backport r67246 from the trunk

Lib/test/test_descr.py

@@ -1073,12 +1073,7 @@ def consistency_with_epg():
           (EditableScrollablePane, ScrollablePane, EditablePane,
            Pane, ScrollingMixin, EditingMixin, object))
 
-mro_err_msg = """Cannot create a consistent method resolution
-order (MRO) for bases """
-
-def mro_disagreement():
-    if verbose: print "Testing error messages for MRO disagreement..."
-    def raises(exc, expected, callable, *args):
+def raises(exc, expected, callable, *args):
     try:
         callable(*args)
     except exc, msg:
@@ -1087,6 +1082,12 @@ def mro_disagreement():
                                                            expected)
     else:
         raise TestFailed, "Expected %s" % exc
+
+mro_err_msg = """Cannot create a consistent method resolution
+order (MRO) for bases """
+
+def mro_disagreement():
+    if verbose: print "Testing error messages for MRO disagreement..."
     class A(object): pass
     class B(A): pass
     class C(object): pass
@@ -4171,6 +4172,45 @@ def methodwrapper():
     vereq(t.__add__, (7,).__add__)
     vereq(hash(t.__add__), hash((7,).__add__))
 
+def test_getattr_hooks():
+    # issue 4230
+    class Descriptor(object):
+        counter = 0
+        def __get__(self, obj, objtype=None):
+            def getter(name):
+                self.counter += 1
+                raise AttributeError(name)
+            return getter
+
+    descr = Descriptor()
+    class A(object):
+        __getattribute__ = descr
+    class B(object):
+        __getattr__ = descr
+    class C(object):
+        __getattribute__ = descr
+        __getattr__ = descr
+
+    raises(AttributeError, "attr", getattr, A(), "attr")
+    vereq(descr.counter, 1)
+    raises(AttributeError, "attr", getattr, B(), "attr")
+    vereq(descr.counter, 2)
+    raises(AttributeError, "attr", getattr, C(), "attr")
+    vereq(descr.counter, 4)
+
+    import gc
+    class EvilGetattribute(object):
+        # This used to segfault
+        def __getattr__(self, name):
+            raise AttributeError(name)
+        def __getattribute__(self, name):
+            del EvilGetattribute.__getattr__
+            for i in range(5):
+                gc.collect()
+            raise AttributeError(name)
+
+    raises(AttributeError, "attr", getattr, EvilGetattribute(), "attr")
+
 def notimplemented():
     # all binary methods should be able to return a NotImplemented
     if verbose:
@@ -4352,6 +4392,7 @@ def test_main():
     methodwrapper()
     notimplemented()
     test_assign_slice()
+    test_getattr_hooks()
 
     if verbose: print "All OK"
 

Misc/NEWS

@@ -12,6 +12,8 @@ What's New in Python 2.5.3?
 Core and builtins
 -----------------
 
+- Issue #4230: If ``__getattr__`` is a descriptor, it now functions correctly.
+
 - Issue #4048: The parser module now correctly validates relative imports.
 
 - Issue #4176: Fixed a crash when pickling an object which ``__reduce__``

Objects/typeobject.c

@@ -4737,6 +4737,24 @@ slot_tp_getattro(PyObject *self, PyObject *name)
 			   "(O)", name);
 }
 
+static PyObject *
+call_attribute(PyObject *self, PyObject *attr, PyObject *name)
+{
+	PyObject *res, *descr = NULL;
+	descrgetfunc f = attr->ob_type->tp_descr_get;
+
+	if (f != NULL) {
+		descr = f(attr, self, (PyObject *)(self->ob_type));
+		if (descr == NULL)
+			return NULL;
+		else
+			attr = descr;
+	}
+	res = PyObject_CallFunctionObjArgs(attr, name, NULL);
+	Py_XDECREF(descr);
+	return res;
+}
+
 static PyObject *
 slot_tp_getattr_hook(PyObject *self, PyObject *name)
 {
@@ -4756,24 +4774,39 @@ slot_tp_getattr_hook(PyObject *self, PyObject *name)
 		if (getattribute_str == NULL)
 			return NULL;
 	}
+	/* speed hack: we could use lookup_maybe, but that would resolve the
+	   method fully for each attribute lookup for classes with
+	   __getattr__, even when the attribute is present. So we use
+	   _PyType_Lookup and create the method only when needed, with
+	   call_attribute. */
 	getattr = _PyType_Lookup(tp, getattr_str);
 	if (getattr == NULL) {
 		/* No __getattr__ hook: use a simpler dispatcher */
 		tp->tp_getattro = slot_tp_getattro;
 		return slot_tp_getattro(self, name);
 	}
+	Py_INCREF(getattr);
+	/* speed hack: we could use lookup_maybe, but that would resolve the
+	   method fully for each attribute lookup for classes with
+	   __getattr__, even when self has the default __getattribute__
+	   method. So we use _PyType_Lookup and create the method only when
+	   needed, with call_attribute. */
 	getattribute = _PyType_Lookup(tp, getattribute_str);
 	if (getattribute == NULL ||
 	    (getattribute->ob_type == &PyWrapperDescr_Type &&
 	     ((PyWrapperDescrObject *)getattribute)->d_wrapped ==
 	     (void *)PyObject_GenericGetAttr))
 		res = PyObject_GenericGetAttr(self, name);
-	else
-		res = PyObject_CallFunctionObjArgs(getattribute, self, name, NULL);
+	else {
+		Py_INCREF(getattribute);
+		res = call_attribute(self, getattribute, name);
+		Py_DECREF(getattribute);
+	}
 	if (res == NULL && PyErr_ExceptionMatches(PyExc_AttributeError)) {
 		PyErr_Clear();
-		res = PyObject_CallFunctionObjArgs(getattr, self, name, NULL);
+		res = call_attribute(self, getattr, name);
 	}
+	Py_DECREF(getattr);
 	return res;
 }