ARROW-13171: [R] Add binding for str_pad()

r/R/dplyr-functions.R

@@ -414,6 +414,27 @@ nse_funcs$pmax <- function(..., na.rm = FALSE) {
   )
 }
 
+nse_funcs$str_pad <- function(string, width, side = c("left", "right", "both"), pad = " ") {
+
+  assert_that(is_integerish(width))
+  side <- match.arg(side)
+  assert_that(is.string(pad))
+
+  if (side == "left") {
+    pad_func = "utf8_lpad"
+  } else if (side == "right") {
+    pad_func = "utf8_rpad"
+  } else if (side == "both") {
+    pad_func = "utf8_center"
+  }
+
+  Expression$create(
+    pad_func,
+    string,
+    options = list(width = width, padding = pad)
+  )
+}
+
 # String function helpers
 
 # format `pattern` as needed for case insensitivity and literal matching by RE2

r/R/expression.R

@@ -30,6 +30,7 @@
   "str_length" = "utf8_length",
   "str_to_lower" = "utf8_lower",
   "str_to_upper" = "utf8_upper",
+  # str_pad is defined in dplyr-functions.R
   "str_reverse" = "utf8_reverse",
   # str_trim is defined in dplyr-functions.R
   "year" = "year",

r/src/compute.cpp

@@ -285,6 +285,14 @@ std::shared_ptr<arrow::compute::FunctionOptions> make_compute_options(
                                      max_splits, reverse);
   }
 
+  if (func_name == "utf8_lpad" || func_name == "utf8_rpad" ||
+      func_name == "utf8_center" || func_name == "ascii_lpad" ||
+      func_name == "ascii_rpad" || func_name == "ascii_center") {
+    using Options = arrow::compute::PadOptions;
+    return std::make_shared<Options>(cpp11::as_cpp<int64_t>(options["width"]),
+                                     cpp11::as_cpp<std::string>(options["padding"]));
+  }
+
   if (func_name == "utf8_split_whitespace" || func_name == "ascii_split_whitespace") {
     using Options = arrow::compute::SplitOptions;
     int64_t max_splits = -1;

r/tests/testthat/test-dplyr-string-functions.R

@@ -866,3 +866,44 @@ test_that("str_like", {
     df
   )
 })
+
+test_that("str_pad", {
+
+  df <- tibble(x = c("Foo and bar", "baz and qux and quux"))
+
+  expect_dplyr_equal(
+    input %>%
+      mutate(x = str_pad(x, width = 31)) %>%
+      collect(),
+    df
+  )
+
+  expect_dplyr_equal(
+    input %>%
+      mutate(x = str_pad(x, width = 30, side = "right")) %>%
+      collect(),
+    df
+  )
+
+  expect_dplyr_equal(
+    input %>%
+      mutate(x = str_pad(x, width = 31, side = "left", pad = "+")) %>%
+      collect(),
+    df
+  )
+
+  expect_dplyr_equal(
+    input %>%
+      mutate(x = str_pad(x, width = 10, side = "left", pad = "+")) %>%
+      collect(),
+    df
+  )
+
+  expect_dplyr_equal(
+    input %>%
+      mutate(x = str_pad(x, width = 31, side = "both")) %>%
+      collect(),
+    df
+  )
+
+})