From b02d979ceb3ad26a39d03f989981a8e910aa0abb Mon Sep 17 00:00:00 2001
From: Benoit Blanchon <git@benoitblanchon.fr>
Date: Mon, 14 Mar 2022 19:40:05 +0100
Subject: [PATCH] Test null

---
 extras/tests/JsonVariant/link.cpp       | 24 ++++++++++++++++++++++++
 src/ArduinoJson/Variant/VariantData.hpp |  5 +++--
 src/ArduinoJson/Variant/VariantImpl.hpp | 10 +++++++---
 3 files changed, 34 insertions(+), 5 deletions(-)

diff --git a/extras/tests/JsonVariant/link.cpp b/extras/tests/JsonVariant/link.cpp
index 6c6ebdb3..28ef2ecd 100644
--- a/extras/tests/JsonVariant/link.cpp
+++ b/extras/tests/JsonVariant/link.cpp
@@ -50,4 +50,28 @@ TEST_CASE("JsonVariant::link()") {
 
     CHECK(variant.as<std::string>() == "{\"hello\":\"WORLD!\"}");
   }
+
+  SECTION("target is unbound") {
+    JsonVariant unbound;
+    variant["hello"] = "world";
+
+    variant.link(unbound);
+
+    CHECK(variant.isUnbound() == false);
+    CHECK(variant.isNull() == true);
+    CHECK(variant.memoryUsage() == 0);
+    CHECK(variant.size() == 0);
+  }
+
+  SECTION("variant is unbound") {
+    JsonVariant unbound;
+    doc2["hello"] = "world";
+
+    unbound.link(doc2);
+
+    CHECK(unbound.isUnbound() == true);
+    CHECK(unbound.isNull() == true);
+    CHECK(unbound.memoryUsage() == 0);
+    CHECK(unbound.size() == 0);
+  }
 }
diff --git a/src/ArduinoJson/Variant/VariantData.hpp b/src/ArduinoJson/Variant/VariantData.hpp
index 7bbe746f..25652f0a 100644
--- a/src/ArduinoJson/Variant/VariantData.hpp
+++ b/src/ArduinoJson/Variant/VariantData.hpp
@@ -244,9 +244,10 @@ class VariantData {
     setType(VALUE_IS_NULL);
   }
 
-  void setPointer(const VariantData *value) {
+  void setPointer(const VariantData *p) {
+    ARDUINOJSON_ASSERT(p);
     setType(VALUE_IS_POINTER);
-    _content.asPointer = value;
+    _content.asPointer = p;
   }
 
   void setString(String s) {
diff --git a/src/ArduinoJson/Variant/VariantImpl.hpp b/src/ArduinoJson/Variant/VariantImpl.hpp
index 918f07a5..6b4a3492 100644
--- a/src/ArduinoJson/Variant/VariantImpl.hpp
+++ b/src/ArduinoJson/Variant/VariantImpl.hpp
@@ -189,9 +189,13 @@ bool CopyStringStoragePolicy::store(TAdaptedString str, MemoryPool *pool,
   return copy != 0;
 }
 
-inline void VariantRef::link(VariantConstRef var) {
-  if (_data)
-    _data->setPointer(var._data);
+inline void VariantRef::link(VariantConstRef target) {
+  if (!_data)
+    return;
+  if (target._data)
+    _data->setPointer(target._data);
+  else
+    _data->setNull();
 }
 
 }  // namespace ARDUINOJSON_NAMESPACE