[arrow] branch main updated: GH-38376 [R]: Add `dimnames` method to `Dataset` class (#38377)

[thisisnic]

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The following commit(s) were added to refs/heads/main by this push:
     new f489996e70 GH-38376 [R]: Add `dimnames` method to `Dataset` class  
(#38377)
f489996e70 is described below

commit f489996e707dd136e41f1eb8ed963f707eed18ad
Author: Jonathan Keane <jke...@gmail.com>
AuthorDate: Sun Oct 22 12:18:33 2023 -0500

    GH-38376 [R]: Add `dimnames` method to `Dataset` class  (#38377)
    
    ### Rationale for this change
    
    Add `dimnames` method so that things like `colnames(ds)` work out of the 
box on datasets. Inspired by dbplyr's lazy tbl implementation
    
    ### What changes are included in this PR?
    
    An additional `dimnames` method for Dataset objects
    
    ### Are these changes tested?
    
    Yes
    
    ### Are there any user-facing changes?
    
    Yes
    * Closes: #38376
    
    Authored-by: Jonathan Keane <jke...@gmail.com>
    Signed-off-by: Nic Crane <thisis...@gmail.com>
---
 r/NAMESPACE                     | 1 +
 r/R/dataset.R                   | 3 +++
 r/tests/testthat/test-dataset.R | 6 ++++++
 3 files changed, 10 insertions(+)

diff --git a/r/NAMESPACE b/r/NAMESPACE
index dac2cbda9c..412d70ed22 100644
--- a/r/NAMESPACE
+++ b/r/NAMESPACE
@@ -101,6 +101,7 @@ S3method(dim,RecordBatchReader)
 S3method(dim,StructArray)
 S3method(dim,arrow_dplyr_query)
 S3method(dimnames,ArrowTabular)
+S3method(dimnames,Dataset)
 S3method(head,ArrowDatum)
 S3method(head,ArrowTabular)
 S3method(head,Dataset)
diff --git a/r/R/dataset.R b/r/R/dataset.R
index 2400d08393..682f6c1481 100644
--- a/r/R/dataset.R
+++ b/r/R/dataset.R
@@ -527,6 +527,9 @@ names.Dataset <- function(x) names(x$schema)
 #' @export
 dim.Dataset <- function(x) c(x$num_rows, x$num_cols)
 
+#' @export
+dimnames.Dataset <- function(x) list(NULL, names(x))
+
 #' @export
 c.Dataset <- function(...) Dataset$create(list(...))
 
diff --git a/r/tests/testthat/test-dataset.R b/r/tests/testthat/test-dataset.R
index b7632084e4..7ea47db449 100644
--- a/r/tests/testthat/test-dataset.R
+++ b/r/tests/testthat/test-dataset.R
@@ -334,6 +334,12 @@ test_that("dim method returns the correct number of rows 
and columns", {
   expect_identical(dim(ds), c(20L, 7L))
 })
 
+test_that("dimnames, colnames on Dataset objects", {
+  ds <- open_dataset(dataset_dir, partitioning = schema(part = uint8()))
+  col_names <- c("int", "dbl", "lgl", "chr", "fct", "ts", "part")
+  expect_identical(dimnames(ds), list(NULL, col_names))
+  expect_identical(colnames(ds), col_names)
+})
 
 test_that("dim() correctly determine numbers of rows and columns on 
arrow_dplyr_query object", {
   ds <- open_dataset(dataset_dir, partitioning = schema(part = uint8()))