Fix Adding systems and items to the world inside a call to system:onAdd()

tiny.lua

@@ -348,7 +348,7 @@ local worldMetaTable
 -- Can optionally add default Systems and Entities. Returns the new World along
 -- with default Entities and Systems.
 function tiny.world(...)
-    local ret = {
+    local ret = setmetatable({
 
         -- List of Entities to add
         entitiesToAdd = {},
@@ -370,13 +370,13 @@ function tiny.world(...)
 
         -- List of Systems
         systems = {}
-    }
+    }, worldMetaTable)
 
     tiny_add(ret, ...)
     tiny_manageSystems(ret)
     tiny_manageEntities(ret)
 
-    return setmetatable(ret, worldMetaTable), ...
+    return ret, ...
 end
 
 --- Adds an Entity to the world.
@@ -461,6 +461,9 @@ function tiny_manageSystems(world)
         return
     end
 
+    world.systemsToAdd = {}
+    world.systemsToRemove = {}
+
     local entities = world.entities
     local systems = world.systems
     local system, index, filter
@@ -531,6 +534,7 @@ end
 
 -- Adds and removes Entities that have been marked.
 function tiny_manageEntities(world)
+
     local e2a, e2r = world.entitiesToAdd, world.entitiesToRemove
 
     -- Early exit
@@ -538,6 +542,9 @@ function tiny_manageEntities(world)
         return
     end
 
+    world.entitiesToAdd = {}
+    world.entitiesToRemove = {}
+
     local entities = world.entities
     local systems = world.systems
     local entityCount = world.entityCount
@@ -696,9 +703,7 @@ end
 
 --- Sets the index of a System in the World, and returns the old index. Changes
 -- the order in which they Systems processed, because lower indexed Systems are
--- processed first. If 'index' < 0, then sets 'index' relative to the last index
+-- processed first. Returns the old system.index.
--- in the World; -1 is the index of the last System, -2 is the second to last,
--- and so on. Returns the old system.index.
 function tiny.setSystemIndex(world, system, index)
     local oldIndex = system.index
     local systems = world.systems
@@ -734,7 +739,10 @@ worldMetaTable = {
         getSystemCount = tiny.getSystemCount,
         getSystemIndex = tiny.getSystemIndex,
         setSystemIndex = tiny.setSystemIndex
-    }
+    },
+    __tostring = function(self)
+        return "tiny-ecs_World"
+    end
 }
 
 return tiny