[0.7.56] can not listen to creation events for space elevators

[hgschmie]

I have a mod that has an interest to know when a space elevator is created. So I set up code that listens to the creation events (defines.events.on_built_entity, defines.events.on_robot_built_entity, defines.events.on_space_platform_built_entity, defines.events.script_raised_built, defines.events.script_raised_revive) for se-space-elevator entities.

Now, my mod does not receive these events all the time. To be exact, the event is only received in two of the four possible orientations of a space elevator (as a assembling machine, it has four possible orientations and you can rotate through those).

This was surprising until I realized that the current code does this during the "on_entity_created" handler:

if direction ~= entity.direction then
    local old_entity = entity
    entity = surface.create_entity{
      name = SpaceElevator.name_space_elevator,
      position = position,
      direction = direction,
      force = force
    }
    ---@cast entity -?
    old_entity.destroy()
end

As the created entity is discarded within the handler, Factorio does not call other handlers (the entity that it would call about has been invalidated).

Now, this would be a minor annoyance if the create_entity call would have raise_built = true. In that case, my mod would receive that event for the new entity that was created within that handler.

This fixes the problem:

diff --git i/scripts/space-elevator.lua w/scripts/space-elevator.lua
index 93de605..4d9f8cf 100644
--- i/scripts/space-elevator.lua
+++ w/scripts/space-elevator.lua
@@ -464,10 +464,12 @@ function SpaceElevator.on_entity_created(event)
       name = SpaceElevator.name_space_elevator,
       position = position,
       direction = direction,
+      raise_built = true,
       force = force
     }
     ---@cast entity -?
     old_entity.destroy()
+    return
   end

   -- returns nil on failed create

Note that you MUST add the return, otherwise you win https://forums.factorio.com/viewtopic.php?t=133665

[BurninSun]

This is fixed for next release.
Just be aware that if your mod is loaded before SE, you will get two events. Once for the original built call which we will then destroy, and the second time for the script built version. If your mod loads after, you will only get the script built event.
I don't raise events for the matching opposite side as it would cause a nightmare of recursive calls.