From c4d487b6cfa5f25ba56d91717a6dcdfd34eca3f4 Mon Sep 17 00:00:00 2001
From: Benoit Blanchon <git@benoitblanchon.fr>
Date: Thu, 31 Mar 2022 11:59:00 +0200
Subject: [PATCH] Add getMemberConst() and getElementConst() (6780,5602)

---
 extras/tests/JsonVariant/subscript.cpp    |  3 +-
 src/ArduinoJson/Array/ArrayRef.hpp        |  9 ++++-
 src/ArduinoJson/Array/ElementProxy.hpp    | 32 ++++++++++++++--
 src/ArduinoJson/Document/JsonDocument.hpp | 26 ++++++-------
 src/ArduinoJson/Object/MemberProxy.hpp    | 38 +++++++++++++++++--
 src/ArduinoJson/Object/ObjectImpl.hpp     |  4 +-
 src/ArduinoJson/Object/ObjectRef.hpp      | 45 ++++++++++++++---------
 src/ArduinoJson/Variant/Converter.hpp     |  3 ++
 src/ArduinoJson/Variant/VariantImpl.hpp   | 29 +++++++++++----
 src/ArduinoJson/Variant/VariantRef.hpp    | 34 ++++++++++++-----
 10 files changed, 164 insertions(+), 59 deletions(-)

diff --git a/extras/tests/JsonVariant/subscript.cpp b/extras/tests/JsonVariant/subscript.cpp
index a1bba08c..a6172e63 100644
--- a/extras/tests/JsonVariant/subscript.cpp
+++ b/extras/tests/JsonVariant/subscript.cpp
@@ -154,7 +154,8 @@ TEST_CASE("JsonVariant::operator[]") {
     doc2.add(42);
     var.link(doc2);
 
-    CHECK(var[0].as<int>() == 42);
+    bool ok = var[0].as<int>() == 42;
+    CHECK(ok);
   }
 
   SECTION("set value to linked array") {
diff --git a/src/ArduinoJson/Array/ArrayRef.hpp b/src/ArduinoJson/Array/ArrayRef.hpp
index 99b4e22b..8ec2cf8f 100644
--- a/src/ArduinoJson/Array/ArrayRef.hpp
+++ b/src/ArduinoJson/Array/ArrayRef.hpp
@@ -87,10 +87,10 @@ class ArrayConstRef : public ArrayRefBase<const CollectionData>,
   }
 
   FORCE_INLINE VariantConstRef operator[](size_t index) const {
-    return getElement(index);
+    return getElementConst(index);
   }
 
-  FORCE_INLINE VariantConstRef getElement(size_t index) const {
+  FORCE_INLINE VariantConstRef getElementConst(size_t index) const {
     return VariantConstRef(_data ? _data->getElement(index) : 0);
   }
 };
@@ -151,6 +151,11 @@ class ArrayRef : public ArrayRefBase<CollectionData>,
     return VariantRef(_pool, _data ? _data->getElement(index) : 0);
   }
 
+  // Gets the value at the specified index.
+  FORCE_INLINE VariantConstRef getElementConst(size_t index) const {
+    return VariantConstRef(_data ? _data->getElement(index) : 0);
+  }
+
   // Removes element at specified position.
   FORCE_INLINE void remove(iterator it) const {
     if (!_data)
diff --git a/src/ArduinoJson/Array/ElementProxy.hpp b/src/ArduinoJson/Array/ElementProxy.hpp
index 07566551..33e73786 100644
--- a/src/ArduinoJson/Array/ElementProxy.hpp
+++ b/src/ArduinoJson/Array/ElementProxy.hpp
@@ -65,8 +65,16 @@ class ElementProxy : public VariantOperators<ElementProxy<TArray> >,
   }
 
   template <typename T>
-  FORCE_INLINE typename enable_if<!is_same<T, char*>::value, T>::type as()
-      const {
+  FORCE_INLINE typename enable_if<!is_same<T, char*>::value &&
+                                      !ConverterNeedsWriteableRef<T>::value,
+                                  T>::type
+  as() const {
+    return getUpstreamElementConst().template as<T>();
+  }
+
+  template <typename T>
+  FORCE_INLINE typename enable_if<ConverterNeedsWriteableRef<T>::value, T>::type
+  as() const {
     return getUpstreamElement().template as<T>();
   }
 
