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Issue 1294232: Fix errors in metaclass calculation affecting some cases of metaclass inheritance. Patch by Daniel Urban.

This commit is contained in:
Nick Coghlan 2011-10-23 22:04:16 +10:00
parent 711f87ca7d
commit de31b191e5
5 changed files with 242 additions and 22 deletions
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1
Include/object.h
View File

@ -449,6 +449,7 @@ PyAPI_FUNC(PyObject *) PyType_GenericNew(PyTypeObject *,
#ifndef Py_LIMITED_API
PyAPI_FUNC(PyObject *) _PyType_Lookup(PyTypeObject *, PyObject *);
PyAPI_FUNC(PyObject *) _PyObject_LookupSpecial(PyObject *, char *, PyObject **);
PyAPI_FUNC(PyTypeObject *) _PyType_CalculateMetaclass(PyTypeObject *, PyObject *);
#endif
PyAPI_FUNC(unsigned int) PyType_ClearCache(void);
PyAPI_FUNC(void) PyType_Modified(PyTypeObject *);

168
Lib/test/test_descr.py
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@ -625,6 +625,174 @@ class ClassPropertiesAndMethods(unittest.TestCase):
# The most derived metaclass of D is A rather than type.
class D(B, C):
pass
self.assertIs(A, type(D))
# issue1294232: correct metaclass calculation
new_calls = [] # to check the order of __new__ calls
class AMeta(type):
@staticmethod
def __new__(mcls, name, bases, ns):
new_calls.append('AMeta')
return super().__new__(mcls, name, bases, ns)
@classmethod
def __prepare__(mcls, name, bases):
return {}
class BMeta(AMeta):
@staticmethod
def __new__(mcls, name, bases, ns):
new_calls.append('BMeta')
return super().__new__(mcls, name, bases, ns)
@classmethod
def __prepare__(mcls, name, bases):
ns = super().__prepare__(name, bases)
ns['BMeta_was_here'] = True
return ns
class A(metaclass=AMeta):
pass
self.assertEqual(['AMeta'], new_calls)
new_calls[:] = []
class B(metaclass=BMeta):
pass
# BMeta.__new__ calls AMeta.__new__ with super:
self.assertEqual(['BMeta', 'AMeta'], new_calls)
new_calls[:] = []
class C(A, B):
pass
# The most derived metaclass is BMeta:
self.assertEqual(['BMeta', 'AMeta'], new_calls)
new_calls[:] = []
# BMeta.__prepare__ should've been called:
self.assertIn('BMeta_was_here', C.__dict__)
# The order of the bases shouldn't matter:
class C2(B, A):
pass
self.assertEqual(['BMeta', 'AMeta'], new_calls)
new_calls[:] = []
self.assertIn('BMeta_was_here', C2.__dict__)
# Check correct metaclass calculation when a metaclass is declared:
class D(C, metaclass=type):
pass
self.assertEqual(['BMeta', 'AMeta'], new_calls)
new_calls[:] = []
self.assertIn('BMeta_was_here', D.__dict__)
class E(C, metaclass=AMeta):
pass
self.assertEqual(['BMeta', 'AMeta'], new_calls)
new_calls[:] = []
self.assertIn('BMeta_was_here', E.__dict__)
# Special case: the given metaclass isn't a class,
# so there is no metaclass calculation.
marker = object()
