GH-51659: [R] Expose ignore_extra_columns and pad_short_rows CSV pars…

r/NEWS.md

@@ -27,6 +27,9 @@
   unnested. Similarly, `int64` and `uint32` values inside list columns are
   converted to a single R type across the column (#50514).
 
+- `csv_parse_options()` and `CsvParseOptions$create()` gain `pad_short_rows` and
+  `ignore_extra_columns`, exposing the new C++ parse options (#51659).
+
 # arrow 25.0.1
 
 ## Minor improvements and fixes

r/R/csv.R

@@ -722,6 +722,10 @@ readr_to_csv_read_options <- function(skip = 0, col_names = TRUE) {
 #'    and LF (`0x0a`) characters?
 #' @param ignore_empty_lines Logical: should empty lines be ignored (default) or
 #'    generate a row of missing values (if `FALSE`)?
+#' @param pad_short_rows Logical: should rows with fewer columns than expected be
+#'    padded with missing values (default `FALSE`) or raise an error?
+#' @param ignore_extra_columns Logical: should columns beyond the number expected be
+#'    ignored (default `FALSE`) or raise an error?
 #' @examplesIf arrow_with_dataset()
 #' tf <- tempfile()
 #' on.exit(unlink(tf))
@@ -737,7 +741,9 @@ csv_parse_options <- function(
   escaping = FALSE,
   escape_char = "\\",
   newlines_in_values = FALSE,
-  ignore_empty_lines = TRUE
+  ignore_empty_lines = TRUE,
+  pad_short_rows = FALSE,
+  ignore_extra_columns = FALSE
 ) {
   csv___ParseOptions__initialize(
     list(
@@ -748,7 +754,9 @@ csv_parse_options <- function(
       escaping = escaping,
       escape_char = escape_char,
       newlines_in_values = newlines_in_values,
-      ignore_empty_lines = ignore_empty_lines
+      ignore_empty_lines = ignore_empty_lines,
+      pad_short_rows = pad_short_rows,
+      ignore_extra_columns = ignore_extra_columns
     )
   )
 }

r/src/csv.cpp

@@ -68,6 +68,8 @@ std::shared_ptr<arrow::csv::ParseOptions> csv___ParseOptions__initialize(
   res->escape_char = cpp11::as_cpp<char>(options["escape_char"]);
   res->newlines_in_values = cpp11::as_cpp<bool>(options["newlines_in_values"]);
   res->ignore_empty_lines = cpp11::as_cpp<bool>(options["ignore_empty_lines"]);
+  res->pad_short_rows = cpp11::as_cpp<bool>(options["pad_short_rows"]);
+  res->ignore_extra_columns = cpp11::as_cpp<bool>(options["ignore_extra_columns"]);
   return res;
 }
 

r/tests/testthat/test-csv.R

@@ -691,6 +691,54 @@ test_that("CSV reading/parsing/convert options can be passed in as lists", {
   expect_equal(tab1, tab2)
 })
 
+test_that("pad_short_rows and ignore_extra_columns parse options", {
+  # Rows with fewer columns than expected are padded with nulls (GH-50925), and
+  # extra columns are dropped (GH-50967).
+  short <- I("a,b,c\n1,2,9\n3")
+  expect_error(read_csv_arrow(short))
+  expect_identical(
+    read_csv_arrow(short, parse_options = csv_parse_options(pad_short_rows = TRUE)),
+    tibble::tibble(a = c(1L, 3L), b = c(2L, NA), c = c(9L, NA))
+  )
+
+  extra <- I("a,b\n1,2,3\n4,5")
+  expect_error(read_csv_arrow(extra))
+  expect_identical(
+    read_csv_arrow(extra, parse_options = csv_parse_options(ignore_extra_columns = TRUE)),
+    tibble::tibble(a = c(1L, 4L), b = c(2L, 5L))
+  )
+
+  # Both together
+  ragged <- I("a,b\n1,2,3\n4")
+  expect_identical(
+    read_csv_arrow(
+      ragged,
+      parse_options = csv_parse_options(pad_short_rows = TRUE, ignore_extra_columns = TRUE)
+    ),
+    tibble::tibble(a = c(1L, 4L), b = c(2L, NA))
+  )
+
+  # The options are also accepted as a plain list, and via the R6 constructor.
+  expected <- tibble::tibble(a = c(1L, 4L), b = c(2L, NA))
+  expect_identical(
+    read_csv_arrow(
+      ragged,
+      parse_options = list(pad_short_rows = TRUE, ignore_extra_columns = TRUE)
+    ),
+    expected
+  )
+  expect_identical(
+    read_csv_arrow(
+      ragged,
+      parse_options = CsvParseOptions$create(
+        pad_short_rows = TRUE,
+        ignore_extra_columns = TRUE
+      )
+    ),
+    expected
+  )
+})
+
 test_that("Read literal data directly", {
   expected <- tibble::tibble(x = c(1L, 3L), y = c(2L, 4L))