respond to CR

// FREEBIE

SignalServiceKit/src/Messages/DeviceSyncing/OWSSyncGroupsMessage.m

@@ -49,14 +49,16 @@ NS_ASSUME_NONNULL_BEGIN
     [dataOutputStream open];
     OWSGroupsOutputStream *groupsOutputStream = [OWSGroupsOutputStream streamWithOutputStream:dataOutputStream];
 
-    [TSGroupThread enumerateCollectionObjectsUsingBlock:^(id obj, BOOL *stop) {
+    [TSGroupThread
-        if (![obj isKindOfClass:[TSGroupThread class]]) {
+        enumerateCollectionObjectsWithTransaction:transaction
-            DDLogVerbose(@"Ignoring non group thread in thread collection: %@", obj);
+                                       usingBlock:^(id obj, BOOL *stop) {
-            return;
+                                           if (![obj isKindOfClass:[TSGroupThread class]]) {
-        }
+                                               DDLogVerbose(@"Ignoring non group thread in thread collection: %@", obj);
-        TSGroupModel *group = ((TSGroupThread *)obj).groupModel;
+                                               return;
-        [groupsOutputStream writeGroup:group];
+                                           }
-    }];
+                                           TSGroupModel *group = ((TSGroupThread *)obj).groupModel;
+                                           [groupsOutputStream writeGroup:group];
+                                       }];
 
     [groupsOutputStream flush];
     [dataOutputStream close];

SignalServiceKit/src/Storage/TSYapDatabaseObject.h

@@ -81,9 +81,20 @@
 + (instancetype)fetchObjectWithUniqueID:(NSString *)uniqueID NS_SWIFT_NAME(fetch(uniqueId:));
 
 /**
- *  Saves the object with shared readWrite connection.
+ * Saves the object with the shared readWrite connection.
+ *
+ * This method will block if another readWrite transaction is open.
  */
 - (void)save;
+
+/**
+ * Saves the object with the shared readWrite connection - does not block.
+ *
+ * Be mindful that this method may clobber other changes persisted
+ * while waiting to open the readWrite transaction.
+ *
+ * @param completionBlock is called on the main thread
+ */
 - (void)saveAsyncWithCompletionBlock:(void (^_Nullable)(void))completionBlock;
 
 /**