Refined interfaces to distinguish between data-manager savepoints and

transaction savepoints.

Updated some interface declarations.

src/ZODB/Connection.py

@@ -27,7 +27,7 @@ from persistent import PickleCache
 # interfaces
 from persistent.interfaces import IPersistentDataManager
 from ZODB.interfaces import IConnection
-from transaction.interfaces import IDataManager
+from transaction.interfaces import ISavepointDataManager, IDataManagerSavepoint
 from zope.interface import implements
 
 import transaction
@@ -59,7 +59,7 @@ def resetCaches():
 class Connection(ExportImport, object):
     """Connection to ZODB for loading and storing objects."""
 
-    implements(IConnection, IDataManager, IPersistentDataManager)
+    implements(IConnection, ISavepointDataManager, IPersistentDataManager)
 
     _storage = _normal_storage = _savepoint_storage = None
 
@@ -319,7 +319,7 @@ class Connection(ExportImport, object):
     ##########################################################################
 
     ##########################################################################
-    # Data manager (IDataManager) methods
+    # Data manager (ISavepointDataManager) methods
 
     def abort(self, transaction):
         """Abort a transaction and forget all changes."""
@@ -638,7 +638,7 @@ class Connection(ExportImport, object):
         """Return a consistent sort key for this connection."""
         return "%s:%s" % (self._storage.sortKey(), id(self))
 
-    # Data manager (IDataManager) methods
+    # Data manager (ISavepointDataManager) methods
     ##########################################################################
 
     ##########################################################################
@@ -1061,6 +1061,8 @@ class Connection(ExportImport, object):
 
 class Savepoint:
 
+    implements(IDataManagerSavepoint)
+
     def __init__(self, datamanager, state):
         self.datamanager = datamanager
         self.state = state

src/transaction/interfaces.py

@@ -308,7 +308,25 @@ class IDataManager(zope.interface.Interface):
 class ISavepointDataManager(IDataManager):
 
     def savepoint():
-        """Return a savepoint (ISavepoint)
+        """Return a data-manager savepoint (IDataManagerSavepoint)
+        """
+
+class IDataManagerSavepoint(zope.interface.Interface):
+    """Savepoint for data-manager changes for use in transaction savepoints
+
+    Datamanager savepoints are used by, and only by, transaction savepoints.
+    
+    Note that data manager savepoints don't have any notion of or
+    responsibility for validity.  It isn't the responsibility of
+    data-manager savepoints to prevent multiple rollbacks or rollbacks
+    after transaction termination.  Preventing invalid savepoint
+    rollback is the responsibility of transaction rollbacks.
+    Application code should never use data-manager savepoints.
+    
+    """
+
+    def rollback():
+        """Rollback any work done since the savepoint
         """
 
 class ISavepoint(zope.interface.Interface):

src/transaction/tests/savepointsample.py

@@ -30,7 +30,7 @@ class SampleDataManager(UserDict.DictMixin):
     This data manager stores named simple values, like strings and numbers.
     """
     
-    interface.implements(transaction.interfaces.ISavepointDataManager)
+    interface.implements(transaction.interfaces.IDataManager)
 
     def __init__(self, transaction_manager = None):
         if transaction_manager is None:
@@ -156,6 +156,8 @@ class SampleSavepointDataManager(SampleDataManager):
     This extends the basic data manager with savepoint support.
     """
 
+    interface.implements(transaction.interfaces.ISavepointDataManager)
+
     def savepoint(self):
         # When we create the savepoint, we save the existing database state
         return SampleSavepoint(self, self.uncommitted.copy())
@@ -166,6 +168,8 @@ class SampleSavepointDataManager(SampleDataManager):
 
 class SampleSavepoint:
 
+    interface.implements(transaction.interfaces.IDataManagerSavepoint)
+
     def __init__(self, data_manager, data):
         self.data_manager = data_manager
         self.data = data