in file prototypes/steam-barrel.lua:3 attempt to index field icons (a nil value)

Oops, somehow managed to make a mistake when zipping it all up and I included an old version of a file.
Should be good now.
Sorry about that and thanks for testing this stuff.
It's really awkward to test both 0.17 and 0.18 because you have to redownload all of Factorio every time you want to switch versions.

Hi!

It's really awkward to test both 0.17 and 0.18 because you have to redownload all of Factorio every time you want to switch versions.

That's not quite true. I've several instances of Factorio installed on my computer: one for 0.17.79 (have some old save games there), one for 0.18 I use for my regular game (this one gets updated whenever a new version of Factorio is released, and contains all of the 100+ mods I play with); one each for testing under 0.17/0.18 (minimal set of mods, usually just some helpers like Creative Mod, eradicator's /sudo an the mod I'm working on at the time + mods I have to check for compatibility).

I downloaded the Factorio versions from factorio.com, and usually just update just one instance online (copying over everything but mod directory, saved games, and blueprints from one installation to the other to save time). Having multiple instances of Factorio installed takes up more diskspace, but as I want to provide updates of my mods for 0.17 and 0.18 as long as 0.17 is the stable version, testing is much easier that way! (Just have to quit the game, change directories, and fire up the other version.)

I'm not sure this is possible if you're playing on Steam, but you should be able to install Factorio locally, and if you can spare some GB of diskspace, it makes testing much easier. :-)

I think it depends on the OS as well. I test both on windows and Mac, on windows I just have a bunch of factorio folders with different build versions (right now there's around 5 of them with different mod constellations for testing). On Mac all user data gets thrown into "~/Library/Application Support/factorio", where I regularly have issues when switching back to an older version. Maybe that's normal, maybe that's just me...