Make deleting the _p_jar of a pure-Python persistent object work like the C version.

CHANGES.rst

 ``persistent`` Changelog
 ========================
 
+4.0.8 (Unreleased)
+------------------
+
+- Make it possible to delete the ``_p_jar`` of a pure-Python
+  ``Persistent`` object (fixes aborting a ZODB Connection that
+  has added objects).
 
 4.0.7 (2014-02-20)
 ------------------

persistent/persistence.py

@@ -72,7 +72,16 @@ class Persistent(object):
             self.__jar = value
             self.__flags = 0
 
-    _p_jar = property(_get_jar, _set_jar)
+    def _del_jar(self):
+        jar = self.__jar
+        oid = self.__oid
+        if jar is not None:
+            if oid and jar._cache.get(oid):
+                raise ValueError("can't delete _p_jar of cached object")
+            self.__setattr__('_Persistent__jar', None)
+            self.__flags = None
+
+    _p_jar = property(_get_jar, _set_jar, _del_jar)
 
     # _p_oid:  see IPersistent.
     def _get_oid(self):

persistent/tests/test_persistence.py

@@ -86,6 +86,24 @@ class _Persistent_Base(object):
         self.assertEqual(inst._p_sticky, False)
         self.assertEqual(inst._p_status, 'unsaved')
 
+    def test_cannot_del_jar_while_in_cache(self):
+        inst, _, OID = self._makeOneWithJar()
+        def _test():
+            del inst._p_jar
+        self.assertRaises(ValueError, _test)
+
+    def test_del_jar_oid_like_ZODB_abort(self):
+        # When a ZODB connection aborts,
+		# it removes registered objects from the cache,
+		# deletes their jar, deletes their OID
+		# and finally sets p_changed to false
+        inst, jar, OID = self._makeOneWithJar()
+        del jar._cache[OID]
+        del inst._p_jar
+        self.assertEqual(inst._p_jar, None)
+        del inst._p_oid
+        self.assertEqual(inst._p_oid, None)
+
     def test_assign_p_jar_w_new_jar(self):
         inst, jar, OID = self._makeOneWithJar()
         new_jar = self._makeJar()
@@ -1314,11 +1332,17 @@ class PyPersistentTests(unittest.TestCase, _Persistent_Base):
             def __init__(self, jar):
                 self._jar = jar
                 self._mru = []
+                self._data = {}
             def mru(self, oid):
                 self._mru.append(oid)
             def new_ghost(self, oid, obj):
                 obj._p_jar = self._jar
                 obj._p_oid = oid
+                self._data[oid] = obj
+            def get(self, oid):
+                return self._data.get(oid)
+            def __delitem__(self, oid):
+                del self._data[oid]
 
         return _Cache(jar)