Use std::optional instead of bool to indicate success of de/encoding

QOpcUaGenericStructHandler is a new class in Qt 6.7, and has two
functions that return values but might fail. The modern C++ way of
doing this is to return a std::optional, rather than return a bool with
the value returned through an out-parameter (or a default-
constructed value with a boolean out-parameter to indicate success).

Found during API review.

Pick-to: 6.7
Change-Id: Ib2ba6098f53eccab73beace6844028d0b674ca65
Reviewed-by: Ivan Solovev <ivan.solovev@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>

4 files changed, 140 insertions, 146 deletions

diff --git a/examples/opcua/opcuaviewer/treeitem.cpp b/examples/opcua/opcuaviewer/treeitem.cpp
index c8ced61..1cbbc02 100644
--- a/examples/opcua/opcuaviewer/treeitem.cpp
+++ b/examples/opcua/opcuaviewer/treeitem.cpp
@@ -343,10 +343,9 @@ QString TreeItem::variantToString(const QVariant &value, const QString &typeNode
         if (mModel->genericStructHandler() &&
             mModel->genericStructHandler()->dataTypeKindForTypeId(mModel->genericStructHandler()->typeIdForBinaryEncodingId(obj.encodingTypeId()))
                                                   == QOpcUaGenericStructHandler::DataTypeKind::Struct) {
-            bool decodeSuccess = false;
-            const auto decodedValue = mModel->genericStructHandler()->decode(obj, decodeSuccess);
-            if (decodeSuccess)
-                return decodedValue.toString();
+            const auto decodedValue = mModel->genericStructHandler()->decode(obj);
+            if (decodedValue)
+                return decodedValue->toString();
         }
 
         return u"[TypeId: \"%1\", Encoding: %2, Body: 0x%3]"_s.arg(obj.encodingTypeId(),
diff --git a/src/opcua/client/qopcuagenericstructhandler.cpp b/src/opcua/client/qopcuagenericstructhandler.cpp
index 42b79ba..3cf0af8 100644
--- a/src/opcua/client/qopcuagenericstructhandler.cpp
+++ b/src/opcua/client/qopcuagenericstructhandler.cpp
@@ -56,13 +56,12 @@ QT_BEGIN_NAMESPACE
             auto extObj = node->valueAttribute().value<QOpcUaExtensionObject>();
             qDebug() << "Got object of type" << handler.typeNameForBinaryEncodingId(extObj.encodingTypeId());
 
-            bool success = false;
-            auto result = handler.decode(extObj, success);
+            const auto result = handler.decode(extObj);
 
-            if (!success)
+            if (!result)
                 return;
 
-            qDebug() << result;
+            qDebug() << *result;
         });
     });
     \endcode
@@ -81,10 +80,9 @@ QT_BEGIN_NAMESPACE
         value.fieldsRef()["MandatoryMember"] = 23.0;
         value.fieldsRef()["OptionalMember"] = 42.0;
 
-        QOpcUaExtensionObject ext;
-        bool success = handler.encode(value, ext);
+        const auto ext = handler.encode(value);
 
-        if (!success)
+        if (!ext)
             return;
 
         // Use the extension object to write a node's value attribute, in a method parameter, etc...
@@ -136,20 +134,26 @@ bool QOpcUaGenericStructHandler::initialize()
 }
 
 /*!
-    Decodes \a extensionObject to a \l QOpcUaGenericStructValue. If the decoder fails, a default constructed value is returned.
-    \a success indicates if the decoding was successful after the method has returned.
+    Decodes \a extensionObject to a \l QOpcUaGenericStructValue. If the decoder fails, \c std::nullopt is returned.
 */
-QOpcUaGenericStructValue QOpcUaGenericStructHandler::decode(const QOpcUaExtensionObject &extensionObject, bool &success) const
+std::optional<QOpcUaGenericStructValue> QOpcUaGenericStructHandler::decode(const QOpcUaExtensionObject &extensionObject) const
 {
-    return d_func()->decode(extensionObject, success);
+    bool success = false;
+    auto result = d_func()->decode(extensionObject, success);
+    if (!success)
+        return std::nullopt;
+    return result;
 }
 
