Make sure that callbacks aren't invoked more than once

monarch/utils/async.lua

@@ -0,0 +1,47 @@
+local M = {}
+
+local NOT_STARTED = "not_started"
+local YIELDED = "yielded"
+local RESUMED = "resumed"
+local RUNNING = "running"
+
+function M.async(fn)
+	local co = coroutine.running()
+	
+	local state = NOT_STARTED
+
+	local function await(fn, ...)
+		state = RUNNING
+		fn(...)
+		if state ~= RUNNING then
+			return
+		end
+		state = YIELDED
+		local r = { coroutine.yield() }
+		return unpack(r)
+	end
+
+	local function resume(...)
+		if state ~= RUNNING then
+			state = RUNNING
+			local ok, err = coroutine.resume(co, ...)
+			if not ok then
+				print(err)
+				print(debug.traceback())
+			end
+		end
+	end
+
+	if co then
+		return fn(await, resume)
+	else
+		co = coroutine.create(fn)
+		return resume(await, resume)
+	end
+end
+
+return setmetatable(M, {
+	__call = function(t, ...)
+		return M.async(...)
+	end
+})

monarch/utils/callback_tracker.lua

@@ -6,13 +6,18 @@ function M.create()
 
 	local callback = nil
 	local callback_count = 0
+	local all_callbacks_done = false
 
 	local function is_done()
 		return callback_count == 0
 	end
 
 	local function invoke_if_done()
+		if all_callbacks_done then
+			print("Warning: The same callback will be invoked twice from the callback tracker!", id or "")
+		end
 		if callback_count == 0 and callback then
+			all_callbacks_done = true
 			local ok, err = pcall(callback)
 			if not ok then print(err) end
 		end
@@ -41,20 +46,6 @@ function M.create()
 		invoke_if_done()
 	end
 
-	function instance.yield_until_done()
-		local co = coroutine.running()
-		callback = function()
-			local ok, err = coroutine.resume(co)
-			if not ok then
-				print(err)
-			end
-		end
-		invoke_if_done()
-		if not is_done() then
-			coroutine.yield()
-		end
-	end
-
 	return instance
 end