[GitHub] [arrow] nealrichardson commented on a diff in pull request #14679: ARROW-15470: [R] Set null value in CSV writer

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

nealrichardson commented on code in PR #14679:
URL: https://github.com/apache/arrow/pull/14679#discussion_r1027095501


##########
r/R/csv.R:
##########
@@ -418,6 +418,8 @@ CsvTableReader$create <- function(file,
 #' The `CsvWriteOptions$create()` factory method takes the following arguments:
 #' - `include_header` Whether to write an initial header line with column names
 #' - `batch_size` Maximum number of rows processed at a time. Default is 1024.
+#' - `null_string` The string to be written for null values. Must not contain
+#'   quotation marks. Default is `NA`.

Review Comment:
   Is this the current default, or is this a behavior change?



##########
r/R/csv.R:
##########
@@ -456,24 +458,31 @@ CsvReadOptions$create <- function(use_threads = option_use_threads(),
 }
 
 readr_to_csv_write_options <- function(include_header,
-                                       batch_size = 1024L) {
+                                       batch_size = 1024L,
+                                       na = "NA") {
   assert_that(is_integerish(batch_size, n = 1, finite = TRUE), batch_size > 0)
   assert_that(is.logical(include_header))
+  assert_that(is.character(na))
+  assert_that(length(na) == 1)
+  assert_that(!grepl('"', na), msg = "na argument must not contain quote characters.")

Review Comment:
   Only `"` is invalid? What about `'`?



##########
r/tests/testthat/test-csv.R:
##########
@@ -422,6 +422,25 @@ test_that("Write a CSV file with invalid batch size", {
   )
 })
 
+test_that("Write a CSV with custom NA value", {
+  tbl_out1 <- write_csv_arrow(tbl_no_dates, csv_file, na = "NULL_VALUE")

Review Comment:
   Is it worth adding a test that `na = ""` works? I'd imagine that would be a common choice,. 



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