Assert that exactly one of several arguments is supplied — assert_exactly_one • assert

Treats a NULL argument as "not supplied". Raises an error unless exactly one argument in ... is non-NULL.

Usage

assert_exactly_one(..., call = rlang::caller_env())

Arguments

...: Two or more arguments to check, typically optional parameters of the calling function that default to NULL.
call: Environment used as the error's call context. Defaults to the calling function, so errors point at the user's code.

Value

NULL, invisibly.

Examples

connect <- function(url = NULL, socket = NULL) {
  assert_exactly_one(url, socket)
  "ok"
}
connect(url = "localhost")
#> [1] "ok"