Hmmm sources, i guess it could just calculate a path without the source position as the last step. So if your creep is right next to the source you get an empty path, if it is 2 fields away it gets a path with one step.. and so on.. 

The main problem i have right now is that when i try to move a creep to an adjacent field with an obstacle on it, moveTo() returns OK but the creep doesn't actually move. So i'm having a hard time finding out if a creeps path is blocked by another (idle) creep. And that is happening because moveTo just checks if the path is not empty. 

 Just noticed this as moveTo returns OK even though the target position is an obstacle: 

suppose you have a single wall at 10,10 surrounded by walkable terrain, then 

new RoomPosition(9,10,'sim').findPathTo(10,10)

will return

[{"x":10,"y":10,"dx":1,"dy":0,"direction":3}]

instead of an empty path as i would expect.