I am working on a wrapper function for ggplot that looks somewhat like this

plot_wrapper <- function(df, group_by, color_by=NULL) {
  ggplot(df, aes(x=.data[[groupby]], y=value) + 
    geom_quasirandom()
}

Now I would like to conditionally pass color_by to geom_quasirandom(aes(color=.data[[color_by]])) if color_by is not NULL. How can I do that without duplicating code and without using the deprecated aes_string?

I tried

color_args = ifelse(is.null(color_by), list(), list(color=.data[[groupby]]))
ggplot(df, aes(x=.data[[groupby]], y=value) + 
    geom_quasirandom(aes(!!!color_args)

but it fails with

Error in `geom_quasirandom()`:
! Problem while computing aesthetics.
ℹ Error occurred in the 2nd layer.
Caused by error:
! object '.data[[color_by]]' not found

Similarly

geom_quasirandom(aes(color = !!ifelse(is.null(color_by), NULL, .data[[color_by]])))

fails with

Error in `plot_comparison()`:
! Can't subset `.data` outside of a data mask context.
Run `rlang::last_trace()` to see where the error occurred.

I suspect it requires the right combination of quoting and unquoting but I haven’t found it yet.