When getting a state event also include the previous content

synapse/api/events/__init__.py

@@ -157,6 +157,11 @@ class SynapseEvent(JsonEncodedObject):
 
 
 class SynapseStateEvent(SynapseEvent):
+
+    valid_keys = SynapseEvent.valid_keys + [
+        "prev_content",
+    ]
+
     def __init__(self, **kwargs):
         if "state_key" not in kwargs:
             kwargs["state_key"] = ""

synapse/storage/__init__.py

@@ -81,7 +81,7 @@ class DataStore(RoomMemberStore, RoomStore,
         defer.returnValue(latest)
 
     @defer.inlineCallbacks
-    def get_event(self, event_id):
+    def get_event(self, event_id, allow_none=False):
         events_dict = yield self._simple_select_one(
             "events",
             {"event_id": event_id},
@@ -92,8 +92,12 @@ class DataStore(RoomMemberStore, RoomStore,
                 "content",
                 "unrecognized_keys"
             ],
+            allow_none=allow_none,
         )
 
+        if not events_dict:
+            defer.returnValue(None)
+
         event = self._parse_event_from_row(events_dict)
         defer.returnValue(event)
 
@@ -220,7 +224,8 @@ class DataStore(RoomMemberStore, RoomStore,
 
         results = yield self._execute_and_decode(sql, *args)
 
-        defer.returnValue([self._parse_event_from_row(r) for r in results])
+        events = yield self._parse_events(results)
+        defer.returnValue(events)
 
     @defer.inlineCallbacks
     def _get_min_token(self):

synapse/storage/_base.py

@@ -312,6 +312,25 @@ class SQLBaseStore(object):
             **d
         )
 
+    def _parse_events(self, rows):
+        return self._db_pool.runInteraction(self._parse_events_txn, rows)
+
+    def _parse_events_txn(self, txn, rows):
+        events = [self._parse_event_from_row(r) for r in rows]
+
+        sql = "SELECT * FROM events WHERE event_id = ?"
+
+        for ev in events:
+           if hasattr(ev, "prev_state"):
+                # Load previous state_content. 
+                # TODO: Should we be pulling this out above?
+                cursor = txn.execute(sql, (ev.prev_state,))
+                prevs = self.cursor_to_dict(cursor)
+                if prevs:
+                    prev = self._parse_event_from_row(prevs[0])
+                    ev.prev_content = prev.content
+
+        return events
 
 class Table(object):
     """ A base class used to store information about a particular table.

synapse/storage/roommember.py

@@ -88,7 +88,7 @@ class RoomMemberStore(SQLBaseStore):
         txn.execute(sql, (user_id, room_id))
         rows = self.cursor_to_dict(txn)
         if rows:
-            return self._parse_event_from_row(rows[0])
+            return self._parse_events_txn(txn, rows)[0]
         else:
             return None
 
@@ -161,7 +161,7 @@ class RoomMemberStore(SQLBaseStore):
 
         # logger.debug("_get_members_query Got rows %s", rows)
 
-        results = [self._parse_event_from_row(r) for r in rows]
+        results = yield self._parse_events(rows)
         defer.returnValue(results)
 
     @defer.inlineCallbacks

synapse/storage/stream.py

@@ -188,7 +188,7 @@ class StreamStore(SQLBaseStore):
             user_id, user_id, from_id, to_id
         )
 
-        ret = [self._parse_event_from_row(r) for r in rows]
+        ret = yield self._parse_events(rows)
 
         if rows:
             key = "s%d" % max([r["stream_ordering"] for r in rows])
@@ -243,9 +243,11 @@ class StreamStore(SQLBaseStore):
             # TODO (erikj): We should work out what to do here instead.
             next_token = to_key if to_key else from_key
 
+        events = yield self._parse_events(rows)
+
         defer.returnValue(
             (
-                [self._parse_event_from_row(r) for r in rows],
+                events,
                 next_token
             )
         )
@@ -277,12 +279,11 @@ class StreamStore(SQLBaseStore):
         else:
             token = (end_token, end_token)
 
-        defer.returnValue(
+        events = yield self._parse_events(rows)
-            (
+
-                [self._parse_event_from_row(r) for r in rows],
+        ret = (events, token)
-                token
+
-            )
+        defer.returnValue(ret)
-        )
 
     def get_room_events_max_id(self):
         return self._db_pool.runInteraction(self._get_room_events_max_id_txn)