 /*!
-    Encodes \a value into the extension object \a output. Returns \c true if the value was successfully encoded.
+    Returns \a value encoded as a \l QOpcUaExtensionObject, or \c std::nullopt if the value could not be encoded.
  */
-bool QOpcUaGenericStructHandler::encode(const QOpcUaGenericStructValue &value, QOpcUaExtensionObject &output)
+std::optional<QOpcUaExtensionObject> QOpcUaGenericStructHandler::encode(const QOpcUaGenericStructValue &value)
 {
-    return d_func()->encode(value, output);
+    QOpcUaExtensionObject output;
+    if (!d_func()->encode(value, output))
+        return std::nullopt;
+    return output;
 }
 
 /*!
diff --git a/src/opcua/client/qopcuagenericstructhandler.h b/src/opcua/client/qopcuagenericstructhandler.h
index 16c0ac1..de8b47b 100644
--- a/src/opcua/client/qopcuagenericstructhandler.h
+++ b/src/opcua/client/qopcuagenericstructhandler.h
@@ -9,6 +9,8 @@
 
 #include <QtCore/qobject.h>
 
+#include <optional>
+
 #ifndef QOPCUAGENERICSTRUCTHANDLER_H
 #define QOPCUAGENERICSTRUCTHANDLER_H
 
@@ -25,8 +27,8 @@ public:
 
     bool initialize();
 
-    QOpcUaGenericStructValue decode(const QOpcUaExtensionObject &extensionObject, bool &success) const;
-    bool encode(const QOpcUaGenericStructValue &value, QOpcUaExtensionObject &output);
+    std::optional<QOpcUaGenericStructValue> decode(const QOpcUaExtensionObject &extensionObject) const;
+    std::optional<QOpcUaExtensionObject> encode(const QOpcUaGenericStructValue &value);
 
     QOpcUaGenericStructValue createGenericStructValueForTypeId(const QString &typeId);
 
diff --git a/tests/auto/qopcuaclient/tst_client.cpp b/tests/auto/qopcuaclient/tst_client.cpp
index c025f68..7fd6a30 100644
--- a/tests/auto/qopcuaclient/tst_client.cpp
+++ b/tests/auto/qopcuaclient/tst_client.cpp
@@ -6041,35 +6041,33 @@ void Tst_QOpcUaClient::decodeGenericStruct()
     QCOMPARE(results.at(5).statusCode(), QOpcUa::UaStatusCode::Good);
     QCOMPARE(results.at(6).statusCode(), QOpcUa::UaStatusCode::Good);
 
-    bool decodeSuccess = false;
-
     {
         auto nestedStructExt = results.at(0).value().value<QOpcUaExtensionObject>();
-        auto decodedData = decoder.decode(nestedStructExt, decodeSuccess);
-        QCOMPARE(decodeSuccess, true);
-        qDebug() << decodedData;
+        auto decodedData = decoder.decode(nestedStructExt);
+        QVERIFY(decodedData);
+        qDebug() << *decodedData;
 
-        QCOMPARE(decodedData.typeName(), "QtTestStructType");
+        QCOMPARE(decodedData->typeName(), "QtTestStructType");
 
-        QCOMPARE(decodedData.fields().value("EnumMember").toInt(), 1);
-        QCOMPARE(decodedData.fields().value("Int64ArrayMember").value<QList<qint64>>(),
+        QCOMPARE(decodedData->fields().value("EnumMember").toInt(), 1);
+        QCOMPARE(decodedData->fields().value("Int64ArrayMember").value<QList<qint64>>(),
                  QList<qint64>({std::numeric_limits<qint64>::max(),
                                 std::numeric_limits<qint64>::max() - 1,
                                 std::numeric_limits<qint64>::min()}));
 
-        QCOMPARE(decodedData.fields().value("LocalizedTextMember").value<QOpcUaLocalizedText>().locale(), "en");
-        QCOMPARE(decodedData.fields().value("LocalizedTextMember").value<QOpcUaLocalizedText>().text(), "TestText");
+        QCOMPARE(decodedData->fields().value("LocalizedTextMember").value<QOpcUaLocalizedText>().locale(), "en");
+        QCOMPARE(decodedData->fields().value("LocalizedTextMember").value<QOpcUaLocalizedText>().text(), "TestText");
 
