By holding back that kind of information, one is being more than fair to the smoker but not to the other party.
Just equal the scales and tell it like it is, that the person smokes but promises to quit. In this way you are being fair to the other person and honest, but not unfair, to the smoker.
Smoking and promising to quit is not the same status as being a non-smoker, and it should not be pretended to be so or to be thought of in that light.
Speaking of light, anyone have a cigarette? lol Just kidding. I do not smoke.
Good luck, and I hope they quit smoking.