Change issubclass() so that recursive tuples (directly or indirectly

containing class objects) are allowed as the second argument.
This makes issubclass() more similar to isinstance() where recursive
tuples are allowed too.

3 files changed, 24 insertions, 6 deletions

diff --git a/Lib/test/test_isinstance.py b/Lib/test/test_isinstance.py
index 1bb09a6..5a19387 100644
--- a/Lib/test/test_isinstance.py
+++ b/Lib/test/test_isinstance.py
@@ -165,6 +165,13 @@ class Super:
 class Child(Super):
     pass
 
+# new-style classes
+class NewSuper(object):
+    pass
+
+class NewChild(NewSuper):
+    pass
+
 
 
 class TestIsInstanceIsSubclass(unittest.TestCase):
@@ -225,7 +232,17 @@ class TestIsInstanceIsSubclass(unittest.TestCase):
         self.assertEqual(False, issubclass(Super, (Child,)))
         self.assertEqual(True, issubclass(Super, (Child, Super)))
         self.assertEqual(False, issubclass(Child, ()))
-        self.assertRaises(TypeError, issubclass, Child, ((Child,),))
+        self.assertEqual(True, issubclass(Super, (Child, (Super,))))
+
+        self.assertEqual(True, issubclass(NewChild, (NewChild,)))
+        self.assertEqual(True, issubclass(NewChild, (NewSuper,)))
+        self.assertEqual(False, issubclass(NewSuper, (NewChild,)))
+        self.assertEqual(True, issubclass(NewSuper, (NewChild, NewSuper)))
+        self.assertEqual(False, issubclass(NewChild, ()))
+        self.assertEqual(True, issubclass(NewSuper, (NewChild, (NewSuper,))))
+
+        self.assertEqual(True, issubclass(int, (long, (float, int))))
+        self.assertEqual(True, issubclass(str, (unicode, (Child, NewChild, basestring))))
 
 
 
diff --git a/Objects/abstract.c b/Objects/abstract.c
index 47d2f31..8389774 100644
--- a/Objects/abstract.c
+++ b/Objects/abstract.c
@@ -2021,11 +2021,11 @@ PyObject_IsSubclass(PyObject *derived, PyObject *cls)
 			int i;
 			int n = PyTuple_GET_SIZE(cls);
 			for (i = 0; i < n; ++i) {
-				if (!check_class(PyTuple_GET_ITEM(cls, i),
-						"issubclass() arg 2 must be a class"
-						" or tuple of classes"))
-					return -1;
+				retval = PyObject_IsSubclass(derived, PyTuple_GET_ITEM(cls, i));
+				if (retval != 0) /* either found it, or got an error */
+					return retval;
 			}
+			return 0;
 		}
 		else {
 			if (!check_class(cls,
diff --git a/Objects/classobject.c b/Objects/classobject.c
index f3b9873..5234a65 100644
--- a/Objects/classobject.c
+++ b/Objects/classobject.c
@@ -490,9 +490,10 @@ PyClass_IsSubclass(PyObject *class, PyObject *base)
 	if (PyTuple_Check(base)) {
 		n = PyTuple_GET_SIZE(base);
 		for (i = 0; i < n; i++) {
-			if (class == PyTuple_GET_ITEM(base, i))
+			if (PyClass_IsSubclass(class, PyTuple_GET_ITEM(base, i)))
 				return 1;
 		}
+		return 0;
 	}
 	if (class == NULL || !PyClass_Check(class))
 		return 0;