-        QCOMPARE(decodedData.fields().value("QualifiedNameMember").value<QOpcUaQualifiedName>().namespaceIndex(), 1);
-        QCOMPARE(decodedData.fields().value("QualifiedNameMember").value<QOpcUaQualifiedName>().name(), "TestName");
+        QCOMPARE(decodedData->fields().value("QualifiedNameMember").value<QOpcUaQualifiedName>().namespaceIndex(), 1);
+        QCOMPARE(decodedData->fields().value("QualifiedNameMember").value<QOpcUaQualifiedName>().name(), "TestName");
 
-        QCOMPARE(decodedData.fields().value("StringMember").value<QString>(), "TestString");
+        QCOMPARE(decodedData->fields().value("StringMember").value<QString>(), "TestString");
 
-        auto nestedStructValue = decodedData.fields().value("NestedStructMember").value<QOpcUaGenericStructValue>();
+        auto nestedStructValue = decodedData->fields().value("NestedStructMember").value<QOpcUaGenericStructValue>();
         QCOMPARE(nestedStructValue.typeName(), "QtInnerTestStructType");
         QCOMPARE(nestedStructValue.fields().value("DoubleSubtypeMember").toDouble(), 42.0);
 
-        auto nestedStructArrayValue = decodedData.fields().value("NestedStructArrayMember").value<QList<QOpcUaGenericStructValue>>();
+        auto nestedStructArrayValue = decodedData->fields().value("NestedStructArrayMember").value<QList<QOpcUaGenericStructValue>>();
         QCOMPARE(nestedStructArrayValue.size(), 2);
         QCOMPARE(nestedStructArrayValue.at(0).typeName(), "QtInnerTestStructType");
         QCOMPARE(nestedStructArrayValue.at(0).fields().value("DoubleSubtypeMember").toDouble(), 23.0);
@@ -6079,71 +6077,71 @@ void Tst_QOpcUaClient::decodeGenericStruct()
 
     {
         auto unionExt = results.at(1).value().value<QOpcUaExtensionObject>();
-        auto decodedData = decoder.decode(unionExt, decodeSuccess);
-        QCOMPARE(decodeSuccess, true);
-        qDebug() << decodedData;
+        auto decodedData = decoder.decode(unionExt);
+        QVERIFY(decodedData);
+        qDebug() << *decodedData;
 
-        QCOMPARE(decodedData.typeName(), "QtTestUnionType");
-        QCOMPARE(decodedData.fields().value("Member1"), 42);
+        QCOMPARE(decodedData->typeName(), "QtTestUnionType");
+        QCOMPARE(decodedData->fields().value("Member1"), 42);
     }
 
     {
         auto unionExt = results.at(2).value().value<QOpcUaExtensionObject>();
-        auto decodedData = decoder.decode(unionExt, decodeSuccess);
-        QCOMPARE(decodeSuccess, true);
-        qDebug() << decodedData;
+        auto decodedData = decoder.decode(unionExt);
+        QVERIFY(decodedData);
+        qDebug() << *decodedData;
 
-        QCOMPARE(decodedData.typeName(), "QtTestUnionType");
+        QCOMPARE(decodedData->typeName(), "QtTestUnionType");
 
-        auto unionFieldValue = decodedData.fields().value("Member2").value<QOpcUaGenericStructValue>();
+        auto unionFieldValue = decodedData->fields().value("Member2").value<QOpcUaGenericStructValue>();
         QCOMPARE(unionFieldValue.fields().value("DoubleSubtypeMember").toDouble(), 23.0);
     }
 
     // Struct type with optional field with optional field set
     {
         auto optionalFieldExt = results.at(3).value().value<QOpcUaExtensionObject>();
-        auto decodedData = decoder.decode(optionalFieldExt, decodeSuccess);
-        QCOMPARE(decodeSuccess, true);
-        qDebug() << decodedData;
+        auto decodedData = decoder.decode(optionalFieldExt);
+        QVERIFY(decodedData);
+        qDebug() << *decodedData;
 
