It's a rare thing to find Sri Lankan food in the US, let alone well-prepared Sri Lankan food. Kadupul is excellent on that front and also great for vegans.
This is a small place (large groups will have issues without prior reservations), but clean and modern.
We started off with an order of vegetarian pan rolls (~$8) which were basically Sri Lankan egg rolls, but somewhat different: here they were breaded and had an awesome soft-but-slightly-crunchy texture and were filled with a savory mix of vegetables. The dish comes with three rolls standard.
For my main course I had the "kuttu" (~$13) which is a traditional Sri Lankan dish. It was basically a casserole-type offering made with a coconut sauce, a variety of diced and mashed vegetables, and bits of Sri Lankan bread that reminded me of wide rice-noodles. This dish was delicious: it was savory, spicy, and had a robust flavor that made you want to keep eating. The portion size was huge, too, and easily constituted two meals.
Unfortunately there are no vegan desserts. Our server was aware of what veganism is, and also said that pretty much any dish on the menu could be made vegan (some are made with egg, so make sure to ask questions).
They also have a mockmeat dish somewhere on the menu, but it wasn't clear to me which one that was. The menu could be improved if they labeled their vegan options.
If you haven't had Sri Lankan food before, this serves as a great introduction. I just with they were closer to San Francisco instead of far-off Dublin.