so I am trying to add a list of items to a list, there’s 1 item that I would like to either add (or not add) according to some flag

list.addAll(listOfNotNull(item1, item2, if (flag) item3 else null))

But don’t do that.

There are several options, but it depends on the bigger picture. You said you wanted to add a list of items. Is it an actual

List

? Because in the snippet you showed it seems you have several variables but not a list to add. Also, why are you using a mutable list in the first place here? Are you interacting with the mutable list long term? Or is it a temporary object that is then just used as a

List

? If the latter,

buildList { ... }

would likely be more appropriate.

In fact you could even use

takeIf

list.addAll(listOfNotNull(..., item3.takeIf { flag }))

But probably the recommended, and cheaper way to do this is with `buildList`:

buildList(3) { // 3 is the maximum size of things you're going to add
  add(item1)
  add(item2)
  if(flag) add(item3)
}

nice!