-        QCOMPARE(decodedData.typeName(), "QtStructWithOptionalFieldType");
+        QCOMPARE(decodedData->typeName(), "QtStructWithOptionalFieldType");
 
-        QCOMPARE(decodedData.fields().value("MandatoryMember").toDouble(), 42.0);
-        QCOMPARE(decodedData.fields().value("OptionalMember").toDouble(), 23.0);
+        QCOMPARE(decodedData->fields().value("MandatoryMember").toDouble(), 42.0);
+        QCOMPARE(decodedData->fields().value("OptionalMember").toDouble(), 23.0);
     }
 
     // Struct type with optional field without optional field set
     {
         auto optionalFieldExt = results.at(4).value().value<QOpcUaExtensionObject>();
-        auto decodedData = decoder.decode(optionalFieldExt, decodeSuccess);
-        QCOMPARE(decodeSuccess, true);
-        qDebug() << decodedData;
+        auto decodedData = decoder.decode(optionalFieldExt);
+        QVERIFY(decodedData);
+        qDebug() << *decodedData;
 
-        QCOMPARE(decodedData.typeName(), "QtStructWithOptionalFieldType");
+        QCOMPARE(decodedData->typeName(), "QtStructWithOptionalFieldType");
 
-        QCOMPARE(decodedData.fields().value("MandatoryMember").toDouble(), 42.0);
-        QCOMPARE(decodedData.fields().contains("OptionalMember"), false);
+        QCOMPARE(decodedData->fields().value("MandatoryMember").toDouble(), 42.0);
+        QCOMPARE(decodedData->fields().contains("OptionalMember"), false);
     }
 
     {
         auto diagnosticInfoExt = results.at(5).value().value<QOpcUaExtensionObject>();
-        auto decodedData = decoder.decode(diagnosticInfoExt, decodeSuccess);
-        qDebug() << decodedData;
-        QCOMPARE(decodedData.fields().contains("DiagnosticInfoMember"), true);
-        QCOMPARE(decodedData.fields().value("DiagnosticInfoMember").value<QOpcUaDiagnosticInfo>(), testDiagnosticInfos.at(0));
-        QCOMPARE(decodedData.fields().contains("DiagnosticInfoArrayMember"), true);
-        QCOMPARE(decodedData.fields().value("DiagnosticInfoArrayMember").value<QList<QOpcUaDiagnosticInfo>>(), testDiagnosticInfos);
-        QCOMPARE(decodeSuccess, true);
+        auto decodedData = decoder.decode(diagnosticInfoExt);
+        QVERIFY(decodedData);
+        qDebug() << *decodedData;
+        QCOMPARE(decodedData->fields().contains("DiagnosticInfoMember"), true);
+        QCOMPARE(decodedData->fields().value("DiagnosticInfoMember").value<QOpcUaDiagnosticInfo>(), testDiagnosticInfos.at(0));
+        QCOMPARE(decodedData->fields().contains("DiagnosticInfoArrayMember"), true);
+        QCOMPARE(decodedData->fields().value("DiagnosticInfoArrayMember").value<QList<QOpcUaDiagnosticInfo>>(), testDiagnosticInfos);
     }
 
     {
         auto dataValueExt = results.at(6).value().value<QOpcUaExtensionObject>();
-        auto decodedData = decoder.decode(dataValueExt, decodeSuccess);
-        qDebug() << decodedData;
-        QCOMPARE(decodeSuccess, true);
+        auto decodedData = decoder.decode(dataValueExt);
+        QVERIFY(decodedData);
+        qDebug() << *decodedData;
 
