- Refactored to remove unnecessary addUsernameByIdAndMute method

- Completed setReadOnlyById to set/unset muted user array

packages/rocketchat-channel-settings/server/models/Rooms.coffee

@@ -16,10 +16,21 @@ RocketChat.models.Rooms.setReadOnlyById = (_id, readOnly) ->
 		$set:
 			ro: readOnly
 
+	update.$set.muted = []
+
 	if readOnly
-		users = @findOne(query, { fields: { usernames: 1 }})?.usernames
-	else
-		update.$set.muted = []
+		# we want to mute all users without the post-read-only permission
+
+		# get all usernames for this room
+		users = @findOne(query, { fields: { usernames: 1 }})
+
+		users.usernames.forEach (userName) ->
+
+			# lookup the user
+			user = RocketChat.models.Users.findOneByUsername userName
+
+			if user != null and RocketChat.authz.hasPermission(user._id, 'post-read-only') is false
+				update.$set.muted.push userName
 
 	return @update query, update
 

server/methods/joinRoom.coffee

@@ -23,10 +23,10 @@ Meteor.methods
 		RocketChat.callbacks.run 'beforeJoinRoom', user, room
 
 		# Automatically mute users in read only rooms
-		if room.ro and not RocketChat.authz.hasPermission(Meteor.userId(), 'post-read-only')
-			RocketChat.models.Rooms.addUsernameByIdAndMute rid, user.username
-		else
-			RocketChat.models.Rooms.addUsernameById rid, user.username
+		
+		muted = room.ro and not RocketChat.authz.hasPermission(Meteor.userId(), 'post-read-only')
+
+		RocketChat.models.Rooms.addUsernameById rid, user.username, muted
 
 		RocketChat.models.Subscriptions.createWithRoomAndUser room, user,
 			ts: now