Signal deprecated argument by using self-documenting sentinel deprecated() as default argument. Test whether the caller has supplied the argument with is_present().

deprecated()

is_present(arg)

## Arguments

arg A deprecated() function argument.

## Magical defaults

We recommend importing lifecycle::deprecated() in your namespace and use it without the namespace qualifier.

In general, we advise against such magical defaults, i.e. defaults that cannot be evaluated by the user. In the case of deprecated(), the trade-off is worth it because the meaning of this default is obvious and there is no reason for the user to call deprecated() themselves.

## Examples

foobar_adder <- function(foo, bar, baz = deprecated()) {
# Check if user has supplied baz instead of bar
if (lifecycle::is_present(baz)) {

# Signal the deprecation to the user
foobar_adder(1, 2)#> [1] 3foobar_adder(1, baz = 2)#> Warning: The baz argument of bar_adder() is deprecated as of foo 1.0.0.
#> Please use the bar argument instead.
#> Call lifecycle::last_warnings() to see where this warning was generated.#> [1] 3