I am trying to write a function that can return which arguments from the calling function are missing.
find_missing_args <- function(...) {
args <- rlang::enquos(...)
lapply(args, rlang::is_missing)
}
func <- function(x, y, z) {
find_missing_args(x, y, z)
}
However, the functionality is not as expected:
func(x = 1, y = 2)
Returns
[[1]]
[1] FALSE
[[2]]
[1] FALSE
[[3]]
[1] FALSE
It should return:
[[1]]
[1] FALSE
[[2]]
[1] FALSE
[[3]]
[1] TRUE
Because z was not supplied in the calling function. I would also like to be able to pass which arguments I care about to find_missing_args, so for example:
find_missing_args <- function(...) {
args <- rlang::enquos(...)
lapply(args, rlang::is_missing)
}
func <- function(x, y, z, a, b, c) {
find_missing_args(x, y, z)
}
func(x = 1, y = 2, a = 3, b = 4) will return:
[[1]]
[1] FALSE
[[2]]
[1] FALSE
[[3]]
[1] TRUE
but ignore a, b, c.
UPDATE WITH ANSWER:
find_missing_args <- function(args) {
supplied <- rlang::call_args_names(rlang::caller_call(n = 1))
setdiff(args, supplied)
}
func <- function(x, y, z, a, b, d) {
find_missing_args(c("x","y","z"))
}
func(x = 1, y = 2)
[1] "z"
Interestingly,
find_missing_args <- function(args) {
supplied <- rlang::call_args_names(rlang::caller_call(n = 1))
setdiff(args, supplied)
}
func <- function(x, y, z, a, b, c) {
find_missing_args(c("x","y","z"))
}
func(x = 1, y = 2)
Error in c("x", "y", "z") : argument "c" is missing, with no default
I have not figured out why it interprets c() to be the argument c and not the function c().
I don't delve into these sorts of mechanics often, so I'm not sure how robust or "idiomatic" this is, but I think this gets at what you want?
find_missing_args <- function(...) {
a1 <- rlang::call_args_names(rlang::caller_call(n = 1))
a2 <- rlang::fn_fmls_names(rlang::caller_fn(n = 1))
setdiff(a2,a1)
}
func <- function(x, y, z) {
find_missing_args()
}
func(x = 1,y = 2)