should be it

external/duckdb/third_party/yyjson/CMakeLists.txt

@@ -0,0 +1,17 @@
+if(POLICY CMP0063)
+    cmake_policy(SET CMP0063 NEW)
+endif()
+
+add_library(duckdb_yyjson STATIC yyjson.cpp)
+
+target_include_directories(
+        duckdb_yyjson
+        PUBLIC $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>)
+set_target_properties(duckdb_yyjson PROPERTIES EXPORT_NAME duckdb_duckdb_yyjson)
+
+install(TARGETS duckdb_yyjson
+        EXPORT "${DUCKDB_EXPORT_SET}"
+        LIBRARY DESTINATION "${INSTALL_LIB_DIR}"
+        ARCHIVE DESTINATION "${INSTALL_LIB_DIR}")
+
+disable_target_warnings(duckdb_yyjson)

external/duckdb/third_party/yyjson/LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2020 YaoYuan <ibireme@gmail.com>
+
+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.

external/duckdb/third_party/yyjson/include/yyjson_utils.hpp

@@ -0,0 +1,33 @@
+//===----------------------------------------------------------------------===//
+//                         DuckDB
+//
+// yyjson_utils.hpp
+//
+//
+//===----------------------------------------------------------------------===//
+
+#pragma once
+
+#include "yyjson.hpp"
+
+using namespace duckdb_yyjson; // NOLINT
+
+namespace duckdb {
+
+struct ConvertedJSONHolder {
+public:
+	~ConvertedJSONHolder() {
+		if (doc) {
+			yyjson_mut_doc_free(doc);
+		}
+		if (stringified_json) {
+			free(stringified_json);
+		}
+	}
+
+public:
+	yyjson_mut_doc *doc = nullptr;
+	char *stringified_json = nullptr;
+};
+
+} // namespace duckdb