One thing I wish one of the grocery list apps could do was to store recipes, then you choose which recipes you want that day/week/month whenever you go shopping, it's smart enough to know if 3 recipes need flour only put flour on once, then go through and mark ingredients you already have.
Like I can put in a recipe for penne alla vodka or fettuccine alfrado then if I select penne alla vodka it adds : Penne pasta Vodka sauce Heavy cream Mozzarella cheese Parmesan cheese Sausage
Etc to the list. Then I say actually I already have heavy cream and mark it as not needed.
Hmm yeah that's really weird... I can't think of a purpose for a check like that, plus even it was a valid reason throw an exception or return a result indicating failure, don't just corrupt the file