def func(*args, **kwargs):
return marker
class X(metaclass=func):
pass
class Y(object, metaclass=func):
pass
class Z(D, metaclass=func):
pass
self.assertIs(marker, X)
self.assertIs(marker, Y)
self.assertIs(marker, Z)
# The given metaclass is a class,
# but not a descendant of type.
prepare_calls = [] # to track __prepare__ calls
class ANotMeta:
def __new__(mcls, *args, **kwargs):
new_calls.append('ANotMeta')
return super().__new__(mcls)
@classmethod
def __prepare__(mcls, name, bases):
prepare_calls.append('ANotMeta')
return {}
class BNotMeta(ANotMeta):
def __new__(mcls, *args, **kwargs):
new_calls.append('BNotMeta')
return super().__new__(mcls)
@classmethod
def __prepare__(mcls, name, bases):
prepare_calls.append('BNotMeta')
return super().__prepare__(name, bases)
class A(metaclass=ANotMeta):
pass
self.assertIs(ANotMeta, type(A))
self.assertEqual(['ANotMeta'], prepare_calls)
prepare_calls[:] = []
self.assertEqual(['ANotMeta'], new_calls)
new_calls[:] = []
class B(metaclass=BNotMeta):
pass
self.assertIs(BNotMeta, type(B))
self.assertEqual(['BNotMeta', 'ANotMeta'], prepare_calls)
prepare_calls[:] = []
self.assertEqual(['BNotMeta', 'ANotMeta'], new_calls)
new_calls[:] = []
class C(A, B):
pass
self.assertIs(BNotMeta, type(C))
self.assertEqual(['BNotMeta', 'ANotMeta'], new_calls)
new_calls[:] = []
self.assertEqual(['BNotMeta', 'ANotMeta'], prepare_calls)
prepare_calls[:] = []
class C2(B, A):
pass
self.assertIs(BNotMeta, type(C2))
self.assertEqual(['BNotMeta', 'ANotMeta'], new_calls)
new_calls[:] = []
self.assertEqual(['BNotMeta', 'ANotMeta'], prepare_calls)
prepare_calls[:] = []
# This is a TypeError, because of a metaclass conflict:
# BNotMeta is neither a subclass, nor a superclass of type
with self.assertRaises(TypeError):
class D(C, metaclass=type):
pass
class E(C, metaclass=ANotMeta):
pass
self.assertIs(BNotMeta, type(E))
self.assertEqual(['BNotMeta', 'ANotMeta'], new_calls)
new_calls[:] = []
self.assertEqual(['BNotMeta', 'ANotMeta'], prepare_calls)
prepare_calls[:] = []
class F(object(), C):
pass
self.assertIs(BNotMeta, type(F))
self.assertEqual(['BNotMeta', 'ANotMeta'], new_calls)
new_calls[:] = []
self.assertEqual(['BNotMeta', 'ANotMeta'], prepare_calls)
prepare_calls[:] = []
class F2(C, object()):
pass
self.assertIs(BNotMeta, type(F2))
self.assertEqual(['BNotMeta', 'ANotMeta'], new_calls)
new_calls[:] = []
self.assertEqual(['BNotMeta', 'ANotMeta'], prepare_calls)
prepare_calls[:] = []
# TypeError: BNotMeta is neither a
# subclass, nor a superclass of int
with self.assertRaises(TypeError):
class X(C, int()):
pass
with self.assertRaises(TypeError):
class X(int(), C):
pass
def test_module_subclasses(self):
# Testing Python subclass of module...

