From ded44ac3a928a78c8c435ddfa407e029e877ad1a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Drago=C8=99=20Moldovan-Gr=C3=BCnfeld?=
 <dragos.mold@gmail.com>
Date: Thu, 17 Feb 2022 09:51:55 +0000
Subject: [PATCH 1/2] add & export type method for `Expression` + unit test

---
 r/NAMESPACE                  |  1 +
 r/R/type.R                   |  3 +++
 r/tests/testthat/test-type.R | 10 ++++++++++
 3 files changed, 14 insertions(+)

diff --git a/r/NAMESPACE b/r/NAMESPACE
index f91fe20ccaa..aa487cf60ac 100644
--- a/r/NAMESPACE
+++ b/r/NAMESPACE
@@ -96,6 +96,7 @@ S3method(tail,RecordBatchReader)
 S3method(tail,Scanner)
 S3method(tail,arrow_dplyr_query)
 S3method(type,ArrowDatum)
+S3method(type,Expression)
 S3method(type,default)
 S3method(unique,ArrowDatum)
 S3method(vec_ptype_abbr,arrow_fixed_size_binary)
diff --git a/r/R/type.R b/r/R/type.R
index c84f1c18fbc..f8b408e4065 100644
--- a/r/R/type.R
+++ b/r/R/type.R
@@ -77,6 +77,9 @@ type.default <- function(x) Array__infer_type(x)
 #' @export
 type.ArrowDatum <- function(x) x$type
 
+#' @export
+type.Expression <- function(x) x$type
+
 #----- metadata
 
 #' @title class arrow::FixedWidthType
diff --git a/r/tests/testthat/test-type.R b/r/tests/testthat/test-type.R
index b9613d651a9..19ce976035f 100644
--- a/r/tests/testthat/test-type.R
+++ b/r/tests/testthat/test-type.R
@@ -229,3 +229,13 @@ test_that("Type strings are correctly canonicalized", {
     "Unrecognized"
   )
 })
+
+test_that("type() gets the right type for Expression", {
+  x <- Expression$field_ref("x")
+  y <- Expression$field_ref("y")
+  y$schema <- Schema$create(y = float64())
+  x$schema <- Schema$create(x = int32())
+
+  b <- Expression$create("add_checked", x, y)
+  expect_equal(b$type, type(b))
+})

From 24a4a39255fa5c230c85893acf2f5eb79c2181a9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Drago=C8=99=20Moldovan-Gr=C3=BCnfeld?=
 <dragos.mold@gmail.com>
Date: Thu, 17 Feb 2022 10:36:29 +0000
Subject: [PATCH 2/2] update unit tests

---
 r/tests/testthat/test-type.R | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/r/tests/testthat/test-type.R b/r/tests/testthat/test-type.R
index 19ce976035f..168cdcff690 100644
--- a/r/tests/testthat/test-type.R
+++ b/r/tests/testthat/test-type.R
@@ -231,11 +231,11 @@ test_that("Type strings are correctly canonicalized", {
 })
 
 test_that("type() gets the right type for Expression", {
-  x <- Expression$field_ref("x")
-  y <- Expression$field_ref("y")
-  y$schema <- Schema$create(y = float64())
-  x$schema <- Schema$create(x = int32())
+  x <- Expression$scalar(32L)
+  y <- Expression$scalar(10)
+  add_xy <- Expression$create("add", x, y)
 
-  b <- Expression$create("add_checked", x, y)
-  expect_equal(b$type, type(b))
+  expect_equal(x$type, type(x))
+  expect_equal(y$type, type(y))
+  expect_equal(add_xy$type, type(add_xy))
 })