Test null

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);
+  }
 }

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) {

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) {
+inline void VariantRef::link(VariantConstRef target) {
-  if (_data)
+  if (!_data)
-    _data->setPointer(var._data);
+    return;
+  if (target._data)
+    _data->setPointer(target._data);
+  else
+    _data->setNull();
 }
 
 }  // namespace ARDUINOJSON_NAMESPACE