Issue #26482: Allowed pickling recursive dequeues.

Lib/test/test_deque.py

@@ -622,20 +622,22 @@ class TestBasic(unittest.TestCase):
         self.assertEqual(list(d), list(e))
 
     def test_pickle(self):
-        d = deque(range(200))
+        for d in deque(range(200)), deque(range(200), 100):
             for i in range(pickle.HIGHEST_PROTOCOL + 1):
                 s = pickle.dumps(d, i)
                 e = pickle.loads(s)
-            self.assertNotEqual(id(d), id(e))
-            self.assertEqual(list(d), list(e))
+                self.assertNotEqual(id(e), id(d))
+                self.assertEqual(list(e), list(d))
+                self.assertEqual(e.maxlen, d.maxlen)
 
-##    def test_pickle_recursive(self):
-##        d = deque('abc')
-##        d.append(d)
-##        for i in range(pickle.HIGHEST_PROTOCOL + 1):
-##            e = pickle.loads(pickle.dumps(d, i))
-##            self.assertNotEqual(id(d), id(e))
-##            self.assertEqual(id(e), id(e[-1]))
+    def test_pickle_recursive(self):
+        for d in deque('abc'), deque('abc', 3):
+            d.append(d)
+            for i in range(pickle.HIGHEST_PROTOCOL + 1):
+                e = pickle.loads(pickle.dumps(d, i))
+                self.assertNotEqual(id(e), id(d))
+                self.assertEqual(id(e[-1]), id(e))
+                self.assertEqual(e.maxlen, d.maxlen)
 
     def test_iterator_pickle(self):
         data = deque(range(200))
@@ -827,24 +829,26 @@ class TestSubclass(unittest.TestCase):
             self.assertEqual(type(d), type(e))
             self.assertEqual(list(d), list(e))
 
-##    def test_pickle(self):
-##        d = Deque('abc')
-##        d.append(d)
-##
-##        e = pickle.loads(pickle.dumps(d))
-##        self.assertNotEqual(id(d), id(e))
-##        self.assertEqual(type(d), type(e))
-##        dd = d.pop()
-##        ee = e.pop()
-##        self.assertEqual(id(e), id(ee))
-##        self.assertEqual(d, e)
-##
-##        d.x = d
-##        e = pickle.loads(pickle.dumps(d))
-##        self.assertEqual(id(e), id(e.x))
-##
-##        d = DequeWithBadIter('abc')
-##        self.assertRaises(TypeError, pickle.dumps, d)
+    def test_pickle_recursive(self):
+        for proto in range(pickle.HIGHEST_PROTOCOL + 1):
+            for d in Deque('abc'), Deque('abc', 3):
+                d.append(d)
+
+                e = pickle.loads(pickle.dumps(d, proto))
+                self.assertNotEqual(id(e), id(d))
+                self.assertEqual(type(e), type(d))
+                self.assertEqual(e.maxlen, d.maxlen)
+                dd = d.pop()
+                ee = e.pop()
+                self.assertEqual(id(ee), id(e))
+                self.assertEqual(e, d)
+
+                d.x = d
+                e = pickle.loads(pickle.dumps(d, proto))
+                self.assertEqual(id(e.x), id(e))
+
+            for d in DequeWithBadIter('abc'), DequeWithBadIter('abc', 2):
+                self.assertRaises(TypeError, pickle.dumps, d, proto)
 
     def test_weakref(self):
         d = deque('gallahad')

Misc/NEWS

@@ -201,6 +201,8 @@ Core and Builtins
 Library
 -------
 
+- Issue #26482: Allowed pickling recursive dequeues.
+
 - Issue #26335: Make mmap.write() return the number of bytes written like
   other write methods.  Patch by Jakub Stasiak.
 

Modules/_collectionsmodule.c

@@ -1296,31 +1296,31 @@ deque_traverse(dequeobject *deque, visitproc visit, void *arg)
 static PyObject *
 deque_reduce(dequeobject *deque)
 {
-    PyObject *dict, *result, *aslist;
+    PyObject *dict, *it;
     _Py_IDENTIFIER(__dict__);
 
     dict = _PyObject_GetAttrId((PyObject *)deque, &PyId___dict__);
-    if (dict == NULL)
+    if (dict == NULL) {
+        if (!PyErr_ExceptionMatches(PyExc_AttributeError)) {
+            return NULL;
+        }
         PyErr_Clear();
-    aslist = PySequence_List((PyObject *)deque);
-    if (aslist == NULL) {
-        Py_XDECREF(dict);
+        dict = Py_None;
+        Py_INCREF(dict);
+    }
+
+    it = PyObject_GetIter((PyObject *)deque);
+    if (it == NULL) {
+        Py_DECREF(dict);
         return NULL;
     }
-    if (dict == NULL) {
-        if (deque->maxlen < 0)
-            result = Py_BuildValue("O(O)", Py_TYPE(deque), aslist);
-        else
-            result = Py_BuildValue("O(On)", Py_TYPE(deque), aslist, deque->maxlen);
-    } else {
-        if (deque->maxlen < 0)
-            result = Py_BuildValue("O(OO)O", Py_TYPE(deque), aslist, Py_None, dict);
-        else
-            result = Py_BuildValue("O(On)O", Py_TYPE(deque), aslist, deque->maxlen, dict);
+
+    if (deque->maxlen < 0) {
+        return Py_BuildValue("O()NN", Py_TYPE(deque), dict, it);
+    }
+    else {
+        return Py_BuildValue("O(()n)NN", Py_TYPE(deque), deque->maxlen, dict, it);
     }
-    Py_XDECREF(dict);
-    Py_DECREF(aslist);
-    return result;
 }
 
 PyDoc_STRVAR(reduce_doc, "Return state information for pickling.");