@@ -115,7 +123,7 @@ class ElementProxy : public VariantOperators<ElementProxy<TArray> >,
 
   template <typename TVisitor>
   typename TVisitor::result_type accept(TVisitor& visitor) const {
-    return getUpstreamElement().accept(visitor);
+    return getUpstreamElementConst().accept(visitor);
   }
 
   FORCE_INLINE size_t size() const {
@@ -136,6 +144,16 @@ class ElementProxy : public VariantOperators<ElementProxy<TArray> >,
     return getUpstreamElement().getMember(key);
   }
 
+  template <typename TNestedKey>
+  VariantConstRef getMemberConst(TNestedKey* key) const {
+    return getUpstreamElementConst().getMemberConst(key);
+  }
+
+  template <typename TNestedKey>
+  VariantConstRef getMemberConst(const TNestedKey& key) const {
+    return getUpstreamElementConst().getMemberConst(key);
+  }
+
   template <typename TNestedKey>
   VariantRef getOrAddMember(TNestedKey* key) const {
     return getOrAddUpstreamElement().getOrAddMember(key);
@@ -154,6 +172,10 @@ class ElementProxy : public VariantOperators<ElementProxy<TArray> >,
     return getOrAddUpstreamElement().getElement(index);
   }
 
+  VariantConstRef getElementConst(size_t index) const {
+    return getUpstreamElementConst().getElementConst(index);
+  }
+
   VariantRef getOrAddElement(size_t index) const {
     return getOrAddUpstreamElement().getOrAddElement(index);
   }
@@ -182,6 +204,10 @@ class ElementProxy : public VariantOperators<ElementProxy<TArray> >,
     return _array.getElement(_index);
   }
 
+  FORCE_INLINE VariantConstRef getUpstreamElementConst() const {
+    return _array.getElementConst(_index);
+  }
+
   FORCE_INLINE VariantRef getOrAddUpstreamElement() const {
     return _array.getOrAddElement(_index);
   }
diff --git a/src/ArduinoJson/Document/JsonDocument.hpp b/src/ArduinoJson/Document/JsonDocument.hpp
index 62d53030..9f0892a3 100644
--- a/src/ArduinoJson/Document/JsonDocument.hpp
+++ b/src/ArduinoJson/Document/JsonDocument.hpp
@@ -140,14 +140,14 @@ class JsonDocument : public Visitable,
   // containsKey(const __FlashStringHelper*) const
   template <typename TChar>
   bool containsKey(TChar* key) const {
-    return !getMember(key).isUnbound();
+    return !getMemberConst(key).isUnbound();
   }
 
   // containsKey(const std::string&) const
   // containsKey(const String&) const
   template <typename TString>
   bool containsKey(const TString& key) const {
-    return !getMember(key).isUnbound();
+    return !getMemberConst(key).isUnbound();
   }
 
   // operator[](const std::string&)
@@ -175,7 +175,7 @@ class JsonDocument : public Visitable,
   FORCE_INLINE
       typename enable_if<IsString<TString>::value, VariantConstRef>::type
       operator[](const TString& key) const {
-    return getMember(key);
+    return getMemberConst(key);
   }
 
   // operator[](char*) const
@@ -185,7 +185,7 @@ class JsonDocument : public Visitable,
   FORCE_INLINE
       typename enable_if<IsString<TChar*>::value, VariantConstRef>::type
       operator[](TChar* key) const {
-    return getMember(key);
+    return getMemberConst(key);
   }
 
   FORCE_INLINE ElementProxy<JsonDocument&> operator[](size_t index) {
@@ -193,14 +193,14 @@ class JsonDocument : public Visitable,
   }
 
   FORCE_INLINE VariantConstRef operator[](size_t index) const {
-    return getElement(index);
+    return getElementConst(index);
   }
 
   FORCE_INLINE VariantRef getElement(size_t index) {
     return VariantRef(&_pool, _data.getElement(index));
   }
 
-  FORCE_INLINE VariantConstRef getElement(size_t index) const {
+  FORCE_INLINE VariantConstRef getElementConst(size_t index) const {
     return VariantConstRef(_data.getElement(index));
   }
 
@@ -208,20 +208,20 @@ class JsonDocument : public Visitable,
     return VariantRef(&_pool, _data.getOrAddElement(index, &_pool));
   }
 
