Assert that at most one of several arguments is supplied — assert_mutually_exclusive • assert

Treats a NULL argument as "not supplied". Raises an error if two or more of the arguments in ... are non-NULL. Supplying none is allowed.

Usage

assert_mutually_exclusive(..., 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

draw <- function(colour = NULL, palette = NULL) {
  assert_mutually_exclusive(colour, palette)
  "ok"
}
draw(colour = "red")
#> [1] "ok"