Factorio-Paranoidal_mod/simhelper_1.1.5/modloader.md

modloader is a wrapper to allow running a mostly-unmodified control.lua from a mod as an event_handler library inside level. Examples taken from Nixie Tubes.

Add the following to the top of the mod's main control.lua to prevent double-loading the mod while building saves for simulations:

do
  -- don't load if sim scenario has already loaded this (in another lua state)
  local modloader = remote.interfaces["modloader"]
  if modloader and modloader[script.mod_name] then
    return
  end
end

Also note that if the mod registers any events with filters, the filters will be ignored when loaded by modloader.

Create a scenario with the following in control.lua:

local handler = require("event_handler")
local modloader = require("__simhelper__/modloader.lua")
handler.add_lib(modloader.load("nixie-tubes"))

Create a world from this scenario, open /editor (to remove your character), and save it. Optionally delete all entities and fill with lab tiles. Copy this save into your mod for use in simulations. You can also manually build demo setups if desired.

Define simulation prototypes using this save with commands as needed to set up your desired demo setup. Note that some (all?) of the simulation-specific apis, like create_entities_from_blueprint_string do not raise events, so you may need to manually make your mod code aware of created entities. For example, I trigger Nixie Tubes to rescan the world after spawning simulation entities:

{
    type = "tips-and-tricks-item",
    name = "nixie-tubes",
    tag = "[entity=nixie-tube]",
    category = "nixie-tubes",
    is_title = true,
    order = "zz-00",
    dependencies = {"circuit-network"},
    simulation = {
      save = "__nixie-tubes__/simulations/nixiesim.zip",
      init = [[
        local bp="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"
        game.tick_paused = false
        game.camera_alt_info = true
        local result = {game.surfaces[1].create_entities_from_blueprint_string
        {
          string = bp,
          position = {0, 0},
        }}
        remote.call("nixie-tubes", "RebuildNixies")
      ]],
      update = [[

      ]],
    }
  },

Note that the init and update functions can be defined as regular Lua functions captured using funccapture, see its documentation.