-  // JsonVariantConst getMember(char*) const
-  // JsonVariantConst getMember(const char*) const
-  // JsonVariantConst getMember(const __FlashStringHelper*) const
+  // JsonVariantConst getMemberConst(char*) const
+  // JsonVariantConst getMemberConst(const char*) const
+  // JsonVariantConst getMemberConst(const __FlashStringHelper*) const
   template <typename TChar>
-  FORCE_INLINE VariantConstRef getMember(TChar* key) const {
+  FORCE_INLINE VariantConstRef getMemberConst(TChar* key) const {
     return VariantConstRef(_data.getMember(adaptString(key)));
   }
 
-  // JsonVariantConst getMember(const std::string&) const
-  // JsonVariantConst getMember(const String&) const
+  // JsonVariantConst getMemberConst(const std::string&) const
+  // JsonVariantConst getMemberConst(const String&) const
   template <typename TString>
   FORCE_INLINE
       typename enable_if<IsString<TString>::value, VariantConstRef>::type
-      getMember(const TString& key) const {
+      getMemberConst(const TString& key) const {
     return VariantConstRef(_data.getMember(adaptString(key)));
   }
 
diff --git a/src/ArduinoJson/Object/MemberProxy.hpp b/src/ArduinoJson/Object/MemberProxy.hpp
index 8275c186..4419c3a0 100644
--- a/src/ArduinoJson/Object/MemberProxy.hpp
+++ b/src/ArduinoJson/Object/MemberProxy.hpp
@@ -6,6 +6,7 @@
 
 #include <ArduinoJson/Configuration.hpp>
 #include <ArduinoJson/Polyfills/type_traits.hpp>
+#include <ArduinoJson/Variant/Converter.hpp>
 #include <ArduinoJson/Variant/VariantOperators.hpp>
 #include <ArduinoJson/Variant/VariantRef.hpp>
 #include <ArduinoJson/Variant/VariantShortcuts.hpp>
@@ -68,8 +69,16 @@ class MemberProxy : public VariantOperators<MemberProxy<TObject, TStringRef> >,
   }
 
   template <typename T>
-  FORCE_INLINE typename enable_if<!is_same<T, char *>::value, T>::type as()
-      const {
+  FORCE_INLINE typename enable_if<!is_same<T, char *>::value &&
+                                      !ConverterNeedsWriteableRef<T>::value,
+                                  T>::type
+  as() const {
+    return getUpstreamMemberConst().template as<T>();
+  }
+
+  template <typename T>
+  FORCE_INLINE typename enable_if<ConverterNeedsWriteableRef<T>::value, T>::type
+  as() const {
     return getUpstreamMember().template as<T>();
   }
 
@@ -141,7 +150,7 @@ class MemberProxy : public VariantOperators<MemberProxy<TObject, TStringRef> >,
 
   template <typename TVisitor>
   typename TVisitor::result_type accept(TVisitor &visitor) const {
-    return getUpstreamMember().accept(visitor);
+    return getUpstreamMemberConst().accept(visitor);
   }
 
   FORCE_INLINE VariantRef addElement() const {
@@ -152,6 +161,10 @@ class MemberProxy : public VariantOperators<MemberProxy<TObject, TStringRef> >,
     return getUpstreamMember().getElement(index);
   }
 
+  FORCE_INLINE VariantConstRef getElementConst(size_t index) const {
+    return getUpstreamMemberConst().getElementConst(index);
+  }
+
   FORCE_INLINE VariantRef getOrAddElement(size_t index) const {
     return getOrAddUpstreamMember().getOrAddElement(index);
   }
@@ -171,6 +184,21 @@ class MemberProxy : public VariantOperators<MemberProxy<TObject, TStringRef> >,
     return getUpstreamMember().getMember(key);
   }
 
