Merge with 3.3.

Lib/test/pickletester.py

@@ -1785,30 +1785,34 @@ class AbstractPersistentPicklerTests(unittest.TestCase):
         if isinstance(object, int) and object % 2 == 0:
             self.id_count += 1
             return str(object)
+        elif object == "test_false_value":
+            self.false_count += 1
+            return ""
         else:
             return None
 
     def persistent_load(self, oid):
-        self.load_count += 1
-        object = int(oid)
-        assert object % 2 == 0
-        return object
+        if not oid:
+            self.load_false_count += 1
+            return "test_false_value"
+        else:
+            self.load_count += 1
+            object = int(oid)
+            assert object % 2 == 0
+            return object
 
     def test_persistence(self):
-        self.id_count = 0
-        self.load_count = 0
-        L = list(range(10))
-        self.assertEqual(self.loads(self.dumps(L)), L)
-        self.assertEqual(self.id_count, 5)
-        self.assertEqual(self.load_count, 5)
-
-    def test_bin_persistence(self):
-        self.id_count = 0
-        self.load_count = 0
-        L = list(range(10))
-        self.assertEqual(self.loads(self.dumps(L, 1)), L)
-        self.assertEqual(self.id_count, 5)
-        self.assertEqual(self.load_count, 5)
+        L = list(range(10)) + ["test_false_value"]
+        for proto in protocols:
+            self.id_count = 0
+            self.false_count = 0
+            self.load_false_count = 0
+            self.load_count = 0
+            self.assertEqual(self.loads(self.dumps(L, proto)), L)
+            self.assertEqual(self.id_count, 5)
+            self.assertEqual(self.false_count, 1)
+            self.assertEqual(self.load_count, 5)
+            self.assertEqual(self.load_false_count, 1)
 
 
 class AbstractPicklerUnpicklerObjectTests(unittest.TestCase):

Misc/NEWS

@@ -30,6 +30,9 @@ Library
 - Issue #19698: Removed exec_module() methods from
   importlib.machinery.BuiltinImporter and ExtensionFileLoader.
 
+- Fixed _pickle.Unpickler to not fail when loading empty strings as
+  persistent IDs.
+
 - ssl.create_default_context() sets OP_NO_COMPRESSION to prevent CRIME.
 
 - Issue #19802: Add socket.SO_PRIORITY.

Modules/_pickle.c

@@ -5355,7 +5355,7 @@ load_persid(UnpicklerObject *self)
     if (self->pers_func) {
         if ((len = _Unpickler_Readline(self, &s)) < 0)
             return -1;
-        if (len < 2)
+        if (len < 1)
             return bad_readline();
 
         pid = PyBytes_FromStringAndSize(s, len - 1);