Modify tbl_df subclass print in a package

[urswilke]

Not sure if this topic belongs here and rather a comment than an issue. I was struggling to have a customized print of a tibble subclass "my_subclass" in a package using pillar.

If I understand correctly, the solution was to add these roxygen2 comments (and then devtools::document()):

#' @importFrom
#' @export

for instance

#' @importFrom pillar tbl_sum
#' @export
tbl_sum.my_subclass <- function(x, ...) {
  c("custom_title_string")
}

I was just wondering if it might be worth to add such a comment to the docs, because I lost too much time with this. For further explanation you can also check out this dummy package that I made to test this and which helped me to find the solution (the R6 part there isn't relevant for this topic I think).

[krlmlr]

Good point. Are you suggesting tweaking https://pillar.r-lib.org/articles/extending.html, or other texts?

[urswilke]

Yes I think that would be the best place. It was the article I read most when learning this.

[moodymudskipper]

To create in a package a custom S3 method for a tibble subclass we need to import the generic, and export the method. This is not specific to pillar but is a detail that is easy to overlook and can confuse users.

We wish to improve 'vignettes/extending.Rmd' to avoid this confusion.