[GitHub] [arrow] paleolimbot commented on a change in pull request #12179: ARROW-14609 [R] left_join by argument error message mismatch

[GitBox <gi...@apache.org>]

paleolimbot commented on a change in pull request #12179:
URL: https://github.com/apache/arrow/pull/12179#discussion_r787927677



##########
File path: r/R/dplyr-join.R
##########
@@ -117,10 +117,30 @@ handle_join_by <- function(by, x, y) {
   if (is.null(names(by))) {
     by <- set_names(by)
   }
-  # TODO: nicer messages?
-  stopifnot(
-    all(names(by) %in% names(x)),
-    all(by %in% names(y))
-  )
+
+  missing_x_cols <- setdiff(names(by), names(x))
+  missing_y_cols <- setdiff(by, names(y))
+  message_x <- NULL
+  message_y <- NULL
+
+  if (length(missing_x_cols) > 0) {
+    message_x <- paste(
+      oxford_paste(missing_x_cols, quote_symbol = "`"),
+      "not present in x."
+      )

Review comment:
       ```suggestion
       )
   ```




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