I'm really sorry if this has already been fixed but I couldn't find it mentioned so here we go.
- Place ghost.
- Bot picks up item from chest.
- Use the upgrade planner on ghost (before the bot gets there).
- Bot slaps down upgraded item (magically transforming whatever the bot was holding ie you never have to make blue belts or T3 assemblers).
- Notify a bot if it's target ghost is upgraded (like happens when the ghost is deleted).
- Alternatively, have the bot check at the last moment if the item it is placing down is correct (then fetching a correct one if required).
Reproduced each time.
Sandbox, rail world, all technologies unlocked.
No upgraded items existed outside of my inventory, only the base items inside a storage chest (yellow belt, yellow underground belt, yellow splitter, assembler, fast inserter, stone furnace).
I was able to magically upgrade the following,
- yellow belt -> red belt
- red belt -> blue belt
- yellow belt -> blue belt (if you upgrade the yellow belt ghost twice before the bot gets there)
^^^ same with splitters, underground belts and assemblers.
- fast inserter -> stack inserter
- stone furnace -> steel furnace
I was playing on railworld and at the stage where I had some blueprints with red belts and fast inserters that I hadn't yet been bothered enough to have made with blue belts and stack inserters, so I just slapped down one of my outdated blueprints with the intention of upgrading the parts then remaking the blueprints and noticed a bunch of bots already moving toward my newly created ghosts and I was all like "Oh well, guess they'll just have to take 'em all back and get the right item..."
I then used the upgrade planner on the ghosts and the ghosts upgraded to blue belts and stack inserters, as you would expect. Much to my surprise however, the bots continued on toward the ghosts with their red belts and fast inserters. I figured it may be down to some kind of CPU saving trick where the bots ignore changes to the world until they get to where they're going. Once the bots arrived at their respective target ghosts however, they slapped down blue belts and stack inserters (instead of the red belts and fast inserters they were carrying).
At this point, I opened up a sandbox world to test it out a little. Turns out it even works on double upgrades.
It isn't a really game-breaking bug, but it shouldn't happen and it's easy to fix, or at least easier to fix than fluids mixing unintentionally...