IStorage: simplify the API of store/tpc_finish to notify of resolved conflicts

src/ZODB/ConflictResolution.py

@@ -28,7 +28,7 @@ from pickle import PicklingError
 
 logger = logging.getLogger('ZODB.ConflictResolution')
 
-ResolvedSerial = b'rs'
+ResolvedSerial = b'rs' # deprecated: store/tpc_finish should just use True
 
 class BadClassName(Exception):
     pass

src/ZODB/Connection.py

@@ -705,7 +705,7 @@ class Connection(ExportImport, object):
 
             self._handle_serial(oid, s)
 
-    def _handle_serial(self, oid, serial, change=True):
+    def _handle_serial(self, oid, serial=True, change=True):
 
         # if we write an object, we don't want to check if it was read
         # while current.  This is a convenient choke point to do this.
@@ -713,7 +713,9 @@ class Connection(ExportImport, object):
 
         if not serial:
             return
-        if not isinstance(serial, bytes):
+        if serial is True:
+            serial = ResolvedSerial
+        elif not isinstance(serial, bytes):
             raise serial
         obj = self._cache.get(oid, None)
         if obj is None:
@@ -721,6 +723,7 @@ class Connection(ExportImport, object):
         if serial == ResolvedSerial:
             del obj._p_changed # transition from changed to ghost
         else:
+            self._warn_about_returned_serial()
             if change:
                 obj._p_changed = 0 # transition from changed to up-to-date
             obj._p_serial = serial
@@ -790,6 +793,11 @@ class Connection(ExportImport, object):
             raise
 
         if s:
+            if type(s[0]) is bytes:
+                for oid in s:
+                    self._handle_serial(oid)
+                return
+            self._warn_about_returned_serial()
             for oid, serial in s:
                 self._handle_serial(oid, serial)
 
@@ -829,9 +837,9 @@ class Connection(ExportImport, object):
             self._warn_about_returned_serial = lambda: None
         else:
             warnings.warn(
-                "In ZODB 5+, it will be required for tpc_finish to return the"
-                " committed tid. store/tpc_vote will only have to notify about"
-                " resolved conflicts.",
+                "In ZODB 5+, the new API for the returned value of"
+                " store/tpc_vote/tpc_finish will be mandatory."
+                " See IStorage for more information.",
                 DeprecationWarning, 2)
             Connection._warn_about_returned_serial = lambda self: None
 

src/ZODB/interfaces.py

@@ -797,13 +797,14 @@ class IStorage(Interface):
         without an error, then there must not be an error if
         tpc_finish or tpc_abort is called subsequently.
 
-        The return value can be either None or a sequence of object-id
-        and serial pairs giving new serials for objects who's ids were
-        passed to previous store calls in the same transaction.
-
-        A serial returned in a sequence of oid/serial pairs, may be
-        the special value ZODB.ConflictResolution.ResolvedSerial to
-        indicate that a conflict occured and that the object should be
+        The return value can be either None or a sequence of oids for which
+        a conflict was resolved.
+
+        For compatibility, the return value can also be a sequence of object-id
+        and serial pairs giving new serials for objects whose ids were
+        passed to previous store calls in the same transaction. The serial
+        can be the special value ZODB.ConflictResolution.ResolvedSerial to
+        indicate that a conflict occurred and that the object should be
         invalidated.
 
         After the tpc_vote call, all solved conflicts must have been notified,

src/ZODB/tests/testDemoStorage.py

@@ -58,8 +58,8 @@ class DemoStorage(ZODB.DemoStorage.DemoStorage):
             assert type(s) is bytes, s
             return
         if not self.delayed_store:
-            return s
-        self.__stored.append((oid, s))
+            return True
+        self.__stored.append(oid)
 
     tpc_vote = property(lambda self: self._tpc_vote, lambda *_: None)