This is my patch:
[ 635933 ] make some type attrs writable
Plus a couple of extra tests beyond what's up there.
It hasn't been as carefully reviewed as it perhaps should, so all readers
are encouraged, nay exhorted, to give this a close reading.
There are still a couple of oddities related to assigning to __name__,
but I intend to solicit python-dev's opinions on these.
diff --git a/Lib/test/test_descr.py b/Lib/test/test_descr.py
index 2c2a42b..b230d39 100644
--- a/Lib/test/test_descr.py
+++ b/Lib/test/test_descr.py
@@ -3434,6 +3434,93 @@
# (before PyType_Ready(tuple) is called)
type.mro(tuple)
+def mutable_bases():
+ # stuff that should work:
+ class C(object):
+ pass
+ class C2(object):
+ def __getattribute__(self, attr):
+ if attr == 'a':
+ return 2
+ else:
+ return super(C2, self).__getattribute__(attr)
+ def meth(self):
+ return 1
+ class D(C):
+ pass
+ class E(D):
+ pass
+ d = D()
+ e = E()
+ D.__bases__ = (C2,)
+ vereq(d.meth(), 1)
+ vereq(e.meth(), 1)
+ vereq(d.a, 2)
+ vereq(e.a, 2)
+ vereq(C2.__subclasses__(), [D])
+
+ # stuff that shouldn't:
+ class L(list):
+ pass
+
+ try:
+ L.__bases__ = (dict,)
+ except TypeError:
+ pass
+ else:
+ raise TestFailed, "shouldn't turn list subclass into dict subclass"
+
+ try:
+ list.__bases__ = (dict,)
+ except TypeError:
+ pass
+ else:
+ raise TestFailed, "shouldn't be able to assign to list.__bases__"
+
+ try:
+ del D.__bases__
+ except TypeError:
+ pass
+ else:
+ raise TestFailed, "shouldn't be able to delete .__bases__"
+
+ try:
+ D.__bases__ = (D,)
+ except TypeError:
+ pass
+ else:
+ # actually, we'll have crashed by here...
+ raise TestFailed, "shouldn't be able to create inheritance cycles"
+
+ # let's throw a classic class into the mix:
+ class Classic:
+ def meth2(self):
+ return 3
+
+ D.__bases__ = (C, Classic)
+
+ vereq(d.meth2(), 3)
+ vereq(e.meth2(), 3)
+ try:
+ d.a
+ except AttributeError:
+ pass
+ else:
+ raise TestFailed, "attribute should have vanished"
+
+ try:
+ D.__bases__ = (Classic,)
+ except TypeError:
+ pass
+ else:
+ raise TestFailed, "new-style class must have a new-style base"
+
+def mutable_names():
+ class C(object):
+ pass
+
+ C.__name__ = 'C'
+
def test_main():
do_this_first()
class_docstrings()
@@ -3513,6 +3600,8 @@
slotmultipleinheritance()
testrmul()
testipow()
+ mutable_bases()
+ mutable_names()
if verbose: print "All OK"
if __name__ == "__main__":