Set parent pointers for values inserted via update() (fixes #3007).

include/nlohmann/json.hpp

@@ -6009,6 +6009,9 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         for (auto it = j.cbegin(); it != j.cend(); ++it)
         {
             m_value.object->operator[](it.key()) = it.value();
+#if JSON_DIAGNOSTICS
+            m_value.object->operator[](it.key()).m_parent = this;
+#endif
         }
     }
 

single_include/nlohmann/json.hpp

@@ -23414,6 +23414,9 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         for (auto it = j.cbegin(); it != j.cend(); ++it)
         {
             m_value.object->operator[](it.key()) = it.value();
+#if JSON_DIAGNOSTICS
+            m_value.object->operator[](it.key()).m_parent = this;
+#endif
         }
     }
 

test/src/unit-diagnostics.cpp

@@ -34,6 +34,7 @@ SOFTWARE.
 #endif
 
 #define JSON_DIAGNOSTICS 1
+#define JSON_TESTS_PRIVATE
 
 #include <nlohmann/json.hpp>
 using nlohmann::json;
@@ -184,4 +185,21 @@ TEST_CASE("Better diagnostics")
         j["second"] = value;
         j2["something"] = j;
     }
+
+    SECTION("Regression test for issue #3007 - Parent pointers properly set when using update()")
+    {
+        json j = json::object();
+
+        {
+            json j2 = json::object();
+            j2["one"] = 1;
+
+            j.update(j2);
+        }
+
+        for (auto const& kv : j)
+        {
+            CHECK(kv.m_parent == &j);
+        }
+    }
 }