fix(json_wrapper): fix undefined behavior in copy constructor

The copy constructor was checking owns_json_ and json_ before they were
initialized, causing undefined behavior. This fix initializes members
before use in the member initializer list.

Added unit tests to verify copy constructor behavior in various scenarios,
including copying non-owning wrappers from operator[].

Signed-off-by: LHT129 <tianlan.lht@antgroup.com>

Author: LHT129

src/json_wrapper.cpp

@@ -30,14 +30,11 @@ JsonWrapper::~JsonWrapper() {
     }
 }
 
-JsonWrapper::JsonWrapper(const JsonWrapper& other) {
-    if (owns_json_) {
-        delete json_;
-    }
-    json_ = new nlohmann::json();
-    owns_json_ = true;
+JsonWrapper::JsonWrapper(const JsonWrapper& other) : json_(nullptr), owns_json_(true) {
     if (other.json_ != nullptr) {
-        *json_ = *other.json_;
+        json_ = new nlohmann::json(*other.json_);
+    } else {
+        json_ = new nlohmann::json();
     }
 }
 

tests/test_json_wrapper.cpp

@@ -0,0 +1,60 @@
+// Copyright 2024-present the vsag project
+//
+// Licensed 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 <catch2/catch_test_macros.hpp>
+
+#include "json_wrapper.h"
+
+TEST_CASE("JsonWrapper Copy Empty Wrapper", "[ft][json_wrapper]") {
+    vsag::JsonWrapper w1;
+    vsag::JsonWrapper w2 = w1;
+    CHECK_FALSE(w2.Contains("any_key"));
+}
+
+TEST_CASE("JsonWrapper Copy With String Data", "[ft][json_wrapper]") {
+    auto w1 = vsag::JsonWrapper::Parse(R"({"key": "value"})");
+    vsag::JsonWrapper w2 = w1;
+    CHECK(w2.Contains("key"));
+    CHECK(w2["key"].GetString() == "value");
+}
+
+TEST_CASE("JsonWrapper Copy With Integer Data", "[ft][json_wrapper]") {
+    auto w1 = vsag::JsonWrapper::Parse(R"({"num": 42})");
+    vsag::JsonWrapper w2 = w1;
+    CHECK(w2.Contains("num"));
+    CHECK(w2["num"].GetInt() == 42);
+}
+
+TEST_CASE("JsonWrapper Copy Independence", "[ft][json_wrapper]") {
+    auto w1 = vsag::JsonWrapper::Parse(R"({"key": "value1"})");
+    vsag::JsonWrapper w2 = w1;
+    w2["key"].SetString("value2");
+    CHECK(w1["key"].GetString() == "value1");
+    CHECK(w2["key"].GetString() == "value2");
+}
+
+TEST_CASE("JsonWrapper Copy Nested Json", "[ft][json_wrapper]") {
+    auto w1 = vsag::JsonWrapper::Parse(R"({"outer": {"inner": "data"}})");
+    vsag::JsonWrapper w2 = w1;
+    CHECK(w2.Contains("outer"));
+    CHECK(w2["outer"].Contains("inner"));
+    CHECK(w2["outer"]["inner"].GetString() == "data");
+}
+
+TEST_CASE("JsonWrapper Copy Non-owning Wrapper", "[ft][json_wrapper]") {
+    auto w1 = vsag::JsonWrapper::Parse(R"({"valid": "json"})");
+    vsag::JsonWrapper sub = w1["valid"];
+    vsag::JsonWrapper w2 = sub;
+    CHECK(w2.GetString() == "json");
+}