4
Misc/NEWS
View File

@ -10,6 +10,10 @@ What's New in Python 3.2.3?
Core and Builtins
-----------------
- Issue #1294232: In a few cases involving metaclass inheritance, the
interpreter would sometimes invoke the wrong metaclass when building a new
class object. These cases now behave correctly. Patch by Daniel Urban.
- Issue #12604: VTRACE macro expanded to no-op in _sre.c to avoid compiler
warnings. Patch by Josh Triplett and Petri Lehtinen.

61
Objects/typeobject.c
View File

@ -1912,6 +1912,42 @@ PyType_GetFlags(PyTypeObject *type)
return type->tp_flags;
}
/* Determine the most derived metatype. */
PyTypeObject *
_PyType_CalculateMetaclass(PyTypeObject *metatype, PyObject *bases)
{
Py_ssize_t i, nbases;
PyTypeObject *winner;
PyObject *tmp;
PyTypeObject *tmptype;
/* Determine the proper metatype to deal with this,
and check for metatype conflicts while we're at it.
Note that if some other metatype wins to contract,
it's possible that its instances are not types. */
nbases = PyTuple_GET_SIZE(bases);
winner = metatype;
for (i = 0; i < nbases; i++) {
tmp = PyTuple_GET_ITEM(bases, i);
tmptype = Py_TYPE(tmp);
if (PyType_IsSubtype(winner, tmptype))
continue;
if (PyType_IsSubtype(tmptype, winner)) {
winner = tmptype;
continue;
}
/* else: */
PyErr_SetString(PyExc_TypeError,
"metaclass conflict: "
"the metaclass of a derived class "
"must be a (non-strict) subclass "
"of the metaclasses of all its bases");
return NULL;
}
return winner;
}
static PyObject *
type_new(PyTypeObject *metatype, PyObject *args, PyObject *kwds)
{
@ -1955,28 +1991,12 @@ type_new(PyTypeObject *metatype, PyObject *args, PyObject *kwds)
&PyDict_Type, &dict))
return NULL;
/* Determine the proper metatype to deal with this,
and check for metatype conflicts while we're at it.
Note that if some other metatype wins to contract,
it's possible that its instances are not types. */
nbases = PyTuple_GET_SIZE(bases);
winner = metatype;
for (i = 0; i < nbases; i++) {
tmp = PyTuple_GET_ITEM(bases, i);
tmptype = Py_TYPE(tmp);
if (PyType_IsSubtype(winner, tmptype))
continue;
if (PyType_IsSubtype(tmptype, winner)) {
winner = tmptype;
continue;
}
PyErr_SetString(PyExc_TypeError,
"metaclass conflict: "
"the metaclass of a derived class "
"must be a (non-strict) subclass "
"of the metaclasses of all its bases");
/* Determine the proper metatype to deal with this: */
winner = _PyType_CalculateMetaclass(metatype, bases);
if (winner == NULL) {
return NULL;
}
if (winner != metatype) {
if (winner->tp_new != type_new) /* Pass it to the winner */
return winner->tp_new(winner, args, kwds);
@ -1984,6 +2004,7 @@ type_new(PyTypeObject *metatype, PyObject *args, PyObject *kwds)
}
/* Adjust for empty tuple bases */
nbases = PyTuple_GET_SIZE(bases);
if (nbases == 0) {
bases = PyTuple_Pack(1, &PyBaseObject_Type);
if (bases == NULL)

30
Python/bltinmodule.c
View File

@ -35,9 +35,10 @@ int Py_HasFileSystemDefaultEncoding = 1;
static PyObject *
builtin___build_class__(PyObject *self, PyObject *args, PyObject *kwds)
{
PyObject *func, *name, *bases, *mkw, *meta, *prep, *ns, *cell;
PyObject *func, *name, *bases, *mkw, *meta, *winner, *prep, *ns, *cell;
PyObject *cls = NULL;
Py_ssize_t nargs, nbases;
int isclass;
assert(args != NULL);
if (!PyTuple_Check(args)) {
@ -82,17 +83,42 @@ builtin___build_class__(PyObject *self, PyObject *args, PyObject *kwds)
Py_DECREF(bases);
return NULL;
}
/* metaclass is explicitly given, check if it's indeed a class */
isclass = PyType_Check(meta);
}
}
if (meta == NULL) {
if (PyTuple_GET_SIZE(bases) == 0)
/* if there are no bases, use type: */
if (PyTuple_GET_SIZE(bases) == 0) {
meta = (PyObject *) (&PyType_Type);
}
/* else get the type of the first base */
else {
PyObject *base0 = PyTuple_GET_ITEM(bases, 0);
meta = (PyObject *) (base0->ob_type);
}
Py_INCREF(meta);
isclass = 1; /* meta is really a class */
}
if (isclass) {
/* meta is really a class, so check for a more derived
metaclass, or possible metaclass conflicts: */
winner = (PyObject *)_PyType_CalculateMetaclass((PyTypeObject *)meta,
bases);
if (winner == NULL) {
Py_DECREF(meta);
Py_XDECREF(mkw);
Py_DECREF(bases);
return NULL;
}
if (winner != meta) {
Py_DECREF(meta);
meta = winner;
Py_INCREF(meta);
}
}
/* else: meta is not a class, so we cannot do the metaclass
calculation, so we will use the explicitly given object as it is */
prep = PyObject_GetAttrString(meta, "__prepare__");
if (prep == NULL) {
if (PyErr_ExceptionMatches(PyExc_AttributeError)) {