Fix (u)int8 implicit char conversion in stringstream (#5445)

This PR fixes the implicit character conversion that occurs when writing
a `(u)int8` value to a `stringstream` in the helper function
`std::string to_str(const T& value)`. By casting to `(u)int32`, we avoid
this conversion.

This issue was discovered after encountering a `UnicodeDecodeError` when
using `operator<<` in the TileDB-Py API on a TileDB Array schema that
contained a `(u)int8` attribute. Both a minimal TileDB-Py reproduction
and the original issue involving TileDB-SOMA now work as expected.

[sc-61915]

---
TYPE: NO_HISTORY | BUG
DESC: Fix implicit character conversion in `to_str` by casting (u)int8
to (u)int32.

---------

Co-authored-by: Theodore Tsirpanis <[email protected]>

tiledb/sm/misc/parse_argument.cc

@@ -241,10 +241,12 @@ std::string to_str(const void* value, Datatype type) {
   std::stringstream ss;
   switch (type) {
     case Datatype::INT8:
-      ss << *(const int8_t*)value;
+      // cast to int32 to avoid char conversion to ASCII
+      ss << static_cast<int32_t>(*(const int8_t*)value);
       break;
     case Datatype::UINT8:
-      ss << *(const uint8_t*)value;
+      // cast to uint32 to avoid char conversion to ASCII
+      ss << static_cast<uint32_t>(*(const uint8_t*)value);
       break;
     case Datatype::INT16:
       ss << *(const int16_t*)value;

tiledb/sm/misc/test/CMakeLists.txt

@@ -36,6 +36,7 @@ commence(unit_test misc)
         unit_hilbert.cc
         unit_integral_type_casts.cc
         unit_math.cc
+        unit_parse_argument.cc
     )
 conclude(unit_test)
 

tiledb/sm/misc/test/unit_parse_argument.cc

@@ -0,0 +1,64 @@
+/**
+ * @file unit_parse_argument.cc
+ *
+ * @section LICENSE
+ *
+ * The MIT License
+ *
+ * @copyright Copyright (c) 2025 TileDB, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ *
+ * @section DESCRIPTION
+ *
+ * Tests for useful (global) functions.
+ */
+
+#include "catch.hpp"
+#include "tiledb/sm/enums/datatype.h"
+#include "tiledb/sm/misc/parse_argument.h"
+
+using namespace tiledb::sm::utils::parse;
+using namespace tiledb::sm;
+
+TEST_CASE("Test to_str function for integers", "[to_str][integer]") {
+  int8_t int8_value = -10;
+  uint8_t uint8_value = 10;
+
+  REQUIRE(to_str(&int8_value, Datatype::INT8) == "-10");
+  REQUIRE(to_str(&uint8_value, Datatype::UINT8) == "10");
+
+  int16_t int16_value = -10;
+  uint16_t uint16_value = 10;
+
+  REQUIRE(to_str(&int16_value, Datatype::INT16) == "-10");
+  REQUIRE(to_str(&uint16_value, Datatype::UINT16) == "10");
+
+  int32_t int32_value = -10;
+  uint32_t uint32_value = 10;
+
+  REQUIRE(to_str(&int32_value, Datatype::INT32) == "-10");
+  REQUIRE(to_str(&uint32_value, Datatype::UINT32) == "10");
+
+  int64_t int64_value = -10;
+  uint64_t uint64_value = 10;
+
+  REQUIRE(to_str(&int64_value, Datatype::INT64) == "-10");
+  REQUIRE(to_str(&uint64_value, Datatype::UINT64) == "10");
+}