Merge pull request #132 from zopefoundation/data-for-TransactionMetaD…

…ata-and-TransactionRecord

Fixed: ZODB.Connection.TransactionMetaData didn't custom data

CHANGES.rst

@@ -2,6 +2,9 @@
  Change History
 ================
 
+- Fixed: ``ZODB.Connection.TransactionMetaData`` didn't support custom data
+  storage that some storages rely on.
+
 5.1.0 (2016-11-17)
 ==================
 

src/ZODB/BaseStorage.py

@@ -28,14 +28,13 @@
 
 import ZODB.interfaces
 from . import POSException, utils
+from .Connection import TransactionMetaData
 from .utils import z64, oid_repr, byte_ord, byte_chr, load_current
 from .UndoLogCompatible import UndoLogCompatible
 from ._compat import dumps, _protocol, py2_hasattr
 
 log = logging.getLogger("ZODB.BaseStorage")
 
-
-
 class BaseStorage(UndoLogCompatible):
     """Base class that supports storage implementations.
 
@@ -359,25 +358,14 @@ def checkCurrentSerialInTransaction(self, oid, serial, transaction):
 BaseStorage.checkCurrentSerialInTransaction = checkCurrentSerialInTransaction
 
 @zope.interface.implementer(ZODB.interfaces.IStorageTransactionInformation)
-class TransactionRecord(object):
+class TransactionRecord(TransactionMetaData):
     """Abstract base class for iterator protocol"""
 
 
     def __init__(self, tid, status, user, description, extension):
         self.tid = tid
         self.status = status
-        self.user = user
-        self.description = description
-        self.extension = extension
-
-    # XXX This is a workaround to make the TransactionRecord compatible with a
-    # transaction object because it is passed to tpc_begin().
-    def _ext_set(self, value):
-        self.extension = value
-    def _ext_get(self):
-        return self.extension
-    _extension = property(fset=_ext_set, fget=_ext_get)
-
+        TransactionMetaData.__init__(self, user, description, extension)
 
 @zope.interface.implementer(ZODB.interfaces.IStorageRecordInformation)
 class DataRecord(object):

src/ZODB/Connection.py

@@ -1321,3 +1321,17 @@ def _extension(self):
     @_extension.setter
     def _extension(self, v):
         self.extension = v
+
+    def data(self, ob):
+        try:
+            return self._data[id(ob)]
+        except (AttributeError, KeyError):
+            raise KeyError(ob)
+
+    def set_data(self, ob, ob_data):
+        try:
+            data = self._data
+        except AttributeError:
+            data = self._data = {}
+
+        data[id(ob)] = ob_data

src/ZODB/interfaces.py

@@ -546,6 +546,28 @@ class IStorageTransactionMetaData(Interface):
     extension = Attribute(
         "A dictionary carrying a transaction's extended_info data")
 
+
+    def set_data(ob, data):
+        """Hold data on behalf of an object
+
+        For objects such as storages that
+        work with multiple transactions, it's convenient to store
+        transaction-specific data on the transaction itself.  The
+        transaction knows nothing about the data, but simply holds it
+        on behalf of the object.
+
+        The object passed should be the object that needs the data, as
+        opposed to simple object like a string. (Internally, the id of
+        the object is used as the key.)
+        """
+
+    def data(ob):
+        """Retrieve data held on behalf of an object.
+
+        See set_data.
+        """
+
+
 class IStorage(Interface):
     """A storage is responsible for storing and retrieving data of objects.
 

src/ZODB/tests/test_TransactionMetaData.py

@@ -87,6 +87,23 @@ def tpc_begin(self, transaction):
         self.assertEqual(t.description, b'description\xc2\x80')
         self.assertEqual(t.extension, dict(foo='FOO'))
 
+    def test_data(self):
+        t = TransactionMetaData()
+
+        # Can't get data that wasn't set:
+        with self.assertRaises(KeyError) as c:
+            t.data(self)
+        self.assertEqual(c.exception.args, (self,))
+
+        data = dict(a=1)
+        t.set_data(self, data)
+        self.assertEqual(t.data(self), data)
+
+        # Can't get something we haven't stored.
+        with self.assertRaises(KeyError) as c:
+            t.data(data)
+        self.assertEqual(c.exception.args, (data,))
+
 def test_suite():
     return unittest.makeSuite(TransactionMetaDataTests)