[SPARK-17577][FOLLOW-UP][SPARKR] SparkR spark.addFile supports adding directory recursively

## What changes were proposed in this pull request?
#15140 exposed ```JavaSparkContext.addFile(path: String, recursive: Boolean)``` to Python/R, then we can update SparkR ```spark.addFile``` to support adding directory recursively.

## How was this patch tested?
Added unit test.

Author: Yanbo Liang <ybliang8@gmail.com>

Closes #15216 from yanboliang/spark-17577-2.

R/pkg/R/context.R

@@ -231,17 +231,22 @@ setCheckpointDir <- function(sc, dirName) {
 #' filesystems), or an HTTP, HTTPS or FTP URI. To access the file in Spark jobs,
 #' use spark.getSparkFiles(fileName) to find its download location.
 #'
+#' A directory can be given if the recursive option is set to true.
+#' Currently directories are only supported for Hadoop-supported filesystems.
+#' Refer Hadoop-supported filesystems at \url{https://wiki.apache.org/hadoop/HCFS}.
+#'
 #' @rdname spark.addFile
 #' @param path The path of the file to be added
+#' @param recursive Whether to add files recursively from the path. Default is FALSE.
 #' @export
 #' @examples
 #'\dontrun{
 #' spark.addFile("~/myfile")
 #'}
 #' @note spark.addFile since 2.1.0
-spark.addFile <- function(path) {
+spark.addFile <- function(path, recursive = FALSE) {
   sc <- getSparkContext()
-  invisible(callJMethod(sc, "addFile", suppressWarnings(normalizePath(path))))
+  invisible(callJMethod(sc, "addFile", suppressWarnings(normalizePath(path)), recursive))
 }
 
 #' Get the root directory that contains files added through spark.addFile.

R/pkg/inst/tests/testthat/test_context.R

@@ -169,6 +169,7 @@ test_that("spark.lapply should perform simple transforms", {
 
 test_that("add and get file to be downloaded with Spark job on every node", {
   sparkR.sparkContext()
+  # Test add file.
   path <- tempfile(pattern = "hello", fileext = ".txt")
   filename <- basename(path)
   words <- "Hello World!"
@@ -177,5 +178,26 @@ test_that("add and get file to be downloaded with Spark job on every node", {
   download_path <- spark.getSparkFiles(filename)
   expect_equal(readLines(download_path), words)
   unlink(path)
+
+  # Test add directory recursively.
+  path <- paste0(tempdir(), "/", "recursive_dir")
+  dir.create(path)
+  dir_name <- basename(path)
+  path1 <- paste0(path, "/", "hello.txt")
+  file.create(path1)
+  sub_path <- paste0(path, "/", "sub_hello")
+  dir.create(sub_path)
+  path2 <- paste0(sub_path, "/", "sub_hello.txt")
+  file.create(path2)
+  words <- "Hello World!"
+  sub_words <- "Sub Hello World!"
+  writeLines(words, path1)
+  writeLines(sub_words, path2)
+  spark.addFile(path, recursive = TRUE)
+  download_path1 <- spark.getSparkFiles(paste0(dir_name, "/", "hello.txt"))
+  expect_equal(readLines(download_path1), words)
+  download_path2 <- spark.getSparkFiles(paste0(dir_name, "/", "sub_hello/sub_hello.txt"))
+  expect_equal(readLines(download_path2), sub_words)
+  unlink(path, recursive = TRUE)
   sparkR.session.stop()
 })