ARROW-8433: [R] Add feather alias for ipc format in dataset API

Closes #6920 from nealrichardson/feather-dataset

Authored-by: Neal Richardson <neal.p.richardson@gmail.com>
Signed-off-by: Wes McKinney <wesm+git@apache.org>

r/R/dataset.R

@@ -123,8 +123,8 @@ open_dataset <- function(sources,
 #' * `filesystem`: A [FileSystem]
 #' * `selector`: A [FileSelector]
 #' * `format`: A string identifier of the format of the files in `path`.
-#'   Currently supported options are "parquet", "arrow", and "ipc" (an alias for
-#'   the Arrow file format)
+#'   Currently "parquet" and "ipc"/"arrow"/"feather" (aliases for each other)
+#'   are supported. For Feather, only version 2 files are supported.
 #' @section Methods:
 #'
 #' A `Dataset` has the following methods:
@@ -269,7 +269,7 @@ DatasetFactory <- R6Class("DatasetFactory", inherit = ArrowObject,
 )
 DatasetFactory$create <- function(x,
                                   filesystem = c("auto", "local"),
-                                  format = c("parquet", "arrow", "ipc"),
+                                  format = c("parquet", "arrow", "ipc", "feather"),
                                   partitioning = NULL,
                                   allow_not_found = FALSE,
                                   recursive = TRUE,
@@ -334,8 +334,8 @@ DatasetFactory$create <- function(x,
 #' @param filesystem A string identifier for the filesystem corresponding to
 #' `x`. Currently only "local" is supported.
 #' @param format A string identifier of the format of the files in `x`.
-#' Currently supported options are "parquet", "arrow", and "ipc" (an alias for
-#' the Arrow file format)
+#' Currently "parquet" and "ipc"/"arrow"/"feather" (aliases for each other)
+#' are supported. For Feather, only version 2 files are supported.
 #' @param partitioning One of
 #'   * A `Schema`, in which case the file paths relative to `sources` will be
 #'    parsed, and path segments will be matched with the schema fields. For
@@ -400,8 +400,8 @@ FileSystemDatasetFactory$create <- function(filesystem,
 #' @section Factory:
 #' `FileFormat$create()` takes the following arguments:
 #' * `format`: A string identifier of the format of the files in `path`.
-#'   Currently supported options are "parquet", "arrow", and "ipc" (an alias for
-#'   the Arrow file format)
+#'   Currently "parquet" and "ipc"/"arrow"/"feather" (aliases for each other)
+#'   are supported. For Feather, only version 2 files are supported.
 #' * `...`: Additional format-specific options
 #'   format="parquet":
 #'   * `use_buffered_stream`: Read files through buffered input streams rather than
@@ -436,7 +436,7 @@ FileFormat <- R6Class("FileFormat", inherit = ArrowObject,
 FileFormat$create <- function(format, ...) {
   if (format == "parquet") {
     ParquetFileFormat$create(...)
-  } else if (format %in% c("ipc", "arrow")) { # These are aliases for the same thing
+  } else if (format %in% c("ipc", "arrow", "feather")) { # These are aliases for the same thing
     shared_ptr(IpcFileFormat, dataset___IpcFileFormat__Make())
   } else {
     stop("Unsupported file format: ", format, call. = FALSE)

r/tests/testthat/test-dataset.R

@@ -65,8 +65,8 @@ test_that("Setup (putting data in the dir)", {
   # Now, an IPC format dataset
   dir.create(file.path(ipc_dir, 3))
   dir.create(file.path(ipc_dir, 4))
-  write_arrow(df1, file.path(ipc_dir, 3, "file1.arrow"))
-  write_arrow(df2, file.path(ipc_dir, 4, "file2.arrow"))
+  write_feather(df1, file.path(ipc_dir, 3, "file1.arrow"))
+  write_feather(df2, file.path(ipc_dir, 4, "file2.arrow"))
   expect_length(dir(ipc_dir, recursive = TRUE), 2)
 })
 
@@ -167,8 +167,8 @@ test_that("Partitioning inference", {
   )
 })
 
-test_that("IPC/Arrow format data", {
-  ds <- open_dataset(ipc_dir, partitioning = "part", format = "arrow")
+test_that("IPC/Feather format data", {
+  ds <- open_dataset(ipc_dir, partitioning = "part", format = "feather")
   expect_identical(names(ds), c(names(df1), "part"))
   expect_warning(
     dim(ds),