-        QVERIFY(decodedData.fields().contains("DataValueMember"));
-        const auto dv = decodedData.fields().value("DataValueMember").value<QOpcUaDataValue>();
+        QVERIFY(decodedData->fields().contains("DataValueMember"));
+        const auto dv = decodedData->fields().value("DataValueMember").value<QOpcUaDataValue>();
         QCOMPARE(dv.statusCode(), QOpcUa::UaStatusCode::BadInternalError);
         QCOMPARE(dv.serverTimestamp(), QDateTime::fromMSecsSinceEpoch(1698655307000));
         QCOMPARE(dv.sourceTimestamp(), QDateTime::fromMSecsSinceEpoch(1698655306000));
@@ -6153,8 +6151,8 @@ void Tst_QOpcUaClient::decodeGenericStruct()
         QCOMPARE(v.value(), (QList<QString>{"TestString 1", "TestString 2", "TestString 3", "TestString 4"}));
         QCOMPARE(v.arrayDimensions(), (QList<qint32>{ 2, 2 }));
 
-        QVERIFY(decodedData.fields().contains("VariantMember"));
-        const auto var = decodedData.fields().value("VariantMember").value<QOpcUaVariant>();
+        QVERIFY(decodedData->fields().contains("VariantMember"));
+        const auto var = decodedData->fields().value("VariantMember").value<QOpcUaVariant>();
         QVERIFY(var.arrayDimensions().isEmpty());
         QCOMPARE(var.type(), QOpcUaVariant::ValueType::UInt64);
         QCOMPARE(var.value(), 42);
@@ -6200,22 +6198,22 @@ void Tst_QOpcUaClient::encodeGenericStruct()
         value.fieldsRef()["NestedStructArrayMember"] =
             QVariant::fromValue(QList<QOpcUaGenericStructValue>({innerValue1, innerValue2}));
 
-        QOpcUaExtensionObject ext;
-        success = handler.encode(value, ext);
-        QCOMPARE(success, true);
+        auto ext = handler.encode(value);
+        QVERIFY(ext);
 
-        const auto decoded = handler.decode(ext, success);
+        const auto decoded = handler.decode(*ext);
+        QVERIFY(decoded);
 
-        QCOMPARE(decoded.fields().value("StringMember"), "StringMember");
-        QCOMPARE(decoded.fields().value("LocalizedTextMember"), QOpcUaLocalizedText("en", "Localized text"));
-        QCOMPARE(decoded.fields().value("QualifiedNameMember"), QOpcUaQualifiedName(1, "Qualified name"));
-        QCOMPARE(decoded.fields().value("Int64ArrayMember"), QVariant::fromValue(QList<qint64>({1, 2, 3, 4})));
-        QCOMPARE(decoded.fields().value("EnumMember"), 42);
+        QCOMPARE(decoded->fields().value("StringMember"), "StringMember");
+        QCOMPARE(decoded->fields().value("LocalizedTextMember"), QOpcUaLocalizedText("en", "Localized text"));
+        QCOMPARE(decoded->fields().value("QualifiedNameMember"), QOpcUaQualifiedName(1, "Qualified name"));
+        QCOMPARE(decoded->fields().value("Int64ArrayMember"), QVariant::fromValue(QList<qint64>({1, 2, 3, 4})));
+        QCOMPARE(decoded->fields().value("EnumMember"), 42);
 
-        const auto innerDecoded = decoded.fields().value("NestedStructMember").value<QOpcUaGenericStructValue>();
+        const auto innerDecoded = decoded->fields().value("NestedStructMember").value<QOpcUaGenericStructValue>();
         QCOMPARE(innerDecoded.fields().value("DoubleSubtypeMember"), 42.0);
 
-        auto nestedStructArrayValue = decoded.fields().value("NestedStructArrayMember").value<QList<QOpcUaGenericStructValue>>();
+        auto nestedStructArrayValue = decoded->fields().value("NestedStructArrayMember").value<QList<QOpcUaGenericStructValue>>();
         QCOMPARE(nestedStructArrayValue.size(), 2);
         QCOMPARE(nestedStructArrayValue.at(0).typeName(), "QtInnerTestStructType");
         QCOMPARE(nestedStructArrayValue.at(0).fields().value("DoubleSubtypeMember").toDouble(), 23.0);
@@ -6223,25 +6221,24 @@ void Tst_QOpcUaClient::encodeGenericStruct()
         QCOMPARE(nestedStructArrayValue.at(1).fields().value("DoubleSubtypeMember").toDouble(), 42.0);
 