+  // getMemberConst(char*) const
+  // getMemberConst(const char*) const
+  // getMemberConst(const __FlashStringHelper*) const
+  template <typename TChar>
+  FORCE_INLINE VariantConstRef getMemberConst(TChar *key) const {
+    return getUpstreamMember().getMemberConst(key);
+  }
+
+  // getMemberConst(const std::string&) const
+  // getMemberConst(const String&) const
+  template <typename TString>
+  FORCE_INLINE VariantConstRef getMemberConst(const TString &key) const {
+    return getUpstreamMember().getMemberConst(key);
+  }
+
   // getOrAddMember(char*) const
   // getOrAddMember(const char*) const
   // getOrAddMember(const __FlashStringHelper*) const
@@ -191,6 +219,10 @@ class MemberProxy : public VariantOperators<MemberProxy<TObject, TStringRef> >,
     return _object.getMember(_key);
   }
 
+  FORCE_INLINE VariantConstRef getUpstreamMemberConst() const {
+    return _object.getMemberConst(_key);
+  }
+
   FORCE_INLINE VariantRef getOrAddUpstreamMember() const {
     return _object.getOrAddMember(_key);
   }
diff --git a/src/ArduinoJson/Object/ObjectImpl.hpp b/src/ArduinoJson/Object/ObjectImpl.hpp
index 66793a77..ba327628 100644
--- a/src/ArduinoJson/Object/ObjectImpl.hpp
+++ b/src/ArduinoJson/Object/ObjectImpl.hpp
@@ -40,14 +40,14 @@ template <typename TObject>
 template <typename TString>
 inline typename enable_if<IsString<TString>::value, bool>::type
 ObjectShortcuts<TObject>::containsKey(const TString& key) const {
-  return !impl()->getMember(key).isUnbound();
+  return !impl()->getMemberConst(key).isUnbound();
 }
 
 template <typename TObject>
 template <typename TChar>
 inline typename enable_if<IsString<TChar*>::value, bool>::type
 ObjectShortcuts<TObject>::containsKey(TChar* key) const {
-  return !impl()->getMember(key).isUnbound();
+  return !impl()->getMemberConst(key).isUnbound();
 }
 
 template <typename TObject>
diff --git a/src/ArduinoJson/Object/ObjectRef.hpp b/src/ArduinoJson/Object/ObjectRef.hpp
index 2d11bfbb..a278f016 100644
--- a/src/ArduinoJson/Object/ObjectRef.hpp
+++ b/src/ArduinoJson/Object/ObjectRef.hpp
@@ -81,7 +81,7 @@ class ObjectConstRef : public ObjectRefBase<const CollectionData>,
   // containsKey(const String&) const
   template <typename TString>
   FORCE_INLINE bool containsKey(const TString& key) const {
-    return !getMember(key).isUnbound();
+    return !getMemberConst(key).isUnbound();
   }
 
   // containsKey(char*) const
@@ -89,22 +89,22 @@ class ObjectConstRef : public ObjectRefBase<const CollectionData>,
   // containsKey(const __FlashStringHelper*) const
   template <typename TChar>
   FORCE_INLINE bool containsKey(TChar* key) const {
-    return !getMember(key).isUnbound();
+    return !getMemberConst(key).isUnbound();
   }
 
-  // getMember(const std::string&) const
-  // getMember(const String&) const
+  // getMemberConst(const std::string&) const
+  // getMemberConst(const String&) const
   template <typename TString>
-  FORCE_INLINE VariantConstRef getMember(const TString& key) const {
-    return get_impl(adaptString(key));
+  FORCE_INLINE VariantConstRef getMemberConst(const TString& key) const {
+    return VariantConstRef(objectGetMember(_data, adaptString(key)));
   }
 
-  // getMember(char*) const
-  // getMember(const char*) const
-  // getMember(const __FlashStringHelper*) const
+  // getMemberConst(char*) const
+  // getMemberConst(const char*) const
+  // getMemberConst(const __FlashStringHelper*) const
   template <typename TChar>
-  FORCE_INLINE VariantConstRef getMember(TChar* key) const {
-    return get_impl(adaptString(key));
+  FORCE_INLINE VariantConstRef getMemberConst(TChar* key) const {
+    return VariantConstRef(objectGetMember(_data, adaptString(key)));
   }
 
   // operator[](const std::string&) const
@@ -113,7 +113,7 @@ class ObjectConstRef : public ObjectRefBase<const CollectionData>,
   FORCE_INLINE
       typename enable_if<IsString<TString>::value, VariantConstRef>::type
       operator[](const TString& key) const {
-    return get_impl(adaptString(key));
+    return getMemberConst(key);
   }
 
