iserith
Magic Wordsmith
The way I rule it is that, if you have a fight during a long rest, that's fine - as long as you don't have to retreat from your camp. If you need to quit your camp, that's effectively the hour-long interruption and you have to start the rest again once you get resettled. It doesn't happen often, but it does happen sometimes, largely depending on the condition of the PCs when they rest and how nasty the monster(s) that was indicated by the random encounter check. That strikes me as the right balance and is easy for the players to understand and plan around.