Revdep: S3 generic/method consistency

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Problem

This issue emerged from a reverse dependency check 9f80c8c.

We have updated some S3 generics like ggplot_build(), ggplot_add() and added ... as an argument. This allows for future expansion and is generally considered better practise than having a fixed set of arguments in a generic.

Ideally, methods follow the generic but having improved the generic, packages that have methods for this generic may now encounter the following warning:

checking S3 generic/method consistency ... WARNING
``
ggplot_build:
  function(plot, ...)
ggplot_build.<custom_class>:
  function(plot)
See section ‘Generic functions and methods’ in the ‘Writing R
Extensions’ manual.
``

The relevant part from the manual mentioned in the message is this:

A method must have all the arguments of the generic, including … if the generic does.

Solution

The solution would be to just include ... even if this is not used in the method. For example:

#' @export
ggplot_build.my_class <- function(plot, ...) {
  <your code>
}

For ggplot_add(), it depends whether you use the object_name argument or not.
If you do, you can use the following as template:

#' @export
ggplot_add.my_class <- function(object, plot, object_name, ...) {
  <your code>
}

And if you do not use the object_name argument, you can use:

#' @export
ggplot_add.my_class <- function(object, plot, ...) {
  <your code>
}

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