   // operator[](char*) const
@@ -123,7 +123,7 @@ class ObjectConstRef : public ObjectRefBase<const CollectionData>,
   FORCE_INLINE
       typename enable_if<IsString<TChar*>::value, VariantConstRef>::type
       operator[](TChar* key) const {
-    return get_impl(adaptString(key));
+    return getMemberConst(key);
   }
 
   FORCE_INLINE bool operator==(ObjectConstRef rhs) const {
@@ -131,10 +131,6 @@ class ObjectConstRef : public ObjectRefBase<const CollectionData>,
   }
 
  private:
-  template <typename TAdaptedString>
-  FORCE_INLINE VariantConstRef get_impl(TAdaptedString key) const {
-    return VariantConstRef(objectGetMember(_data, key));
-  }
 };
 
 class ObjectRef : public ObjectRefBase<CollectionData>,
@@ -195,6 +191,21 @@ class ObjectRef : public ObjectRefBase<CollectionData>,
     return VariantRef(_pool, objectGetMember(_data, adaptString(key)));
   }
 
+  // getMemberConst(const std::string&) const
+  // getMemberConst(const String&) const
+  template <typename TString>
+  FORCE_INLINE VariantConstRef getMemberConst(const TString& key) const {
+    return VariantConstRef(objectGetMember(_data, adaptString(key)));
+  }
+
+  // getMemberConst(char*) const
+  // getMemberConst(const char*) const
+  // getMemberConst(const __FlashStringHelper*) const
+  template <typename TChar>
+  FORCE_INLINE VariantConstRef getMemberConst(TChar* key) const {
+    return VariantConstRef(objectGetMember(_data, adaptString(key)));
+  }
+
   // getOrAddMember(const std::string&) const
   // getOrAddMember(const String&) const
   template <typename TString>
diff --git a/src/ArduinoJson/Variant/Converter.hpp b/src/ArduinoJson/Variant/Converter.hpp
index f9ce9ab7..72f9dfd4 100644
--- a/src/ArduinoJson/Variant/Converter.hpp
+++ b/src/ArduinoJson/Variant/Converter.hpp
@@ -14,4 +14,7 @@ template <typename T1, typename T2>
 class InvalidConversion;  // Error here? See https://arduinojson.org/v6/invalid-conversion/
 // clang-format on
 
+template <typename T>
+struct ConverterNeedsWriteableRef;
+
 }  // namespace ARDUINOJSON_NAMESPACE
diff --git a/src/ArduinoJson/Variant/VariantImpl.hpp b/src/ArduinoJson/Variant/VariantImpl.hpp
index 9be59a74..31a5db34 100644
--- a/src/ArduinoJson/Variant/VariantImpl.hpp
+++ b/src/ArduinoJson/Variant/VariantImpl.hpp
@@ -124,7 +124,7 @@ VariantRef::to() const {
   return *this;
 }
 
-inline VariantConstRef VariantConstRef::getElement(size_t index) const {
+inline VariantConstRef VariantConstRef::getElementConst(size_t index) const {
   return ArrayConstRef(_data != 0 ? _data->resolve()->asArray() : 0)[index];
 }
 
@@ -133,8 +133,11 @@ inline VariantRef VariantRef::addElement() const {
 }
 
 inline VariantRef VariantRef::getElement(size_t index) const {
-  return VariantRef(_pool,
-                    _data != 0 ? _data->resolve()->getElement(index) : 0);
+  return VariantRef(_pool, _data != 0 ? _data->getElement(index) : 0);
+}
+
+inline VariantConstRef VariantRef::getElementConst(size_t index) const {
+  return VariantConstRef(_data != 0 ? _data->resolve()->getElement(index) : 0);
 }
 
 inline VariantRef VariantRef::getOrAddElement(size_t index) const {
@@ -143,16 +146,26 @@ inline VariantRef VariantRef::getOrAddElement(size_t index) const {
 
 template <typename TChar>
 inline VariantRef VariantRef::getMember(TChar *key) const {
-  return VariantRef(  // TODO: this returns a mutable reference to a linked
-                      // object
-      _pool, _data != 0 ? _data->resolve()->getMember(adaptString(key)) : 0);
+  return VariantRef(_pool, _data != 0 ? _data->getMember(adaptString(key)) : 0);
 }
 
