Fix error reporting in the new object creator

Propagate error conditions from createVMEMetaObjectAndPropertyCache to the caller
and properly clean up refcounts (using QQmlRefPointer)

Also fixed qmlscene to report errors if create() failed.

Change-Id: I75d984798a197c102078e5d5638ed92f167ab49f
Reviewed-by: Lars Knoll <lars.knoll@digia.com>

src/qml/qml/qqmlobjectcreator.cpp

@@ -204,20 +204,26 @@ QObject *QmlObjectCreator::create(int index, QObject *parent)
     context->addObject(_object);
 
     // ### avoid _object->metaObject
-    QQmlPropertyCache *baseTypeCache = QQmlEnginePrivate::get(engine)->cache(_object->metaObject());
-    baseTypeCache->addref();
+    QQmlRefPointer<QQmlPropertyCache> baseTypeCache = QQmlEnginePrivate::get(engine)->cache(_object->metaObject());
 
-    QQmlPropertyCache *cache = 0;
+    QQmlRefPointer<QQmlPropertyCache> cache;
     QByteArray vmeMetaData;
-    bool needCustomMetaObject = createVMEMetaObjectAndPropertyCache(obj, baseTypeCache, &cache, &vmeMetaData);
-    cache->addref();
 
-    baseTypeCache->release();
+    const bool customMO = needsCustomMetaObject(obj);
+    if (customMO) {
+        QQmlPropertyCache *newCache = 0;
+        if (!createVMEMetaObjectAndPropertyCache(obj, baseTypeCache, &newCache, &vmeMetaData))
+            return 0;
+        cache = newCache;
+    } else {
+        cache = baseTypeCache;
+    }
+
     baseTypeCache = 0;
 
     qSwap(_propertyCache, cache);
 
-    if (needCustomMetaObject) {
+    if (customMO) {
         runtimeData->datas.append(vmeMetaData);
         // install on _object
         (void)new QQmlVMEMetaObject(_object, _propertyCache, reinterpret_cast<const QQmlVMEMetaData*>(runtimeData->datas.last().constData()));
@@ -249,22 +255,22 @@ QObject *QmlObjectCreator::create(int index, QObject *parent)
     qSwap(_ddata, declarativeData);
     qSwap(_object, result);
 
-    cache->release();
-
     return result;
 }
 
+bool QmlObjectCreator::needsCustomMetaObject(const QV4::CompiledData::Object *obj)
+{
+    return obj->nProperties > 0 || obj->nSignals > 0 || obj->nFunctions > 0;
+}
+
 // ###
 #define COMPILE_EXCEPTION(token, desc) {}
 
 static QAtomicInt classIndexCounter(0);
 
-bool QmlObjectCreator::createVMEMetaObjectAndPropertyCache(const QV4::CompiledData::Object *obj, QQmlPropertyCache *baseTypeCache, QQmlPropertyCache **outputCache, QByteArray *vmeMetaObjectData) const
+bool QmlObjectCreator::createVMEMetaObjectAndPropertyCache(const QV4::CompiledData::Object *obj, QQmlPropertyCache *baseTypeCache, QQmlPropertyCache **outputCache, QByteArray *vmeMetaObjectData)
 {
-    if (!obj->nProperties) {
-        *outputCache = baseTypeCache;
-        return false;
-    }
+    Q_ASSERT(needsCustomMetaObject(obj));
 
     QQmlPropertyCache *cache = baseTypeCache->copyAndReserve(engine, obj->nProperties, /*methodCount*/0, /*signalCount*/0);
     *outputCache = cache;

src/qml/qml/qqmlobjectcreator_p.h

@@ -64,7 +64,10 @@ struct Q_QML_EXPORT QmlObjectCreator
 
     QList<QQmlError> errors;
 
-    bool createVMEMetaObjectAndPropertyCache(const QV4::CompiledData::Object *obj, QQmlPropertyCache *baseTypeCache, QQmlPropertyCache **cache, QByteArray *vmeMetaObjectData) const;
+    static bool needsCustomMetaObject(const QV4::CompiledData::Object *obj);
+    bool createVMEMetaObjectAndPropertyCache(const QV4::CompiledData::Object *obj, QQmlPropertyCache *baseTypeCache,
+                                             // out parameters
+                                             QQmlPropertyCache **cache, QByteArray *vmeMetaObjectData);
 private:
     QString stringAt(int idx) const { return unit->header.stringAt(idx); }
 
@@ -87,7 +90,7 @@ private:
 
     QObject *_object;
     QQmlData *_ddata;
-    QQmlPropertyCache *_propertyCache;
+    QQmlRefPointer<QQmlPropertyCache> _propertyCache;
 };
 
 } // end namespace QtQml

tools/qmlscene/main.cpp

@@ -483,6 +483,10 @@ int main(int argc, char ** argv)
             }
 
             QObject *topLevel = component->create();
+            if (!topLevel && component->isError()) {
+                qWarning("%s", qPrintable(component->errorString()));
+                return -1;
+            }
             QScopedPointer<QQuickWindow> window(qobject_cast<QQuickWindow *>(topLevel));
             if (window) {
                 engine.setIncubationController(window->incubationController());