when enabling LL, set the flag on Filter, rather than doing /filter

src/filter.js

@@ -56,13 +56,6 @@ Filter.LAZY_LOADING_MESSAGES_FILTER = {
     lazy_load_members: true,
 };
 
-Filter.LAZY_LOADING_SYNC_FILTER = {
-    room: {
-        state: Filter.LAZY_LOADING_MESSAGES_FILTER,
-    },
-};
-
-
 /**
  * Get the ID of this filter on your homeserver (if known)
  * @return {?Number} The filter ID
@@ -96,6 +89,7 @@ Filter.prototype.setDefinition = function(definition) {
     //     "state": {
     //       "types": ["m.room.*"],
     //       "not_rooms": ["!726s6s6q:example.com"],
+    //       "lazy_load_members": true,
     //     },
     //     "timeline": {
     //       "limit": 10,
@@ -177,6 +171,10 @@ Filter.prototype.setTimelineLimit = function(limit) {
     setProp(this.definition, "room.timeline.limit", limit);
 };
 
+Filter.prototype.setLazyLoadMembers = function(enabled) {
+    setProp(this.definition, "room.state.lazy_load_members", !!enabled);
+};
+
 /**
  * Control whether left rooms should be included in responses.
  * @param {boolean} includeLeave True to make rooms the user has left appear

src/sync.js

@@ -511,6 +511,12 @@ SyncApi.prototype.sync = function() {
         checkLazyLoadStatus(); // advance to the next stage
     }
 
+    function createDefaultFilter() {
+        const filter = new Filter(client.credentials.userId);
+        filter.setTimelineLimit(self.opts.initialSyncLimit);
+        return filter;
+    }
+
     const checkLazyLoadStatus = async () => {
         debuglog("Checking lazy load status...");
         if (this.opts.lazyLoadMembers && client.isGuest()) {
@@ -520,19 +526,11 @@ SyncApi.prototype.sync = function() {
             debuglog("Checking server lazy load support...");
             const supported = await client.doesServerSupportLazyLoading();
             if (supported) {
-                try {
-                    debuglog("Creating and storing lazy load sync filter...");
-                    this.opts.filter = await client.createFilter(
-                        Filter.LAZY_LOADING_SYNC_FILTER,
-                    );
-                    debuglog("Created and stored lazy load sync filter");
-                } catch (err) {
-                    logger.error(
-                        "Creating and storing lazy load sync filter failed",
-                        err,
-                    );
-                    throw err;
+                debuglog("Enabling lazy load on sync filter...");
+                if (!this.opts.filter) {
+                    this.opts.filter = createDefaultFilter();
                 }
+                this.opts.filter.setLazyLoadMembers(true);
             } else {
                 debuglog("LL: lazy loading requested but not supported " +
                     "by server, so disabling");
@@ -575,8 +573,7 @@ SyncApi.prototype.sync = function() {
         if (self.opts.filter) {
             filter = self.opts.filter;
         } else {
-            filter = new Filter(client.credentials.userId);
-            filter.setTimelineLimit(self.opts.initialSyncLimit);
+            filter = createDefaultFilter();
         }
 
         let filterId;