thisisnic commented on code in PR #13786:
URL: https://github.com/apache/arrow/pull/13786#discussion_r945796704
##########
r/R/dplyr-mutate.R:
##########
@@ -151,3 +153,95 @@ ensure_named_exprs <- function(exprs) {
names(exprs)[unnamed] <- map_chr(exprs[unnamed], format_expr)
exprs
}
+
+# Take the input quos and unfold any instances of across()
+# into individual quosures
+unfold_across <- function(.data, quos_in) {
+ quos_out <- list()
+ # Check for any expressions starting with across
+ for (quo_i in seq_along(quos_in)) {
+ quo_in <- quos_in[quo_i]
+ quo_expr <- quo_get_expr(quo_in[[1]])
+ quo_env <- quo_get_env(quo_in[[1]])
+
+ if (is_call(quo_expr, "across")) {
+ new_quos <- list()
+ across_call <- call_match(quo_expr, dplyr::across, defaults = TRUE)
+
+ if (!all(names(across_call[-1]) %in% c(".cols", ".fns", ".names"))) {
+ abort("`...` argument to `across()` is deprecated in dplyr and not
supported in Arrow")
+ }
+
+ # ARROW-17364: add support for .names argument
+ if (!is.null(across_call[[".names"]])) {
+ abort("`.names` argument to `across()` not yet supported in Arrow")
+ }
+
+ # use select() to get the columns so we can take advantage of tidyselect
+ source_cols <- names(dplyr::select(.data, !!across_call[[".cols"]]))
+ funcs <- across_call[[".fns"]]
+
+ # calling across() with .fns = NULL returns all columns unchanged
+ if (is_empty(funcs)) {
+ return()
+ }
+
+ if (!is_list(funcs) && as.character(funcs)[[1]] == "~") {
+ abort(
+ paste(
+ "purrr-style lambda functions as `.fns` argument to `across()`",
Review Comment:
Yep, if I try to do that, I get the error:
```
Error in as_mapper(funcs) :
Formula must carry an environment.
```
Currently trying to work out how to fix that, `f_env()` looks promising!
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