At the end of #19733166, I donated, trashing 5 hunting grounds, and gaining all the estates and a few dutchies.
That left 3 empty piles. But the game didn't end.
Is this a bug, or does the game not end if you end piles between turns?
It's correct
The end of game conditions are only checked when a turn has ended. Not at other times (either in or outside of turns).
Interesting... so, if you want to do a donate/hunting grounds end, you'd better be sure your opponent can't come back next turn (or return a card (encampment or ambassador).
Live and learn.