I have a trickle charger cable on my motorcycle battery and in the dark I mistakenly put both charger cable leads on the positive battery terminal, what happened to the battery by trickle charging with both positive and negative on the same battery terminal?
Nothing happened to the battery.
If your trickle charger doesn't have short circuit protection, it may be destroyed now. However, the battery is unaffected.
Try to test if your charger works by charging with it normally, by putting positive to positive and negative to negative.