Fix lookups of properties in QML singletons

An unqualified name that points to a QML singleton will evaluate to a
QQmlTypeWrapper JS object. A member lookup in such an object is not
guaranteed to always produce the same property. The property cache check
may protect us from that, but we must still retrieve the QObject
singleton for every lookup.

Task-number: QTBUG-75896
Change-Id: Ibd9bac6e5c2047f838758811790b299ace636446
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>
 

6 files changed, 46 insertions, 11 deletions

diff --git a/src/qml/jsruntime/qv4lookup_p.h b/src/qml/jsruntime/qv4lookup_p.h
index 03dc5f6d3c..4fd5e133f7 100644
--- a/src/qml/jsruntime/qv4lookup_p.h
+++ b/src/qml/jsruntime/qv4lookup_p.h
@@ -120,7 +120,7 @@ struct Lookup {
         } indexedLookup;
         struct {
             Heap::InternalClass *ic;
-            Heap::QObjectWrapper *staticQObject;
+            Heap::InternalClass *qmlTypeIc; // only used when lookup goes through QQmlTypeWrapper
             QQmlPropertyCache *propertyCache;
             QQmlPropertyData *propertyData;
         } qobjectLookup;
diff --git a/src/qml/jsruntime/qv4qmlcontext.cpp b/src/qml/jsruntime/qv4qmlcontext.cpp
index 0c5226d46c..6aa0130188 100644
--- a/src/qml/jsruntime/qv4qmlcontext.cpp
+++ b/src/qml/jsruntime/qv4qmlcontext.cpp
@@ -293,7 +293,6 @@ ReturnedValue QQmlContextWrapper::getPropertyAndBase(const QQmlContextWrapper *r
                         ScopedValue val(scope, base ? *base : Value::fromReturnedValue(QV4::QObjectWrapper::wrap(v4, scopeObject)));
                         const QObjectWrapper *That = static_cast<const QObjectWrapper *>(val->objectValue());
                         lookup->qobjectLookup.ic = That->internalClass();
-                        lookup->qobjectLookup.staticQObject = nullptr;
                         lookup->qobjectLookup.propertyCache = ddata->propertyCache;
                         lookup->qobjectLookup.propertyCache->addref();
                         lookup->qobjectLookup.propertyData = propertyData;
@@ -326,7 +325,6 @@ ReturnedValue QQmlContextWrapper::getPropertyAndBase(const QQmlContextWrapper *r
                             ScopedValue val(scope, base ? *base : Value::fromReturnedValue(QV4::QObjectWrapper::wrap(v4, context->contextObject)));
                             const QObjectWrapper *That = static_cast<const QObjectWrapper *>(val->objectValue());
                             lookup->qobjectLookup.ic = That->internalClass();
-                            lookup->qobjectLookup.staticQObject = nullptr;
                             lookup->qobjectLookup.propertyCache = ddata->propertyCache;
                             lookup->qobjectLookup.propertyCache->addref();
                             lookup->qobjectLookup.propertyData = propertyData;
diff --git a/src/qml/jsruntime/qv4qobjectwrapper.cpp b/src/qml/jsruntime/qv4qobjectwrapper.cpp
index 6fed538fa8..63b6435112 100644
--- a/src/qml/jsruntime/qv4qobjectwrapper.cpp
+++ b/src/qml/jsruntime/qv4qobjectwrapper.cpp
@@ -870,7 +870,6 @@ ReturnedValue QObjectWrapper::virtualResolveLookupGetter(const Object *object, E
     }
 
     lookup->qobjectLookup.ic = This->internalClass();
-    lookup->qobjectLookup.staticQObject = nullptr;
     lookup->qobjectLookup.propertyCache = ddata->propertyCache;
     lookup->qobjectLookup.propertyCache->addref();
     lookup->qobjectLookup.propertyData = property;
diff --git a/src/qml/jsruntime/qv4qobjectwrapper_p.h b/src/qml/jsruntime/qv4qobjectwrapper_p.h
index 2558ede401..5543c4d5a6 100644
--- a/src/qml/jsruntime/qv4qobjectwrapper_p.h
+++ b/src/qml/jsruntime/qv4qobjectwrapper_p.h
@@ -233,8 +233,7 @@ inline ReturnedValue QObjectWrapper::lookupGetterImpl(Lookup *lookup, ExecutionE
     if (!o || o->internalClass != lookup->qobjectLookup.ic)
         return revertLookup();
 
