Bugfix: Make sure you don't get events for rooms you've left

src/github.com/matrix-org/dendrite/cmd/syncserver-integration-tests/main.go

@@ -574,6 +574,25 @@ func main() {
 
 	// $ curl -XPUT -d '{"msgtype":"m.text","body":"why did you kick charlie"}' "http://localhost:8009/_matrix/client/r0/rooms/%21PjrbIMW2cIiaYF4t:localhost/send/m.room.message/3?access_token=@bob:localhost"
 	// $ curl -XPUT -d '{"name":"No Charlies"}' "http://localhost:8009/_matrix/client/r0/rooms/%21PjrbIMW2cIiaYF4t:localhost/state/m.room.name?access_token=@alice:localhost"
+	if err := exe.WriteToTopic(inputTopic, canonicalJSONInput(outputRoomEventTestData[17:19])); err != nil {
+		panic(err)
+	}
+	// Check that users don't see state changes in rooms after they have left
+	testSyncServer(syncServerCmdChan, "@charlie:localhost", "17", `{
+		"account_data": {
+			"events": []
+		},
+		"next_batch": "19",
+		"presence": {
+			"events": []
+		},
+		"rooms": {
+			"invite": {},
+			"join": {},
+			"leave": {}
+		}
+	}`)
+
 	// $ curl -XPUT -d '{"msgtype":"m.text","body":"whatever"}' "http://localhost:8009/_matrix/client/r0/rooms/%21PjrbIMW2cIiaYF4t:localhost/send/m.room.message/3?access_token=@bob:localhost"
 	// $ curl -XPUT -d '{"membership":"leave"}' "http://localhost:8009/_matrix/client/r0/rooms/%21PjrbIMW2cIiaYF4t:localhost/state/m.room.member/@bob:localhost?access_token=@bob:localhost"
 	// $ curl -XPUT -d '{"msgtype":"m.text","body":"im alone now"}' "http://localhost:8009/_matrix/client/r0/rooms/%21PjrbIMW2cIiaYF4t:localhost/send/m.room.message/3?access_token=@alice:localhost"

src/github.com/matrix-org/dendrite/syncapi/storage/syncserver.go

@@ -232,27 +232,14 @@ func (d *SyncServerDatabase) getStateDeltas(txn *sql.Tx, fromPos, toPos types.St
 	//     * Check if user is still CURRENTLY invited to the room. If so, add room to 'invited' block.
 	//     * Check if the user is CURRENTLY (TODO) left/banned. If so, add room to 'archived' block.
 	// - Get all CURRENTLY joined rooms, and add them to 'joined' block.
+	var deltas []stateDelta
+
+	// get all the state events ever between these two positions
 	state, err := d.events.StateBetween(txn, fromPos, toPos)
 	if err != nil {
 		return nil, err
 	}
-
-	// Add in currently joined rooms which weren't already added (because no state changes for these rooms)
-	joinedRoomIDs, err := d.roomstate.SelectRoomIDsWithMembership(txn, userID, "join")
-	if err != nil {
-		return nil, err
-	}
-	for _, joinedRoomID := range joinedRoomIDs {
-		if len(state[joinedRoomID]) > 0 {
-			continue // we already have a state delta
-		}
-		// explicitly state there is a 0 delta using an empty array so it marshals as []
-		state[joinedRoomID] = []gomatrixserverlib.Event{}
-	}
-
-	var deltas []stateDelta
 	for roomID, stateEvents := range state {
-		var added bool
 		for _, ev := range stateEvents {
 			// TODO: Currently this will incorrectly add rooms which were ALREADY joined but they sent another no-op join event.
 			//       We should be checking if the user was already joined at fromPos and not proceed if so. As a result of this,
@@ -262,11 +249,13 @@ func (d *SyncServerDatabase) getStateDeltas(txn *sql.Tx, fromPos, toPos types.St
 			if membership := getMembershipFromEvent(&ev, userID); membership != "" {
 				if membership == "join" {
 					// send full room state down instead of a delta
-					allState, err := d.roomstate.CurrentState(txn, roomID)
+					var allState []gomatrixserverlib.Event
+					allState, err = d.roomstate.CurrentState(txn, roomID)
 					if err != nil {
 						return nil, err
 					}
-					stateEvents = allState
+					state[roomID] = allState
+					continue // we'll add this room in when we do joined rooms
 				}
 
 				deltas = append(deltas, stateDelta{
@@ -274,21 +263,23 @@ func (d *SyncServerDatabase) getStateDeltas(txn *sql.Tx, fromPos, toPos types.St
 					stateEvents: stateEvents,
 					roomID:      roomID,
 				})
-				added = true
 				break
 			}
 		}
-		if !added {
+	}
-			// We can hit this case if:
+
-			// - There is a 0 delta
+	// Add in currently joined rooms
-			// - There is a delta but it contains no membership changes
+	joinedRoomIDs, err := d.roomstate.SelectRoomIDsWithMembership(txn, userID, "join")
+	if err != nil {
+		return nil, err
+	}
+	for _, joinedRoomID := range joinedRoomIDs {
 		deltas = append(deltas, stateDelta{
 			membership:  "join",
-				roomID:      roomID,
+			stateEvents: state[joinedRoomID],
-				stateEvents: stateEvents,
+			roomID:      joinedRoomID,
 		})
 	}
-	}
 
 	return deltas, nil
 }