 template <typename TString>
 inline typename enable_if<IsString<TString>::value, VariantRef>::type
 VariantRef::getMember(const TString &key) const {
-  return VariantRef(  // TODO: idem
-      _pool, _data != 0 ? _data->resolve()->getMember(adaptString(key)) : 0);
+  return VariantRef(_pool, _data != 0 ? _data->getMember(adaptString(key)) : 0);
+}
+
+template <typename TChar>
+inline VariantConstRef VariantRef::getMemberConst(TChar *key) const {
+  return VariantConstRef(
+      _data != 0 ? _data->resolve()->getMember(adaptString(key)) : 0);
+}
+
+template <typename TString>
+inline typename enable_if<IsString<TString>::value, VariantConstRef>::type
+VariantRef::getMemberConst(const TString &key) const {
+  return VariantConstRef(
+      _data != 0 ? _data->resolve()->getMember(adaptString(key)) : 0);
 }
 
 template <typename TChar>
diff --git a/src/ArduinoJson/Variant/VariantRef.hpp b/src/ArduinoJson/Variant/VariantRef.hpp
index bfed6134..bb6a0d12 100644
--- a/src/ArduinoJson/Variant/VariantRef.hpp
+++ b/src/ArduinoJson/Variant/VariantRef.hpp
@@ -174,6 +174,8 @@ class VariantRef : public VariantRefBase<VariantData>,
 
   FORCE_INLINE VariantRef getElement(size_t) const;
 
+  FORCE_INLINE class VariantConstRef getElementConst(size_t) const;
+
   FORCE_INLINE VariantRef getOrAddElement(size_t) const;
 
   // getMember(const char*) const
@@ -187,6 +189,18 @@ class VariantRef : public VariantRefBase<VariantData>,
   FORCE_INLINE typename enable_if<IsString<TString>::value, VariantRef>::type
   getMember(const TString &) const;
 
+  // getMemberConst(const char*) const
+  // getMemberConst(const __FlashStringHelper*) const
+  template <typename TChar>
+  FORCE_INLINE class VariantConstRef getMemberConst(TChar *) const;
+
+  // getMemberConst(const std::string&) const
+  // getMemberConst(const String&) const
+  template <typename TString>
+  FORCE_INLINE
+      typename enable_if<IsString<TString>::value, class VariantConstRef>::type
+      getMemberConst(const TString &) const;
+
   // getOrAddMember(char*) const
   // getOrAddMember(const char*) const
   // getOrAddMember(const __FlashStringHelper*) const
@@ -293,25 +307,25 @@ class VariantConstRef : public VariantRefBase<const VariantData>,
     return as<T>();
   }
 
-  FORCE_INLINE VariantConstRef getElement(size_t) const;
+  FORCE_INLINE VariantConstRef getElementConst(size_t) const;
 
   FORCE_INLINE VariantConstRef operator[](size_t index) const {
-    return getElement(index);
+    return getElementConst(index);
   }
 
-  // getMember(const std::string&) const
-  // getMember(const String&) const
+  // getMemberConst(const std::string&) const
+  // getMemberConst(const String&) const
   template <typename TString>
-  FORCE_INLINE VariantConstRef getMember(const TString &key) const {
+  FORCE_INLINE VariantConstRef getMemberConst(const TString &key) const {
     return VariantConstRef(
         objectGetMember(variantAsObject(_data), adaptString(key)));
   }
 
-  // getMember(char*) const
-  // getMember(const char*) const
-  // getMember(const __FlashStringHelper*) const
+  // getMemberConst(char*) const
+  // getMemberConst(const char*) const
+  // getMemberConst(const __FlashStringHelper*) const
   template <typename TChar>
-  FORCE_INLINE VariantConstRef getMember(TChar *key) const {
+  FORCE_INLINE VariantConstRef getMemberConst(TChar *key) const {
     const CollectionData *obj = variantAsObject(_data);
     return VariantConstRef(obj ? obj->getMember(adaptString(key)) : 0);
   }
@@ -332,7 +346,7 @@ class VariantConstRef : public VariantRefBase<const VariantData>,
   FORCE_INLINE
       typename enable_if<IsString<TChar *>::value, VariantConstRef>::type
       operator[](TChar *key) const {
-    return getMember(key);
+    return getMemberConst(key);
   }
 };