Signal deprecated argument by using self-documenting sentinel
deprecated() as default argument. Test whether the caller has
supplied the argument with is_present().
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
deprecate_warn("1.0.0", "foo::bar_adder(baz = )", "foo::bar_adder(bar = )")
# Deal with the deprecated argument for compatibility
bar <- baz
}
foo + bar
}
foobar_adder(1, 2)
#> [1] 3
foobar_adder(1, baz = 2)
#> Warning: The `baz` argument of `bar_adder()` is deprecated as of foo 1.0.0.
#> ℹ Please use the `bar` argument instead.
#> [1] 3