QmlDesigner: Allow invalid property value for QVariant type properties

Invalid QVariant is a valid value for properties of type QVariant, so
propagate the value change from puppet to creator in that case.

Also change the property editor to notify controls of value change in
case of invalid value set, and clear LineEdit when invalid value is
set.

Fixes: QDS-5304
Change-Id: I02c7daaf3cde06317690a32e7ac8a82da754bd58
Reviewed-by: Mahmoud Badri <mahmoud.badri@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Thomas Hartmann <thomas.hartmann@qt.io>

share/qtcreator/qml/qmlpuppet/qml2puppet/instances/nodeinstanceserver.cpp

@@ -1221,7 +1221,15 @@ ValuesChangedCommand NodeInstanceServer::createValuesChangedCommand(const QVecto
 
         if (instance.isValid()) {
             QVariant propertyValue = instance.property(propertyName);
-            if (QMetaType::isRegistered(propertyValue.userType()) && supportedVariantType(propertyValue.type())) {
+            bool isValid = QMetaType::isRegistered(propertyValue.userType())
+                    && supportedVariantType(propertyValue.type());
+            if (!isValid && propertyValue.userType() == 0) {
+                // If the property is QVariant type, invalid variant can be a valid value
+                const QMetaObject *mo = instance.internalObject()->metaObject();
+                const int idx = mo->indexOfProperty(propertyName);
+                isValid = idx >= 0 && mo->property(idx).userType() == QMetaType::QVariant;
+            }
+            if (isValid) {
                 valueVector.append(PropertyValueContainer(instance.instanceId(), propertyName,
                                                           propertyValue, PropertyName()));
             }

share/qtcreator/qmldesigner/propertyEditorQmlSources/imports/HelperWidgets/LineEdit.qml

@@ -76,13 +76,13 @@ StudioControls.TextField {
         id: colorLogic
         backendValue: lineEdit.backendValue
         onValueFromBackendChanged: {
-            if (colorLogic.valueFromBackend === undefined)
+            if (colorLogic.valueFromBackend === undefined) {
-                return
+                lineEdit.text = ""
-
-            if (writeValueManually) {
-                lineEdit.text = convertColorToString(colorLogic.valueFromBackend)
             } else {
-                lineEdit.text = colorLogic.valueFromBackend
+                if (writeValueManually)
+                    lineEdit.text = convertColorToString(colorLogic.valueFromBackend)
+                else
+                    lineEdit.text = colorLogic.valueFromBackend
             }
             __dirty = false
         }

src/plugins/qmldesigner/components/propertyeditor/propertyeditorvalue.cpp

@@ -167,7 +167,7 @@ void PropertyEditorValue::setValue(const QVariant &value)
     fixAmbigousColorNames(modelNode(), name(), &m_value);
     fixUrl(modelNode(), name(), &m_value);
 
-    if (m_value.isValid() && !colorsEqual)
+    if (!colorsEqual)
         emit valueChangedQml();
 
     emit isExplicitChanged();