         QScopedPointer<QOpcUaNode> node(opcuaClient->node("ns=4;i=6009"));
-        WRITE_VALUE_ATTRIBUTE(node, ext, QOpcUa::Types::ExtensionObject);
+        WRITE_VALUE_ATTRIBUTE(node, *ext, QOpcUa::Types::ExtensionObject);
     }
 
     {
         auto unionValue = handler.createGenericStructValueForTypeId("ns=4;i=3005");
         unionValue.fieldsRef()["Member1"] = 23;
 
-        QOpcUaExtensionObject ext;
-        success = handler.encode(unionValue, ext);
-        QCOMPARE(success, true);
-        QCOMPARE(ext.encodingTypeId(), unionValue.structureDefinition().defaultEncodingId());
+        auto ext = handler.encode(unionValue);
+        QVERIFY(ext);
+        QCOMPARE(ext->encodingTypeId(), unionValue.structureDefinition().defaultEncodingId());
 
-        const auto decoded = handler.decode(ext, success);
-        QCOMPARE(success, true);
+        const auto decoded = handler.decode(*ext);
+        QVERIFY(decoded);
 
-        QCOMPARE(decoded.fields().value("Member1"), 23);
+        QCOMPARE(decoded->fields().value("Member1"), 23);
 
         QScopedPointer<QOpcUaNode> node(opcuaClient->node("ns=4;i=6011"));
-        WRITE_VALUE_ATTRIBUTE(node, ext, QOpcUa::Types::ExtensionObject);
+        WRITE_VALUE_ATTRIBUTE(node, *ext, QOpcUa::Types::ExtensionObject);
     }
 
     {
@@ -6250,22 +6247,20 @@ void Tst_QOpcUaClient::encodeGenericStruct()
         innerValue.fieldsRef()["DoubleSubtypeMember"] = 42.0;
         unionValue.fieldsRef()["Member2"] = innerValue;
 
-        QOpcUaExtensionObject ext;
-        success = handler.encode(unionValue, ext);
-        QCOMPARE(success, true);
-        QCOMPARE(ext.encodingTypeId(), unionValue.structureDefinition().defaultEncodingId());
-
-        const auto decoded = handler.decode(ext, success);
-        QCOMPARE(success, true);
+        auto ext = handler.encode(unionValue);
+        QVERIFY(ext);
+        QCOMPARE(ext->encodingTypeId(), unionValue.structureDefinition().defaultEncodingId());
 
+        const auto decoded = handler.decode(*ext);
+        QVERIFY(decoded);
 
-        QVERIFY(decoded.fields().contains("Member2"));
+        QVERIFY(decoded->fields().contains("Member2"));
 
-        const auto innerDecoded = decoded.fields().value("Member2").value<QOpcUaGenericStructValue>();
+        const auto innerDecoded = decoded->fields().value("Member2").value<QOpcUaGenericStructValue>();
         QCOMPARE(innerDecoded.fields().value("DoubleSubtypeMember"), 42.0);
 
         QScopedPointer<QOpcUaNode> node(opcuaClient->node("ns=4;i=6003"));
-        WRITE_VALUE_ATTRIBUTE(node, ext, QOpcUa::Types::ExtensionObject);
+        WRITE_VALUE_ATTRIBUTE(node, *ext, QOpcUa::Types::ExtensionObject);
     }
 
     {
@@ -6273,36 +6268,34 @@ void Tst_QOpcUaClient::encodeGenericStruct()
         value.fieldsRef()["MandatoryMember"] = 23.0;
         value.fieldsRef()["OptionalMember"] = 42.0;
 
-        QOpcUaExtensionObject ext;
-        success = handler.encode(value, ext);
-        QCOMPARE(success, true);
-        QCOMPARE(ext.encodingTypeId(), value.structureDefinition().defaultEncodingId());
+        auto ext = handler.encode(value);
+        QVERIFY(ext);
+        QCOMPARE(ext->encodingTypeId(), value.structureDefinition().defaultEncodingId());
 
-        const auto decoded = handler.decode(ext, success);
+        const auto decoded = handler.decode(*ext);
 
