update ArduinoJson to 6.19.4

lib/ArduinoJson/src/ArduinoJson/Array/ElementProxy.hpp

@@ -118,6 +118,10 @@ class ElementProxy : public VariantOperators<ElementProxy<TArray> >,
     return getUpstreamElement().size();
   }
 
+  FORCE_INLINE size_t memoryUsage() const {
+    return getUpstreamElement().memoryUsage();
+  }
+
   template <typename TNestedKey>
   VariantRef getMember(TNestedKey* key) const {
     return getUpstreamElement().getMember(key);

lib/ArduinoJson/src/ArduinoJson/Document/JsonDocument.hpp

@@ -14,7 +14,8 @@
 
 namespace ARDUINOJSON_NAMESPACE {
 
-class JsonDocument : public Visitable {
+class JsonDocument : public Visitable,
+                     public VariantOperators<const JsonDocument&> {
  public:
   template <typename TVisitor>
   typename TVisitor::result_type accept(TVisitor& visitor) const {
@@ -295,16 +296,12 @@ class JsonDocument : public Visitable {
     _data.remove(adaptString(key));
   }
 
+  FORCE_INLINE operator VariantRef() {
+    return getVariant();
+  }
+
   FORCE_INLINE operator VariantConstRef() const {
-    return VariantConstRef(&_data);
-  }
-
-  bool operator==(VariantConstRef rhs) const {
-    return getVariant() == rhs;
-  }
-
-  bool operator!=(VariantConstRef rhs) const {
-    return getVariant() != rhs;
+    return getVariant();
   }
 
  protected:

lib/ArduinoJson/src/ArduinoJson/Object/MemberProxy.hpp

@@ -94,6 +94,10 @@ class MemberProxy : public VariantOperators<MemberProxy<TObject, TStringRef> >,
     return getUpstreamMember().size();
   }
 
+  FORCE_INLINE size_t memoryUsage() const {
+    return getUpstreamMember().memoryUsage();
+  }
+
   FORCE_INLINE void remove(size_t index) const {
     getUpstreamMember().remove(index);
   }

lib/ArduinoJson/src/ArduinoJson/Variant/VariantCompare.hpp

@@ -131,9 +131,9 @@ struct RawComparer : ComparerBase {
 template <typename T>
 struct Comparer<T, typename enable_if<IsVisitable<T>::value>::type>
     : ComparerBase {
-  T rhs;
+  const T *rhs;  // TODO: should be a VariantConstRef
 
-  explicit Comparer(T value) : rhs(value) {}
+  explicit Comparer(const T &value) : rhs(&value) {}
 
   CompareResult visitArray(const CollectionData &lhs) {
     ArrayComparer comparer(lhs);
@@ -183,7 +183,7 @@ struct Comparer<T, typename enable_if<IsVisitable<T>::value>::type>
  private:
   template <typename TComparer>
   CompareResult accept(TComparer &comparer) {
-    CompareResult reversedResult = rhs.accept(comparer);
+    CompareResult reversedResult = rhs->accept(comparer);
     switch (reversedResult) {
       case COMPARE_RESULT_GREATER:
         return COMPARE_RESULT_LESS;

lib/ArduinoJson/src/ArduinoJson/version.hpp

@@ -4,7 +4,7 @@
 
 #pragma once
 
-#define ARDUINOJSON_VERSION "6.19.3"
+#define ARDUINOJSON_VERSION "6.19.4"
 #define ARDUINOJSON_VERSION_MAJOR 6
 #define ARDUINOJSON_VERSION_MINOR 19
-#define ARDUINOJSON_VERSION_REVISION 3
+#define ARDUINOJSON_VERSION_REVISION 4