Make uncount() generic (#1358)

* Make `uncount()` generic

* Document dots for `uncount()`

* NEWS bullet

* Move `check_dots_used()` into `uncount()` generic.

NAMESPACE

@@ -32,6 +32,7 @@ S3method(separate_rows,data.frame)
 S3method(separate_rows_,data.frame)
 S3method(spread,data.frame)
 S3method(spread_,data.frame)
+S3method(uncount,data.frame)
 S3method(unite,data.frame)
 S3method(unite_,data.frame)
 S3method(unnest,data.frame)

NEWS.md

@@ -1,5 +1,11 @@
 # tidyr (development version)
 
+* `uncount()` is now generic so implementations can be provided for objects
+  other than data frames (@mgirlich, #1358).
+
+* `uncount()` gained the `...` argument. It comes between the required and the
+  optional arguments (@mgirlich, #1358).
+
 * `pivot_longer()` gained a new `cols_vary` argument for controlling the
   ordering of the output rows relative to their original row number (#1312).
 

R/uncount.R

@@ -6,6 +6,7 @@
 #' @param data A data frame, tibble, or grouped tibble.
 #' @param weights A vector of weights. Evaluated in the context of `data`;
 #'   supports quasiquotation.
+#' @param ... Additional arguments passed on to methods.
 #' @param .id Supply a string to create a new variable which gives a unique
 #'   identifier for each created row.
 #' @param .remove If `TRUE`, and `weights` is the name of a column in `data`,
@@ -21,7 +22,13 @@
 #'
 #' # Or expressions
 #' uncount(df, 2 / n)
-uncount <- function(data, weights, .remove = TRUE, .id = NULL) {
+uncount <- function(data, weights, ..., .remove = TRUE, .id = NULL) {
+  check_dots_used()
+  UseMethod("uncount")
+}
+
+#' @export
+uncount.data.frame <- function(data, weights, ..., .remove = TRUE, .id = NULL) {
   weights_quo <- enquo(weights)
   w <- dplyr::pull(dplyr::mutate(data, `_weight` = !!weights_quo))
   # NOTE `vec_cast()` and check for positive weights can be removed