(cls):
                 # It might not actually be in there, e.g. if using 'these'.
                 cls_dict.pop(ca_name, None)
             cls_dict.pop("__dict__", None)
+            old_cls = cls
 
             qualname = getattr(cls, "__qualname__", None)
             cls = type(cls)(cls.__name__, cls.__bases__, cls_dict)
             if qualname is not None:
                 cls.__qualname__ = qualname
 
+            # The following is a fix for
+            # https://github.com/python-attrs/attrs/issues/102.  On Python 3,
+            # if a method mentions `__class__` or uses the no-arg super(), the
+            # compiler will bake a reference to the class in the method itself
+            # as `method.__closure__`.  Since we replace the class with a
+            # clone, we rewrite these references so it keeps working.
+            for item in cls.__dict__.values():
+                closure_cells = getattr(item, "__closure__", None)
+                if not closure_cells:  # Catch None or the empty list.
+                    continue
+                for cell in closure_cells:
+                    if cell.cell_contents is old_cls:
+                        set_closure_cell(cell, cls)
+
         return cls
 
     # attrs_or class type depends on the usage of the decorator.  It's a class

tests/test_slots.py

@@ -13,6 +13,8 @@
 
 import attr
 
+from attr._compat import PY2
+
 
 @attr.s
 class C1(object):
@@ -30,6 +32,14 @@ def classmethod(cls):
     def staticmethod():
         return "staticmethod"
 
+    if not PY2:
+        def my_class(self):
+            return __class__  # NOQA: F821
+
+        def my_super(self):
+            """Just to test out the no-arg super."""
+            return super().__repr__()
+
 
 @attr.s(slots=True, hash=True)
 class C1Slots(object):
@@ -47,6 +57,14 @@ def classmethod(cls):
     def staticmethod():
         return "staticmethod"
 
+    if not PY2:
+        def my_class(self):
+            return __class__  # NOQA: F821
+
+        def my_super(self):
+            """Just to test out the no-arg super."""
+            return super().__repr__()
+
 
 def test_slots_being_used():
     """
@@ -298,3 +316,52 @@ class C2(C1Bare):
     hash(c2)  # Just to assert it doesn't raise.
 
     assert {"x": 1, "y": 2, "z": "test"} == attr.asdict(c2)
+
+
+@pytest.mark.skipif(PY2, reason="closure cell rewriting is PY3-only.")
+def test_closure_cell_rewriting():
+    """
+    Slot classes support proper closure cell rewriting.
+
+    This affects features like `__class__` and the no-arg super().
+    """
+    non_slot_instance = C1(x=1, y="test")
+    slot_instance = C1Slots(x=1, y="test")
+
+    assert non_slot_instance.my_class() is C1
+    assert slot_instance.my_class() is C1Slots
+
+    # Just assert they return something, and not an exception.
+    assert non_slot_instance.my_super()
+    assert slot_instance.my_super()
+
+
+@pytest.mark.skipif(PY2, reason="closure cell rewriting is PY3-only.")
+def test_closure_cell_rewriting_inheritance():
+    """
+    Slot classes support proper closure cell rewriting when inheriting.
+
+    This affects features like `__class__` and the no-arg super().
+    """
+    @attr.s
+    class C2(C1):
+        def my_subclass(self):
+            return __class__  # NOQA: F821
+
+    @attr.s
+    class C2Slots(C1Slots):
+        def my_subclass(self):
+            return __class__  # NOQA: F821
+
+    non_slot_instance = C2(x=1, y="test")
+    slot_instance = C2Slots(x=1, y="test")
+
+    assert non_slot_instance.my_class() is C1
+    assert slot_instance.my_class() is C1Slots
+
+    # Just assert they return something, and not an exception.
+    assert non_slot_instance.my_super()
+    assert slot_instance.my_super()
+
+    assert non_slot_instance.my_subclass() is C2
+    assert slot_instance.my_subclass() is C2Slots

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = py27,py34,py35,py36,pypy,flake8,manifest,docs,readme,coverage-report
+envlist = py27,py34,py35,py36,pypy,pypy3,flake8,manifest,docs,readme,coverage-report
 
 
 [testenv]