-        QCOMPARE(decoded.fields().value("MandatoryMember"), 23.0);
-        QCOMPARE(decoded.fields().value("OptionalMember"), 42.0);
+        QCOMPARE(decoded->fields().value("MandatoryMember"), 23.0);
+        QCOMPARE(decoded->fields().value("OptionalMember"), 42.0);
 
         QScopedPointer<QOpcUaNode> node(opcuaClient->node("ns=4;i=6010"));
-        WRITE_VALUE_ATTRIBUTE(node, ext, QOpcUa::Types::ExtensionObject);
+        WRITE_VALUE_ATTRIBUTE(node, *ext, QOpcUa::Types::ExtensionObject);
     }
 
     {
         auto value = handler.createGenericStructValueForTypeId("ns=4;i=3006");
         value.fieldsRef()["MandatoryMember"] = 23.0;
 
-        QOpcUaExtensionObject ext;
-        success = handler.encode(value, ext);
-        QCOMPARE(success, true);
-        QCOMPARE(ext.encodingTypeId(), value.structureDefinition().defaultEncodingId());
+        auto ext = handler.encode(value);
+        QVERIFY(ext);
+        QCOMPARE(ext->encodingTypeId(), value.structureDefinition().defaultEncodingId());
 
-        const auto decoded = handler.decode(ext, success);
+        const auto decoded = handler.decode(*ext);
 
-        QCOMPARE(decoded.fields().value("MandatoryMember"), 23.0);
-        QCOMPARE(decoded.fields().contains("OptionalMember"), false);
+        QCOMPARE(decoded->fields().value("MandatoryMember"), 23.0);
+        QCOMPARE(decoded->fields().contains("OptionalMember"), false);
 
         QScopedPointer<QOpcUaNode> node(opcuaClient->node("ns=4;i=6002"));
-        WRITE_VALUE_ATTRIBUTE(node, ext, QOpcUa::Types::ExtensionObject);
+        WRITE_VALUE_ATTRIBUTE(node, *ext, QOpcUa::Types::ExtensionObject);
     }
 
     {
@@ -6310,17 +6303,16 @@ void Tst_QOpcUaClient::encodeGenericStruct()
         value.fieldsRef()["DiagnosticInfoMember"] = testDiagnosticInfos.at(0);
         value.fieldsRef()["DiagnosticInfoArrayMember"] = QVariant::fromValue(testDiagnosticInfos);
 
-        QOpcUaExtensionObject ext;
-        success = handler.encode(value, ext);
-        QCOMPARE(success, true);
-        QCOMPARE(ext.encodingTypeId(), value.structureDefinition().defaultEncodingId());
+        auto ext = handler.encode(value);
+        QVERIFY(ext);
+        QCOMPARE(ext->encodingTypeId(), value.structureDefinition().defaultEncodingId());
 
-        const auto decoded = handler.decode(ext, success);
-        QCOMPARE(decoded.fields().value("DiagnosticInfoMember"), testDiagnosticInfos.at(0));
-        QCOMPARE(decoded.fields().value("DiagnosticInfoArrayMember").value<QList<QOpcUaDiagnosticInfo>>(), testDiagnosticInfos);
+        const auto decoded = handler.decode(*ext);
+        QCOMPARE(decoded->fields().value("DiagnosticInfoMember"), testDiagnosticInfos.at(0));
+        QCOMPARE(decoded->fields().value("DiagnosticInfoArrayMember").value<QList<QOpcUaDiagnosticInfo>>(), testDiagnosticInfos);
 
         QScopedPointer<QOpcUaNode> node(opcuaClient->node("ns=4;i=6006"));
-        WRITE_VALUE_ATTRIBUTE(node, ext, QOpcUa::Types::ExtensionObject);
+        WRITE_VALUE_ATTRIBUTE(node, *ext, QOpcUa::Types::ExtensionObject);
     }
 
     {
@@ -6328,18 +6320,17 @@ void Tst_QOpcUaClient::encodeGenericStruct()
         value.fieldsRef()["DataValueMember"] = testDataValues.at(0);
         value.fieldsRef()["VariantMember"] = testVariants.at(0);
 
