from retail

WeakAuras/SubscribableObject.lua

@@ -8,6 +8,7 @@ local SubscribableObject =
 {
   ClearSubscribers = function(self)
     self.events = {}
+    self.subscribers = {}
   end,
 
   ClearCallbacks = function(self)
@@ -21,6 +22,12 @@ local SubscribableObject =
     end
 
     self.events[event] = self.events[event] or {}
+    self.subscribers[event] = self.subscribers[event] or {}
+    if self.subscribers[event][subscriber] then
+      -- Already subscribed, just return
+      return
+    end
+    self.subscribers[event][subscriber] = true
     local pos = highPriority and 1 or (#self.events[event] + 1)
     if TableHasAnyEntries(self.events[event]) then
       tinsert(self.events[event], pos, subscriber)
@@ -34,6 +41,12 @@ local SubscribableObject =
 
   RemoveSubscriber = function(self, event, subscriber)
     if self.events[event] then
+      if not self.subscribers[event][subscriber] then
+        -- Not subscribed
+        return
+      end
+
+      self.subscribers[event][subscriber] = nil
       local index = tIndexOf(self.events[event], subscriber)
       if index then
         tremove(self.events[event], index)
@@ -68,6 +81,7 @@ function Private.CreateSubscribableObject()
   for f, func in pairs(SubscribableObject) do
     system[f] = func
     system.events = {}
+    system.subscribers = {}
     system.callbacks = {}
   end
   return system