I was trying out a new map, planning on combining FactorioExtended + Rampant when I got this error:
Error while running setup for entity prototype "pylon-target-rampant" (radar): Entity must produce no item result result or mine to an item that isn't hidden when next_upgrade is set.
To reproduce the error
Factorio 0.17.79
Mods installed
Rampant 0.17.31
FactorioExtended-Plus-Core 0.2.0
FactorioExtended-Plus-Machines 0.2.4
Mod setting that causes the problem to occur:
World: Enable new enemies (enabled)
After making setting change restart factorio and the game will no longer load.
Looks like the "FactorioExended Plus" mod wanted to make radar's upgradable and changed the vanila object
data.raw["radar"]["radar"].next_upgrade = "radar-mk2"
Your 'pylon-target-rampant' is a clone of the vanila radar, but doesnt get added until the "data-final-fixes" stage after "FactorioExended Plus" has changed the base entity.
I made a fix to my local copy of Rampant, by adding this line to EnergyThief.lua
chest.next_upgrade = nil
I have also made a pull request to get this added to your mod.
https://github.com/veden/Rampant/pull/24