ComfyFactorio/modules/market_friendly_fire_protection.lua

local Event = require 'utils.event'

local function on_entity_damaged(event)
    if event.entity.name ~= 'market' then
        return false
    end
    if event.cause then
        if event.cause.force.name == 'enemy' then
            return false
        end
    end
    event.entity.health = event.entity.health + event.final_damage_amount
    return true
end

Event.add(defines.events.on_entity_damaged, on_entity_damaged)