-    const Heap::QObjectWrapper *This = lookup->qobjectLookup.staticQObject ? lookup->qobjectLookup.staticQObject :
-                                                                             static_cast<const Heap::QObjectWrapper *>(o);
+    const Heap::QObjectWrapper *This = static_cast<const Heap::QObjectWrapper *>(o);
     QObject *qobj = This->object();
     if (QQmlData::wasDeleted(qobj))
         return QV4::Encode::undefined();
diff --git a/src/qml/qml/qqmltypewrapper.cpp b/src/qml/qml/qqmltypewrapper.cpp
index 24c5aecc00..c5fa4a04ec 100644
--- a/src/qml/qml/qqmltypewrapper.cpp
+++ b/src/qml/qml/qqmltypewrapper.cpp
@@ -459,16 +459,16 @@ ReturnedValue QQmlTypeWrapper::virtualResolveLookupGetter(const Object *object,
                 if (!includeEnums || !name->startsWithUpper()) {
                     QQmlData *ddata = QQmlData::get(qobjectSingleton, false);
                     if (ddata && ddata->propertyCache) {
-                        ScopedValue val(scope, Value::fromReturnedValue(QV4::QObjectWrapper::wrap(engine, qobjectSingleton)));
                         QQmlPropertyData *property = ddata->propertyCache->property(name.getPointer(), qobjectSingleton, qmlContext);
                         if (property) {
-                            lookup->qobjectLookup.ic = This->internalClass();
-                            lookup->qobjectLookup.staticQObject = static_cast<Heap::QObjectWrapper *>(val->heapObject());
+                            ScopedValue val(scope, Value::fromReturnedValue(QV4::QObjectWrapper::wrap(engine, qobjectSingleton)));
+                            lookup->qobjectLookup.qmlTypeIc = This->internalClass();
+                            lookup->qobjectLookup.ic = val->objectValue()->internalClass();
                             lookup->qobjectLookup.propertyCache = ddata->propertyCache;
                             lookup->qobjectLookup.propertyCache->addref();
                             lookup->qobjectLookup.propertyData = property;
-                            lookup->getter = QV4::QObjectWrapper::lookupGetter;
-                            return lookup->getter(lookup, engine, *This);
+                            lookup->getter = QQmlTypeWrapper::lookupSingletonProperty;
+                            return lookup->getter(lookup, engine, *object);
                         }
                         // Fall through to base implementation
                     }
@@ -488,6 +488,43 @@ bool QQmlTypeWrapper::virtualResolveLookupSetter(Object *object, ExecutionEngine
     return Object::virtualResolveLookupSetter(object, engine, lookup, value);
 }
 
+ReturnedValue QQmlTypeWrapper::lookupSingletonProperty(Lookup *l, ExecutionEngine *engine, const Value &object)
+{
+    const auto revertLookup = [l, engine, &object]() {
+        l->qobjectLookup.propertyCache->release();
+        l->qobjectLookup.propertyCache = nullptr;
+        l->getter = Lookup::getterGeneric;
+        return Lookup::getterGeneric(l, engine, object);
+    };
+
+    // we can safely cast to a QV4::Object here. If object is something else,
+    // the internal class won't match
+    Heap::Object *o = static_cast<Heap::Object *>(object.heapObject());
+    if (!o || o->internalClass != l->qobjectLookup.qmlTypeIc)
+        return revertLookup();
+
+    Heap::QQmlTypeWrapper *This = static_cast<Heap::QQmlTypeWrapper *>(o);
+
+    QQmlType type = This->type();
+    if (!type.isValid())
+        return revertLookup();
+
+    if (!type.isSingleton())
+        return revertLookup();
+
+    QQmlEngine *e = engine->qmlEngine();
+    QQmlType::SingletonInstanceInfo *siinfo = type.singletonInstanceInfo();
+    siinfo->init(e);
+
+    QObject *qobjectSingleton = siinfo->qobjectApi(e);
+    if (!qobjectSingleton)
+        return revertLookup();
+
+    Scope scope(engine);
+    ScopedValue obj(scope, QV4::QObjectWrapper::wrap(engine, qobjectSingleton));
+    return QObjectWrapper::lookupGetterImpl(l, engine, obj, /*useOriginalProperty*/ true, revertLookup);
+}
+
 void Heap::QQmlScopedEnumWrapper::destroy()
 {
     QQmlType::derefHandle(typePrivate);
diff --git a/src/qml/qml/qqmltypewrapper_p.h b/src/qml/qml/qqmltypewrapper_p.h
index 44e82dec2b..5f3cb2523f 100644
--- a/src/qml/qml/qqmltypewrapper_p.h
+++ b/src/qml/qml/qqmltypewrapper_p.h
@@ -114,6 +114,8 @@ struct Q_QML_EXPORT QQmlTypeWrapper : Object
     static ReturnedValue virtualResolveLookupGetter(const Object *object, ExecutionEngine *engine, Lookup *lookup);
     static bool virtualResolveLookupSetter(Object *object, ExecutionEngine *engine, Lookup *lookup, const Value &value);
 
+    static ReturnedValue lookupSingletonProperty(Lookup *l, ExecutionEngine *engine, const Value &base);
+
 protected:
     static ReturnedValue virtualGet(const Managed *m, PropertyKey id, const Value *receiver, bool *hasProperty);
     static bool virtualPut(Managed *m, PropertyKey id, const Value &value, Value *receiver);