Fixed JsonVariant::isNull() not returning true after set((char*)0)

src/ArduinoJson/Variant/SlotFunctions.hpp

@@ -15,11 +15,11 @@ template <typename TAdaptedString>
 inline bool slotSetKey(VariantSlot* var, TAdaptedString key, MemoryPool* pool) {
   if (!var) return false;
   if (key.isStatic()) {
-    var->setLinkedKey(key.data());
+    var->setLinkedKey(make_not_null(key.data()));
   } else {
-    char* dup = key.save(pool);
+    const char* dup = key.save(pool);
     if (!dup) return false;
-    var->setOwnedKey(dup);
+    var->setOwnedKey(make_not_null(dup));
   }
   return true;
 }

src/ArduinoJson/Variant/VariantData.hpp

@@ -5,6 +5,7 @@
 #pragma once
 
 #include "../Misc/SerializedValue.hpp"
+#include "../Polyfills/gsl/not_null.hpp"
 #include "VariantContent.hpp"
 
 namespace ARDUINOJSON_NAMESPACE {
@@ -179,9 +180,13 @@ class VariantData {
   }
 
   void setLinkedRaw(SerializedValue<const char *> value) {
-    setType(VALUE_IS_LINKED_RAW);
-    _content.asRaw.data = value.data();
-    _content.asRaw.size = value.size();
+    if (value.data()) {
+      setType(VALUE_IS_LINKED_RAW);
+      _content.asRaw.data = value.data();
+      _content.asRaw.size = value.size();
+    } else {
+      setType(VALUE_IS_NULL);
+    }
   }
 
   template <typename T>
@@ -220,25 +225,26 @@ class VariantData {
   }
 
   void setLinkedString(const char *value) {
-    setType(VALUE_IS_LINKED_STRING);
-    _content.asString = value;
+    if (value) {
+      setType(VALUE_IS_LINKED_STRING);
+      _content.asString = value;
+    } else {
+      setType(VALUE_IS_NULL);
+    }
   }
 
   void setNull() {
     setType(VALUE_IS_NULL);
   }
 
-  void setOwnedString(const char *s) {
+  void setOwnedString(not_null<const char *> s) {
     setType(VALUE_IS_OWNED_STRING);
-    _content.asString = s;
+    _content.asString = s.get();
   }
 
-  template <typename T>
-  bool setOwnedString(T value, MemoryPool *pool) {
-    char *dup = value.save(pool);
-    if (dup) {
-      setType(VALUE_IS_OWNED_STRING);
-      _content.asString = dup;
+  bool setOwnedString(const char *s) {
+    if (s) {
+      setOwnedString(make_not_null(s));
       return true;
     } else {
       setType(VALUE_IS_NULL);
@@ -246,6 +252,11 @@ class VariantData {
     }
   }
 
+  template <typename T>
+  bool setOwnedString(T value, MemoryPool *pool) {
+    return setOwnedString(value.save(pool));
+  }
+
   void setUnsignedInteger(UInt value) {
     setType(VALUE_IS_POSITIVE_INTEGER);
     _content.asInteger = static_cast<UInt>(value);

src/ArduinoJson/Variant/VariantSlot.hpp

@@ -4,6 +4,7 @@
 
 #pragma once
 
+#include "../Polyfills/gsl/not_null.hpp"
 #include "../Polyfills/type_traits.hpp"
 #include "../Variant/VariantContent.hpp"
 
@@ -67,14 +68,14 @@ class VariantSlot {
     _next = VariantSlotDiff(slot - this);
   }
 
-  void setOwnedKey(const char* k) {
+  void setOwnedKey(not_null<const char*> k) {
     _flags |= KEY_IS_OWNED;
-    _key = k;
+    _key = k.get();
   }
 
-  void setLinkedKey(const char* k) {
+  void setLinkedKey(not_null<const char*> k) {
     _flags &= VALUE_MASK;
-    _key = k;
+    _key = k.get();
   }
 
   const char* key() const {