-        QOpcUaExtensionObject ext;
-        success = handler.encode(value, ext);
-        QCOMPARE(success, true);
-        QCOMPARE(ext.encodingTypeId(), value.structureDefinition().defaultEncodingId());
+        auto ext = handler.encode(value);
+        QVERIFY(ext);
+        QCOMPARE(ext->encodingTypeId(), value.structureDefinition().defaultEncodingId());
 
-        const auto decoded = handler.decode(ext, success);
+        const auto decoded = handler.decode(*ext);
 
-        QCOMPARE(decoded.fields().value("DataValueMember"), testDataValues.at(0));
-        QCOMPARE(decoded.fields().value("VariantMember"), testVariants.at(0));
+        QCOMPARE(decoded->fields().value("DataValueMember"), testDataValues.at(0));
+        QCOMPARE(decoded->fields().value("VariantMember"), testVariants.at(0));
 
         QScopedPointer<QOpcUaNode> node(opcuaClient->node("ns=4;i=6027"));
-        WRITE_VALUE_ATTRIBUTE(node, ext, QOpcUa::Types::ExtensionObject);
+        WRITE_VALUE_ATTRIBUTE(node, *ext, QOpcUa::Types::ExtensionObject);
     }
 }
 
@@ -6381,15 +6372,14 @@ void Tst_QOpcUaClient::encodeCustomGenericStruct()
         auto value = handler.createGenericStructValueForTypeId("ns=5;i=23");
         value.fieldsRef()["MatrixMember"] = QOpcUaMultiDimensionalArray({1, 2, 3, 4}, {2, 2});
 
-        QOpcUaExtensionObject ext;
-        success = handler.encode(value, ext);
-        QVERIFY(success);
-        QCOMPARE(ext.encodingTypeId(), value.structureDefinition().defaultEncodingId());
+        auto ext = handler.encode(value);
+        QVERIFY(ext);
+        QCOMPARE(ext->encodingTypeId(), value.structureDefinition().defaultEncodingId());
 
-        const auto decoded = handler.decode(ext, success);
+        const auto decoded = handler.decode(*ext);
         QVERIFY(success);
 
-        const auto matrix = decoded.fields().value("MatrixMember").value<QOpcUaMultiDimensionalArray>();
+        const auto matrix = decoded->fields().value("MatrixMember").value<QOpcUaMultiDimensionalArray>();
         QCOMPARE(matrix.arrayDimensions(), QList<quint32>({2, 2}));
         QCOMPARE(matrix.value(QList<quint32>({0, 0})), 1);
         QCOMPARE(matrix.value(QList<quint32>({0, 1})), 2);
@@ -6429,15 +6419,14 @@ void Tst_QOpcUaClient::encodeCustomGenericStruct()
         value.fieldsRef()["StructMatrixMember"] =
             QOpcUaMultiDimensionalArray(QVariantList({innerValue1, innerValue2, innerValue3, innerValue4}), {2, 2});
 
-        QOpcUaExtensionObject ext;
-        success = handler.encode(value, ext);
-        QVERIFY(success);
-        QCOMPARE(ext.encodingTypeId(), value.structureDefinition().defaultEncodingId());
+        auto ext = handler.encode(value);
+        QVERIFY(ext);
+        QCOMPARE(ext->encodingTypeId(), value.structureDefinition().defaultEncodingId());
 
-        const auto decoded = handler.decode(ext, success);
-        QVERIFY(success);
+        const auto decoded = handler.decode(*ext);
+        QVERIFY(decoded);
 
-        const auto matrix = decoded.fields().value("StructMatrixMember").value<QOpcUaMultiDimensionalArray>();
+        const auto matrix = decoded->fields().value("StructMatrixMember").value<QOpcUaMultiDimensionalArray>();
         QCOMPARE(matrix.arrayDimensions(), QList<quint32>({2, 2}));
         QCOMPARE(matrix.value(QList<quint32>({0, 0})).value<QOpcUaGenericStructValue>().fields().value("DoubleSubtypeMember"), 1);
         QCOMPARE(matrix.value(QList<quint32>({0, 1})).value<QOpcUaGenericStructValue>().fields().value("DoubleSubtypeMember"), 2);