Scripting Error / Module code did not return exactly one value

[WarnFromPlayer (blitz)]

You can write your topic however you want, but you need to answer these questions:

1. What do you want to achieve? The script to work

2. What is the issue? Module code did not return exactly one value

3. What solutions have you tried so far? I’ve rewritten the code multiple times

After that, you should include more details if you have any. Try to make your topic as descriptive as possible, so that it’s easier for people to help you!

Main code with the error

local mob = require(script.Mob)
local map = workspace.Grassland

for i=1, 3 do
	mob.Spawn("Zombie", map)
	task.wait(1)
end

Module

local ServerStorage = game:GetService("ServerStorage")
local mob = {}

function mob.Move(mob, map)
	local humanoid = mob:WaitForChild("Humanoid")
	local waypoints = map.Waypoints

	for waypoint=1, #waypoints:GetChildren() do
		humanoid:MoveTo(waypoints[waypoint].Position)
		humanoid.MoveToFinished:Wait()
	end

end

function mob.Spawn(name, map)
	local mobExists = ServerStorage.Mobs:FindFirstChild(name)

	if mobExists then
		local newMob = mobExists:Clone()
		newMob.HumanoidRootPart.CFrame = map.Start.CFrame
		newMob.Parent = workspace
	else
		warn("Requested mob does not exist:", name)
	end
end

[RealCalculus]

Hi! I believe the issue is that you perhaps forgot to insert a return statement for you function, so when you do mob.Spawn, I suspect it returns no value, since you do not have a return piece. To fix this, at the end of mob.Spawn do the following:

local ServerStorage = game:GetService("ServerStorage")
local mob = {}

function mob.Move(mob, map)
	local humanoid = mob:WaitForChild("Humanoid")
	local waypoints = map.Waypoints

	for waypoint=1, #waypoints:GetChildren() do
		humanoid:MoveTo(waypoints[waypoint].Position)
		humanoid.MoveToFinished:Wait()
	end

end

function mob.Spawn(name, map)
	local mobExists = ServerStorage.Mobs:FindFirstChild(name)

	if mobExists then
		local newMob = mobExists:Clone()
		newMob.HumanoidRootPart.CFrame = map.Start.CFrame
		newMob.Parent = workspace
	else
		warn("Requested mob does not exist:", name)
	end

--return something
       return mobExists -- This is an example of returning exactly one value
end

In a more technical explaination (feel free to ignore this), it expects you to return a Set S whose cardinality is 1, but you return nothing or the empty set, whose cardinality is 0. I hope this helps!