[GitHub] [arrow] nealrichardson commented on a diff in pull request #13690: ARROW-17088: [R] Use `.arrow` as extension of IPC files of datasets

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

nealrichardson commented on code in PR #13690:
URL: https://github.com/apache/arrow/pull/13690#discussion_r930110815


##########
r/tests/testthat/test-dataset-write.R:
##########
@@ -139,6 +139,23 @@ test_that("Writing a dataset: Parquet->Parquet (default)", {
   )
 })
 
+test_that("Writing a dataset: `basename_template` default behavier", {

Review Comment:
   We should have a test of providing `basename_template`, looks like we don't have one. Would you be interested in adding one here?



##########
r/R/dataset-write.R:
##########
@@ -123,7 +124,7 @@ write_dataset <- function(dataset,
                           path,
                           format = c("parquet", "feather", "arrow", "ipc", "csv"),
                           partitioning = dplyr::group_vars(dataset),
-                          basename_template = paste0("part-{i}.", as.character(format)),
+                          basename_template = NULL,

Review Comment:
   I actually don't think you need this change due to the magic of lazy evaluation, you just need to add `format <- ifelse(as.character(format) %in% c("feather", "ipc"), "arrow", format)` after `format <- match.arg(format)`
   
   ```
   > f <- function(x = c("a", "b", "c"), basename_template = paste0("part-{i}.", x)) {
   +   x <- match.arg(x)
   +   x <- toupper(x)
   +   basename_template
   + }
   > f()
   [1] "part-{i}.A"
   ```
   
   The benefit of this is that you still get to see the default value for `basename_template` in the signature/docs.
   



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