GH-50852: [C++][FlightRPC][ODBC] Decode wide connection/descriptor string attributes with the wide decoder

SetConnectAttr(SQL_ATTR_CURRENT_CATALOG) had its is_unicode decode branches
swapped, and SetField(SQL_DESC_NAME) unconditionally used the byte-wise
SetAttributeUTF8. In both cases a wide SQLWCHAR buffer was misread, corrupting
the stored value. Decode wide buffers with SetAttributeSQLWCHAR, matching the
mapping the getters already use (GetStringAttribute / GetAttributeSQLWCHAR).

Add a round-trip TYPED_TEST for SQL_ATTR_CURRENT_CATALOG through the wide entry
point (connection_attr_test.cc) and a SetField/GetField round-trip unit test
for SQL_DESC_NAME (odbc_descriptor_test.cc).

Co-authored-by: Isaac

Author: vikrantpuppala

cpp/src/arrow/flight/sql/odbc/odbc_impl/CMakeLists.txt

@@ -186,6 +186,7 @@ add_arrow_test(odbc_spi_impl_test
                json_converter_test.cc
                record_batch_transformer_test.cc
                util_test.cc
+               odbc_descriptor_test.cc
                EXTRA_LINK_LIBS
                arrow_odbc_spi_impl
                ${ODBC_SPI_IMPL_TEST_LINK_LIBS})

cpp/src/arrow/flight/sql/odbc/odbc_impl/odbc_connection.cc

@@ -465,9 +465,9 @@ void ODBCConnection::SetConnectAttr(SQLINTEGER attribute, SQLPOINTER value,
     case SQL_ATTR_CURRENT_CATALOG: {
       std::string catalog;
       if (is_unicode) {
-        SetAttributeUTF8(value, string_length, catalog);
-      } else {
         SetAttributeSQLWCHAR(value, string_length, catalog);
+      } else {
+        SetAttributeUTF8(value, string_length, catalog);
       }
       if (!spi_connection_->SetAttribute(Connection::CURRENT_CATALOG, catalog)) {
         throw DriverException("Option value changed.", "01S02");

cpp/src/arrow/flight/sql/odbc/odbc_impl/odbc_descriptor.cc

@@ -215,7 +215,7 @@ void ODBCDescriptor::SetField(SQLSMALLINT record_number, SQLSMALLINT field_ident
       has_bindings_changed_ = true;
       break;
     case SQL_DESC_NAME:
-      SetAttributeUTF8(value, buffer_length, record.name);
+      SetAttributeSQLWCHAR(value, buffer_length, record.name);
       has_bindings_changed_ = true;
       break;
     case SQL_DESC_OCTET_LENGTH:

cpp/src/arrow/flight/sql/odbc/odbc_impl/odbc_descriptor_test.cc

@@ -0,0 +1,54 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+#include "arrow/flight/sql/odbc/odbc_impl/odbc_descriptor.h"
+
+#include "arrow/flight/sql/odbc/odbc_impl/diagnostics.h"
+#include "arrow/flight/sql/odbc/odbc_impl/encoding.h"
+#include "arrow/flight/sql/odbc/odbc_impl/encoding_utils.h"
+
+#include <sql.h>
+#include <sqlext.h>
+
+#include "gtest/gtest.h"
+
+namespace arrow::flight::sql::odbc {
+
+using ODBC::ODBCDescriptor;
+
+TEST(ODBCDescriptorTest, SetGetNameWideRoundTrips) {
+  arrow::flight::sql::odbc::Diagnostics diagnostics("vendor", "component",
+                                                    OdbcVersion::V_3);
+  ODBCDescriptor desc(diagnostics, nullptr, nullptr, /*is_app_descriptor=*/true,
+                      /*is_writable=*/true, /*is_2x_connection=*/false);
+
+  SQLSMALLINT count = 1;
+  desc.SetHeaderField(SQL_DESC_COUNT, reinterpret_cast<SQLPOINTER>(&count), 0);
+
+  std::vector<uint8_t> wide;
+  Utf8ToWcs("my_column", &wide);
+  desc.SetField(1, SQL_DESC_NAME, wide.data(), static_cast<SQLINTEGER>(wide.size()));
+
+  SQLWCHAR out[256];
+  SQLINTEGER out_len = 0;
+  desc.GetField(1, SQL_DESC_NAME, out, sizeof(out), &out_len);
+  std::string name =
+      ODBC::SqlWcharToString(out, static_cast<SQLSMALLINT>(out_len / GetSqlWCharSize()));
+  EXPECT_EQ("my_column", name);
+}
+
+}  // namespace arrow::flight::sql::odbc

cpp/src/arrow/flight/sql/odbc/tests/connection_attr_test.cc

@@ -410,4 +410,23 @@ TYPED_TEST(ConnectionAttributeTest, TestSQLSetConnectAttrPacketSizeValid) {
 #endif
 }
 
+// A multi-character catalog set through the wide entry point must round-trip
+// intact.
+TYPED_TEST(ConnectionAttributeTest, TestSQLSetGetConnectAttrCurrentCatalogWide) {
+  ASSIGN_SQLWCHAR_ARR_AND_LEN(catalog, L"my_catalog");
+
+  ASSERT_EQ(SQL_SUCCESS, SQLSetConnectAttr(this->conn, SQL_ATTR_CURRENT_CATALOG, catalog,
+                                           catalog_len * GetSqlWCharSize()));
+
+  SQLWCHAR out_str[kOdbcBufferSize];
+  SQLINTEGER out_str_len;
+  ASSERT_EQ(SQL_SUCCESS, SQLGetConnectAttr(this->conn, SQL_ATTR_CURRENT_CATALOG, out_str,
+                                           kOdbcBufferSize, &out_str_len));
+  // SQLGetConnectAttr returns the length in bytes; convert to characters.
+  out_str_len /= GetSqlWCharSize();
+  std::string out_catalog =
+      ODBC::SqlWcharToString(out_str, static_cast<SQLSMALLINT>(out_str_len));
+  EXPECT_EQ("my_catalog", out_catalog);
+}
+
 }  // namespace arrow::flight::sql::odbc