Why have the design-pattern `function()` with the body `function_impl()`, defined elsewhere?

[jdhoffa]

For example, in the file scale_colour_r2dii.R, there is a function defined as r2dii_pal, that has an abort call and a body of r2dii_pal_impl that is defined in a different file utils.R.

What are the pros to doing this?

The main cons I notice are that context shifting (and not being able to directly see what a function does when looking at it) takes time and makes it difficult to interpret what a function does.

[jdhoffa]

I think the last place this appears is here:

r2dii.plot/R/utils.R

Lines 282 to 291 in ec42cf3

	r2dii_pal_impl <- function(x, data, column) {
	x <- x %||% data[[column]]
	values <- as_tibble_col(x, column) %>%
	inner_join(data, by = column) %>%
	pull(.data$hex)
	max_n <- length(values)
	f <- manual_pal(values)
	attr(f, "max_n") <- max_n
	f
	}

[MonikaFu]

This implementation was done to DRY the code but indeed I agree that it could probably do without both r2dii_pal() and r2dii_pal_impl() and just one helper function after some refactoring.