Conditionally apply monkey patch so we work with ZODB4

relstorage/__init__.py

@@ -29,35 +29,39 @@ def check_compatible():
 
 check_compatible()
 
+try:
+    import ZODB.mvccadapter # check or ZODB5, which doesn't need the patch
+except ImportError:
 
-# def patch_zodb_sync():
-#     """Patch Connection.sync() and afterCompletion() to pass the 'force' flag.
-#     """
-
-#     def _storage_sync(self, *ignored, **kw):
-#         if hasattr(self, '_readCurrent'):
-#             self._readCurrent.clear()
-#         sync = getattr(self._storage, 'sync', 0)
-#         if sync:
-#             # By default, do not force the sync, allowing RelStorage
-#             # to ignore sync requests for a while.
-#             force = kw.get('force', False)
-#             try:
-#                 sync(force=force)
-#             except TypeError:
-#                 # The 'force' parameter is not accepted.
-#                 sync()
-#         self._flush_invalidations()
-
-#     def sync(self):
-#         """Manually update the view on the database."""
-#         self.transaction_manager.abort()
-#         self._storage_sync(force=True)
-
-#     from ZODB.Connection import Connection
-#     Connection._storage_sync = _storage_sync
-#     Connection.afterCompletion = _storage_sync
-#     Connection.newTransaction = _storage_sync
-#     Connection.sync = sync
-
-# patch_zodb_sync()
+    def patch_zodb_sync():
+        """Patch Connection.sync() and afterCompletion()
+        to pass the 'force' flag.
+        """
+
+        def _storage_sync(self, *ignored, **kw):
+            if hasattr(self, '_readCurrent'):
+                self._readCurrent.clear()
+            sync = getattr(self._storage, 'sync', 0)
+            if sync:
+                # By default, do not force the sync, allowing RelStorage
+                # to ignore sync requests for a while.
+                force = kw.get('force', False)
+                try:
+                    sync(force=force)
+                except TypeError:
+                    # The 'force' parameter is not accepted.
+                    sync()
+            self._flush_invalidations()
+
+        def sync(self):
+            """Manually update the view on the database."""
+            self.transaction_manager.abort()
+            self._storage_sync(force=True)
+
+        from ZODB.Connection import Connection
+        Connection._storage_sync = _storage_sync
+        Connection.afterCompletion = _storage_sync
+        Connection.newTransaction = _storage_sync
+        Connection.sync = sync
+
+    patch_zodb_sync()