Unexpected behavior with on.exit(..., add = TRUE) - r

Question

First, please note that the following code creates and removes a folder in the current directory. If it conflicts with any of your file names, don't run this code. I'm not sure how to explain this question without it.
In fun1 I use on.exit(..., add = TRUE) on one line, and on the next I try to remove the directory I created with another on.exit call. It doesn't work.
fun1 <- function(){
if(!file.exists("Rsaber")) dir.create("Rsaber")
on.exit(file.remove(paste0("Rsaber/", list.files("Rsaber"))), add = TRUE)
on.exit(file.remove("Rsaber"))
write.csv("1,2,3,4", file = "Rsaber/new.csv")
}
> fun1()
# Warning message:
# In file.remove("Rsaber") :
# cannot remove file 'Rsaber', reason 'Directory not empty'
> file.exists("Rsaber")
# [1] TRUE
> list.files("Rsaber")
# [1] "new.csv"
However, this method works.
fun2 <- function(){
if(!file.exists("Rsaber")) dir.create("Rsaber")
on.exit(file.remove(c(paste0("Rsaber/", list.files("Rsaber"))), "Rsaber"))
write.csv("1,2,3,4", file = "Rsaber/new.csv")
}
> fun2()
> file.exists("Rsaber")
# [1] FALSE
This second method is also much cleaner and probably the way to go, but
Why doesn't on.exit(..., add = TRUE) behave as expected in fun1 ?
Note that I'm not using a temporary directory here because this is part of a larger function that has a logical argument for determining whether or not to keep a downloaded data file.
System info:
> version[[1]]
# [1] "x86_64-pc-linux-gnu"

Answer 1

I think you need add=TRUE on the second file.remove otherwise the second statement replaces the first:
fun1 <- function(){
if(!file.exists("Rsaber")) dir.create("Rsaber")
on.exit(file.remove(paste0("Rsaber/", list.files("Rsaber"))))
on.exit(file.remove("Rsaber"), add = TRUE)
write.csv("1,2,3,4", file = "Rsaber/new.csv")
}
Also as noted this wont work on windows as the directory will not be considered as a file.
For cross-platform support maybe consider unlink
fun1 <- function(){
if(!file.exists("Rsaber")) dir.create("Rsaber")
on.exit(unlink("Rsaber", recursive = TRUE))
write.csv("1,2,3,4", file = "Rsaber/new.csv")
print(system('ls'))
}