Support MSC4222 state_after (#4487)

* WIP support for state_after

* Fix sliding sync sdk / embedded tests

* Allow both state & state_after to be undefined

Since it must have allowed state to be undefined previously: the test
had it as such.

* Fix limited sync handling

* Need to use state_after being undefined

if state can be undefined anyway

* Make sliding sync sdk tests pass

* Remove deprecated interfaces & backwards-compat code

* Remove useless assignment

* Use updates unstable prefix

* Clarify docs

* Remove additional semi-backwards compatible overload

* Update unstable prefixes

* Iterate

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

* Iterate

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

* Fix test

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

* Iterate

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

* Iterate

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

* Add test for MSC4222 behaviour

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

* Improve coverage

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

* Iterate

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

* Fix tests

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

* Iterate

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

* Tidy

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

* Add comments to explain why things work as they are.

* Fix sync accumulator for state_after sync handling

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

* Add tests

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

* Revert "Fix room state being updated with old (now overwritten) state and emitting for those updates. (#4242)"

This reverts commit 957329b218.

* Fix Sync Accumulator toJSON putting start timeline state in state_after field

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

* Update tests

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

* Add test case

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

* Iterate

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

---------

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>
Co-authored-by: Hugh Nimmo-Smith <hughns@matrix.org>
Co-authored-by: Michael Telatynski <7t3chguy@gmail.com>
Co-authored-by: Timo <toger5@hotmail.de>

src/sliding-sync-sdk.ts

@@ -612,7 +612,7 @@ export class SlidingSyncSdk {
             timelineEvents = newEvents;
             if (oldEvents.length > 0) {
                 // old events are scrollback, insert them now
-                room.addEventsToTimeline(oldEvents, true, room.getLiveTimeline(), roomData.prev_batch);
+                room.addEventsToTimeline(oldEvents, true, false, room.getLiveTimeline(), roomData.prev_batch);
             }
         }
 
@@ -754,7 +754,7 @@ export class SlidingSyncSdk {
     /**
      * Injects events into a room's model.
      * @param stateEventList - A list of state events. This is the state
-     * at the *START* of the timeline list if it is supplied.
+     * at the *END* of the timeline list if it is supplied.
      * @param timelineEventList - A list of timeline events. Lower index
      * is earlier in time. Higher index is later.
      * @param numLive - the number of events in timelineEventList which just happened,
@@ -763,13 +763,9 @@ export class SlidingSyncSdk {
     public async injectRoomEvents(
         room: Room,
         stateEventList: MatrixEvent[],
-        timelineEventList?: MatrixEvent[],
-        numLive?: number,
+        timelineEventList: MatrixEvent[] = [],
+        numLive: number = 0,
     ): Promise<void> {
-        timelineEventList = timelineEventList || [];
-        stateEventList = stateEventList || [];
-        numLive = numLive || 0;
-
         // If there are no events in the timeline yet, initialise it with
         // the given state events
         const liveTimeline = room.getLiveTimeline();
@@ -820,16 +816,17 @@ export class SlidingSyncSdk {
             timelineEventList = timelineEventList.slice(0, -1 * liveTimelineEvents.length);
         }
 
-        // execute the timeline events. This will continue to diverge the current state
-        // if the timeline has any state events in it.
+        // Execute the timeline events.
         // This also needs to be done before running push rules on the events as they need
         // to be decorated with sender etc.
         await room.addLiveEvents(timelineEventList, {
             fromCache: true,
+            addToState: false,
         });
         if (liveTimelineEvents.length > 0) {
             await room.addLiveEvents(liveTimelineEvents, {
                 fromCache: false,
+                addToState: false,
             });
         }
 
@@ -966,7 +963,7 @@ export class SlidingSyncSdk {
             return a.getTs() - b.getTs();
         });
         this.notifEvents.forEach((event) => {
-            this.client.getNotifTimelineSet()?.addLiveEvent(event);
+            this.client.getNotifTimelineSet()?.addLiveEvent(event, { addToState: false });
         });
         this.notifEvents = [];
     }