[16.20] Potential exploits crafting with damaged items

[Silari]

Haven't seen this posted anywhere and search didn't find anything. Definitely been around since 0.15, probably earlier.

1) Have a partially used firearm magazine
2) use it to craft a piercing magazine, but cancel the crafting before completion
3) A fully repaired firearm magazine is returned

This includes any partially used ammo and damaged items, like walls/assemblers/etc. Any item that is used in a crafting recipe can be repaired this way for no cost. Uranium ammo can't, but piercing ammo can.

One would expect to get the original, partially used magazine back. Instead, a fully loaded/repaired item is always returned. Alternatively, one would expect that damaged items not be allowed to use for crafting. Ideally, allowing damaged items for crafting on a per-recipe basis (pretty sure modded Minecraft has a mechanism for this, for similar reasons). No idea how feasible any fix is with Factorio's current system, but gotta report it at least.

The usage in vanilla factorio is only a minor exploit, though it could be an issue in PvP games if one team abuses this for free ammo. I don't see any way to automate this in vanilla, so it would always need to be by hand which limits it. Since you're not getting a lot each time (9 iron+5 copper each p. magazine, or a repair pack for a building), it comes out as not anything major.

In modded games, it can be more serious. As an example, Bob's Modules allows researching modules using the same components used to build modules. Using this exploit means never spending ANY materials to complete research, as you can craft-cancel them to full durability every time by craft-canceling a module they're used in. With a mod that allows setting assembler recipes this could even be fully automated fairly easily. Circuit timer triggers to remove item before it"s fully consumed, gets put in assembler, crafting starts, recipe is reset, items are returned fully repaired, item returned to lab, circuit timer resets and it starts over.


Related, some people might consider using a 1/10 magazine for crafting and getting a 10/10 magazine back to also be an issue, but that's very minor comparatively.

[Rseding91]

Thanks for the report. Unfortunately there's no way to work around this issue that wouldn't add a massive amount of complexity to the crafting system which I don't want to do in the middle of bug fixing. For now I'm going to move this to minor issues.

We may or may not change this in the future but for now that's just how it works. If the mod(s) want to prevent the issue they need to not use those kinds of things for both crafting and research.