From c6bb2ecc8b06e6459159ae883a78af5ae2fb84ca Mon Sep 17 00:00:00 2001
From: Ruoxi Sun <zanmato1984@gmail.com>
Date: Sun, 7 Apr 2024 15:29:54 +0800
Subject: [PATCH] Fix map scalar to string

---
 cpp/src/arrow/scalar.cc      |  2 ++
 cpp/src/arrow/scalar_test.cc | 11 +++++++++++
 2 files changed, 13 insertions(+)

diff --git a/cpp/src/arrow/scalar.cc b/cpp/src/arrow/scalar.cc
index 58516801ee235..f6d07505e3db3 100644
--- a/cpp/src/arrow/scalar.cc
+++ b/cpp/src/arrow/scalar.cc
@@ -1391,6 +1391,8 @@ struct FromTypeVisitor : CastImplVisitor {
     return CastFromListLike(large_list_view_type);
   }
 
+  Status Visit(const MapType& map_type) { return CastFromListLike(map_type); }
+
   Status Visit(const NullType&) { return NotImplemented(); }
   Status Visit(const DictionaryType&) { return NotImplemented(); }
   Status Visit(const ExtensionType&) { return NotImplemented(); }
diff --git a/cpp/src/arrow/scalar_test.cc b/cpp/src/arrow/scalar_test.cc
index ea4eb145cfe37..48074750fd41e 100644
--- a/cpp/src/arrow/scalar_test.cc
+++ b/cpp/src/arrow/scalar_test.cc
@@ -1286,6 +1286,17 @@ TEST(TestMapScalar, Cast) {
   CheckListCastError(scalar, invalid_cast_type);
 }
 
+TEST(TestMapScalar, ToString) {
+  auto key_value_type = struct_({field("key", utf8(), false), field("value", int8())});
+  auto value = ArrayFromJSON(key_value_type,
+                             R"([{"key": "a", "value": 1}, {"key": "b", "value": 2}])");
+  auto scalar = MapScalar(value);
+
+  ASSERT_EQ(
+      scalar.ToString(),
+      R"(map<string, int8>[{key:string = a, value:int8 = 1}, {key:string = b, value:int8 = 2}])");
+}
+
 TEST(TestStructScalar, FieldAccess) {
   StructScalar abc({MakeScalar(true), MakeNullScalar(int32()), MakeScalar("hello"),
                     MakeNullScalar(int64())},