Add initial support for deep aliases

This patch reuses the existing support for value types to support
aliases of depth 2. This covers the initial use case in QTBUG-48150.

Adding support for "deeper" aliases would require storing the complete
"property path", which in turn would require increasing the size of the
Alias data. This is currently considered out of scope, at least until a
clear use-case appears.

Fixes: QTBUG-48150
Change-Id: Id2ac4dd175003a37eba2919e7604d0a3be54d29f
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

1 files changed, 35 insertions, 16 deletions

diff --git a/src/qml/qml/qqmltypecompiler.cpp b/src/qml/qml/qqmltypecompiler.cpp
index bbeaf7be9a..9ff0e3fb9e 100644
--- a/src/qml/qml/qqmltypecompiler.cpp
+++ b/src/qml/qml/qqmltypecompiler.cpp
@@ -1016,7 +1016,7 @@ bool QQmlComponentAndAliasResolver::resolveAliases(int componentIndex)
             }
 
             if (result == AllAliasesResolved) {
-                QQmlJS::DiagnosticMessage error = aliasCacheCreator.appendAliasesToPropertyCache(*qmlObjects->at(componentIndex), objectIndex);
+                QQmlJS::DiagnosticMessage error = aliasCacheCreator.appendAliasesToPropertyCache(*qmlObjects->at(componentIndex), objectIndex, enginePrivate);
                 if (error.isValid()) {
                     recordError(error);
                     return false;
@@ -1143,23 +1143,42 @@ QQmlComponentAndAliasResolver::resolveAliasesInObject(int objectIndex,
             if (!subProperty.isEmpty()) {
                 const QMetaObject *valueTypeMetaObject = QQmlValueTypeFactory::metaObjectForMetaType(targetProperty->propType());
                 if (!valueTypeMetaObject) {
-                    *error = qQmlCompileError(
-                            alias->referenceLocation,
-                            tr("Invalid alias target location: %1").arg(subProperty.toString()));
-                    break;
-                }
+                    // could be a deep alias
+                    bool isDeepAlias = subProperty.at(0).isLower();
+                    if (isDeepAlias) {
+                        isDeepAlias = false;
+                        for (auto it = targetObject->bindingsBegin(); it != targetObject->bindingsEnd(); ++it) {
+                            auto binding = *it;
+                            if (compiler->stringAt(binding.propertyNameIndex) == property) {
+                                resolver = QQmlPropertyResolver(propertyCaches.at(binding.value.objectIndex));
+                                QQmlPropertyData *actualProperty = resolver.property(subProperty.toString());
+                                if (actualProperty) {
+                                    propIdx = QQmlPropertyIndex(propIdx.coreIndex(), actualProperty->coreIndex());
+                                    isDeepAlias = true;
+                                }
+                            }
+                        }
+                    }
+                    if (!isDeepAlias) {
+                        *error = qQmlCompileError(
+                                alias->referenceLocation,
+                                tr("Invalid alias target location: %1").arg(subProperty.toString()));
+                        break;
+                    }
+                } else {
 
-                int valueTypeIndex =
-                        valueTypeMetaObject->indexOfProperty(subProperty.toString().toUtf8().constData());
-                if (valueTypeIndex == -1) {
-                    *error = qQmlCompileError(
-                            alias->referenceLocation,
-                            tr("Invalid alias target location: %1").arg(subProperty.toString()));
-                    break;
-                }
-                Q_ASSERT(valueTypeIndex <= 0x0000FFFF);
+                    int valueTypeIndex =
+                            valueTypeMetaObject->indexOfProperty(subProperty.toString().toUtf8().constData());
+                    if (valueTypeIndex == -1) {
+                        *error = qQmlCompileError(
+                                alias->referenceLocation,
+                                tr("Invalid alias target location: %1").arg(subProperty.toString()));
+                        break;
+                    }
+                    Q_ASSERT(valueTypeIndex <= 0x0000FFFF);
 
-                propIdx = QQmlPropertyIndex(propIdx.coreIndex(), valueTypeIndex);
+                    propIdx = QQmlPropertyIndex(propIdx.coreIndex(), valueTypeIndex);
+                }
             } else {
                 if (targetProperty->isQObject())
                     alias->flags |= QV4::CompiledData::Alias::AliasPointsToPointerObject;