clear out of band members in store when leaving room

src/models/room.js

@@ -457,6 +457,29 @@ Room.prototype.loadMembersIfNeeded = function() {
     return this._membersPromise;
 };
 
+/**
+ * Removes the lazily loaded members from storage if needed
+ */
+Room.prototype.clearLoadedMembersIfNeeded = async function() {
+    if (this._opts.lazyLoadMembers && this._membersPromise) {
+        await this.loadMembersIfNeeded();
+        this._membersPromise = null;
+        await this._client.store.clearOutOfBandMembers(this.roomId);
+    }
+};
+
+/**
+ * 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() {
+    this.clearLoadedMembersIfNeeded().catch((err) => {
+        console.error(`error after clearing loaded members from ` +
+            `room ${this.roomId} after leaving`);
+        console.dir(err);
+    });
+};
+
 /**
  * Reset the live timeline of all timelineSets, and start new ones.
  *

src/store/stub.js

@@ -272,6 +272,10 @@ StubStore.prototype = {
     setOutOfBandMembers: function() {
         return Promise.resolve();
     },
+
+    clearOutOfBandMembers: function() {
+        return Promise.resolve();
+    },
 };
 
 /** Stub Store class. */

src/sync.js

@@ -1106,6 +1106,7 @@ SyncApi.prototype._processSyncResponse = async function(
     leaveRooms.forEach(function(leaveObj) {
         const room = leaveObj.room;
         room.setSyncedMembership("leave");
+        room.onLeft();
 
         const stateEvents =
             self._mapSyncEventsFormat(leaveObj.state, room);