From 1dd3ec2fe99e986dcb67335f0543b18f1904bc86 Mon Sep 17 00:00:00 2001
From: Rok Mihevc <rok@mihevc.org>
Date: Thu, 26 Sep 2024 13:31:53 +0200
Subject: [PATCH] Review feedback

---
 cpp/src/arrow/extension/json.cc |  8 ++++++--
 cpp/src/arrow/extension/json.h  |  2 ++
 cpp/src/parquet/arrow/schema.cc | 10 ++++------
 3 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/cpp/src/arrow/extension/json.cc b/cpp/src/arrow/extension/json.cc
index 6c924a47b841f..9dc1cfe6a3617 100644
--- a/cpp/src/arrow/extension/json.cc
+++ b/cpp/src/arrow/extension/json.cc
@@ -47,10 +47,14 @@ std::shared_ptr<Array> JsonExtensionType::MakeArray(
   return std::make_shared<ExtensionArray>(data);
 }
 
+bool JsonExtensionType::IsSupportedStorageType(Type::type type_id) {
+  return type_id == Type::STRING || type_id == Type::STRING_VIEW ||
+         type_id == Type::LARGE_STRING;
+}
+
 Result<std::shared_ptr<DataType>> JsonExtensionType::Make(
     std::shared_ptr<DataType> storage_type) {
-  if (storage_type->id() != Type::STRING && storage_type->id() != Type::STRING_VIEW &&
-      storage_type->id() != Type::LARGE_STRING) {
+  if (!IsSupportedStorageType(storage_type->id())) {
     return Status::Invalid("Invalid storage type for JsonExtensionType: ",
                            storage_type->ToString());
   }
diff --git a/cpp/src/arrow/extension/json.h b/cpp/src/arrow/extension/json.h
index 85f9092d62b1a..89976c8073fac 100644
--- a/cpp/src/arrow/extension/json.h
+++ b/cpp/src/arrow/extension/json.h
@@ -47,6 +47,8 @@ class ARROW_EXPORT JsonExtensionType : public ExtensionType {
 
   static Result<std::shared_ptr<DataType>> Make(std::shared_ptr<DataType> storage_type);
 
+  static bool IsSupportedStorageType(Type::type type_id);
+
  private:
   std::shared_ptr<DataType> storage_type_;
 };
diff --git a/cpp/src/parquet/arrow/schema.cc b/cpp/src/parquet/arrow/schema.cc
index f33f4681512c0..c06d2c575c89f 100644
--- a/cpp/src/parquet/arrow/schema.cc
+++ b/cpp/src/parquet/arrow/schema.cc
@@ -997,9 +997,8 @@ Result<bool> ApplyOriginalMetadata(const Field& origin_field, SchemaField* infer
     const auto& ex_type = checked_cast<const ::arrow::ExtensionType&>(*origin_type);
     if (inferred_type->id() != ::arrow::Type::EXTENSION &&
         ex_type.extension_name() == std::string("arrow.json") &&
-        (inferred_type->id() == ::arrow::Type::STRING ||
-         inferred_type->id() == ::arrow::Type::LARGE_STRING ||
-         inferred_type->id() == ::arrow::Type::STRING_VIEW)) {
+        ::arrow::extension::JsonExtensionType::IsSupportedStorageType(
+            inferred_type->storage_id())) {
       // Schema mismatch.
       //
       // Arrow extensions are DISABLED in Parquet.
@@ -1019,9 +1018,8 @@ Result<bool> ApplyOriginalMetadata(const Field& origin_field, SchemaField* infer
       // from the Parquet type
       if (ex_type.storage_type()->Equals(*inferred->field->type()) ||
           ((ex_type.extension_name() == "arrow.json") &&
-           (inferred->field->type()->storage_id() == ::arrow::Type::STRING ||
-            inferred->field->type()->storage_id() == ::arrow::Type::LARGE_STRING ||
-            inferred->field->type()->storage_id() == ::arrow::Type::STRING_VIEW))) {
+           ::arrow::extension::JsonExtensionType::IsSupportedStorageType(
+               inferred_type->storage_id()))) {
         inferred->field = inferred->field->WithType(origin_type);
       }
     }