Upvote:5
You will have to go through the Swiss part of the airport and the Swiss rules on customs, immigration and Covid-related restrictions all apply in principle. You cannot assume that only the French rules apply. In fact, you could probably ignore the French rules (not that I would advise it) whereas the airline and border police will enforce whatever restrictions the Swiss authorities have put in place.
In practice, Ireland is not currently on the high-risk country list from the Swiss Federal Department of Justice and Police and transit should be possible but that would be by virtue of Swiss rules not because traveling to France would allow you to ignore them.