introduce Room.myMembership event

As you don't always have your own member with lazy loading
of members enabled, looking at the sync response section
where a room appears is the most reliable way of determining
the syncing user's membership in a room.

Before we already used this to read the
current room membership with `room.getMyMembership()`,
but we were still using the `RoomMember.membership` event
to detect when the syncing user's membership changed.

This event will help make those checks work well with LL enabled.

src/models/room.js

@@ -178,7 +178,7 @@ function Room(roomId, client, myUserId, opts) {
 
     // read by megolm; boolean value - null indicates "use global value"
     this._blacklistUnverifiedDevices = null;
-    this._syncedMembership = null;
+    this._selfMembership = null;
     this._summaryHeroes = null;
     // awaited by getEncryptionTargetMembers while room members are loading
 
@@ -263,7 +263,7 @@ Room.prototype.getMyMembership = function() {
             return me.membership;
         }
     }
-    return this._syncedMembership;
+    return this._selfMembership;
 };
 
 /**
@@ -278,7 +278,7 @@ Room.prototype.getDMInviter = function() {
             return me.getDMInviter();
         }
     }
-    if (this._syncedMembership === "invite") {
+    if (this._selfMembership === "invite") {
         // fall back to summary information
         const memberCount = this.getInvitedAndJoinedMemberCount();
         if (memberCount == 2 && this._summaryHeroes.length) {
@@ -362,8 +362,15 @@ Room.prototype.getAvatarFallbackMember = function() {
  * Sets the membership this room was received as during sync
  * @param {string} membership join | leave | invite
  */
-Room.prototype.setSyncedMembership = function(membership) {
-    this._syncedMembership = membership;
+Room.prototype.updateMyMembership = function(membership) {
+    const prevMembership = this._selfMembership;
+    this._selfMembership = membership;
+    if (prevMembership !== membership) {
+        if (membership === "leave") {
+            this._cleanupAfterLeaving();
+        }
+        this.emit("Room.myMembership", this, membership, prevMembership);
+    }
 };
 
 Room.prototype._loadMembersFromServer = async function() {
@@ -470,7 +477,7 @@ Room.prototype.clearLoadedMembersIfNeeded = async function() {
  * called when sync receives this room in the leave section
  * to do cleanup after leaving a room. Possibly called multiple times.
  */
-Room.prototype.onLeft = function() {
+Room.prototype._cleanupAfterLeaving = function() {
     this.clearLoadedMembersIfNeeded().catch((err) => {
         console.error(`error after clearing loaded members from ` +
             `room ${this.roomId} after leaving`);

src/sync.js

@@ -123,6 +123,7 @@ SyncApi.prototype.createRoom = function(roomId) {
                           "Room.timelineReset",
                           "Room.localEchoUpdated",
                           "Room.accountData",
+                          "Room.myMembership",
                          ]);
     this._registerStateListeners(room);
     return room;
@@ -976,9 +977,10 @@ SyncApi.prototype._processSyncResponse = async function(
     // Handle invites
     inviteRooms.forEach(function(inviteObj) {
         const room = inviteObj.room;
-        room.setSyncedMembership("invite");
         const stateEvents =
             self._mapSyncEventsFormat(inviteObj.invite_state, room);
+
+        room.updateMyMembership("invite");
         self._processRoomEvents(room, stateEvents);
         if (inviteObj.isBrandNewRoom) {
             room.recalculate();
@@ -993,7 +995,6 @@ SyncApi.prototype._processSyncResponse = async function(
     // Handle joins
     await Promise.mapSeries(joinRooms, async function(joinObj) {
         const room = joinObj.room;
-        room.setSyncedMembership("join");
         const stateEvents = self._mapSyncEventsFormat(joinObj.state, room);
         const timelineEvents = self._mapSyncEventsFormat(joinObj.timeline, room);
         const ephemeralEvents = self._mapSyncEventsFormat(joinObj.ephemeral);
@@ -1009,6 +1010,8 @@ SyncApi.prototype._processSyncResponse = async function(
             );
         }
 
+        room.updateMyMembership("join");
+
         joinObj.timeline = joinObj.timeline || {};
 
         if (joinObj.isBrandNewRoom) {
@@ -1116,8 +1119,6 @@ SyncApi.prototype._processSyncResponse = async function(
     // Handle leaves (e.g. kicked rooms)
     leaveRooms.forEach(function(leaveObj) {
         const room = leaveObj.room;
-        room.setSyncedMembership("leave");
-
         const stateEvents =
             self._mapSyncEventsFormat(leaveObj.state, room);
         const timelineEvents =
@@ -1125,6 +1126,8 @@ SyncApi.prototype._processSyncResponse = async function(
         const accountDataEvents =
             self._mapSyncEventsFormat(leaveObj.account_data);
 
+        room.updateMyMembership("leave");
+
         self._processRoomEvents(room, stateEvents, timelineEvents);
         room.addAccountData(accountDataEvents);
 
@@ -1145,8 +1148,6 @@ SyncApi.prototype._processSyncResponse = async function(
         accountDataEvents.forEach(function(e) {
             client.emit("event", e);
         });
-
-        room.onLeft();
     });
 
     // update the notification timeline, if appropriate.