4 files changed, 110 insertions, 0 deletions

diff --git a/src/core/nodes/qentity.cpp b/src/core/nodes/qentity.cpp
index 64ea65087..2ef78deb6 100644
--- a/src/core/nodes/qentity.cpp
+++ b/src/core/nodes/qentity.cpp
@@ -152,6 +152,8 @@ void QEntity::addComponent(QComponent *comp)
     if (!comp->parent())
         comp->setParent(this);
 
+    QNodePrivate::get(comp)->_q_ensureBackendNodeCreated();
+
     d->m_components.append(comp);
 
     // Ensures proper bookkeeping
diff --git a/src/core/nodes/qnode.cpp b/src/core/nodes/qnode.cpp
index 8143ccc75..c2373b805 100644
--- a/src/core/nodes/qnode.cpp
+++ b/src/core/nodes/qnode.cpp
@@ -506,6 +506,29 @@ void QNodePrivate::setArbiter(QLockableObserverInterface *arbiter)
 }
 
 /*!
+ * \internal
+ * Makes sure this node has a backend by traversing the tree up to the most distant ancestor
+ * without a backend node and initializing that node. This is done to make sure the parent nodes
+ * are always created before the child nodes, since child nodes reference parent nodes at creation
+ * time.
+ */
+void QNodePrivate::_q_ensureBackendNodeCreated()
+{
+    if (m_hasBackendNode)
+        return;
+
+    Q_Q(QNode);
+
+    QNode *nextNode = q;
+    QNode *topNodeWithoutBackend = nullptr;
+    while (nextNode != nullptr && !QNodePrivate::get(nextNode)->m_hasBackendNode) {
+        topNodeWithoutBackend = nextNode;
+        nextNode = nextNode->parentNode();
+    }
+    QNodePrivate::get(topNodeWithoutBackend)->_q_postConstructorInit();
+}
+
+/*!
     \class Qt3DCore::QNode
     \inherits QObject
 
diff --git a/src/core/nodes/qnode_p.h b/src/core/nodes/qnode_p.h
index 73893cc1e..6ffb19ce8 100644
--- a/src/core/nodes/qnode_p.h
+++ b/src/core/nodes/qnode_p.h
@@ -152,6 +152,7 @@ public:
     static const QMetaObject *findStaticMetaObject(const QMetaObject *metaObject);
 
     void _q_postConstructorInit();
+    void _q_ensureBackendNodeCreated();
 
 private:
     void notifyCreationChange();
diff --git a/tests/auto/core/nodes/tst_nodes.cpp b/tests/auto/core/nodes/tst_nodes.cpp
index 0106d2dc3..3f7fb4a75 100644
--- a/tests/auto/core/nodes/tst_nodes.cpp
+++ b/tests/auto/core/nodes/tst_nodes.cpp
@@ -89,6 +89,7 @@ private slots:
     void appendingComponentToEntity();
     void appendingParentlessComponentToEntityWithoutScene();
     void appendingParentlessComponentToEntityWithScene();
+    void appendingParentlessComponentToNonRootEntity();
     void removingComponentFromEntity();
 
     void changeCustomProperty();
@@ -1322,6 +1323,89 @@ void tst_Nodes::appendingParentlessComponentToEntityWithoutScene()
     }
 }
 
+void tst_Nodes::appendingParentlessComponentToNonRootEntity()
+{
+    // GIVEN
+    ObserverSpy eventSpy;
+    Qt3DCore::QScene scene;
+
+    {
+        QScopedPointer<MyQEntity> root(new MyQEntity());
+        root->setArbiterAndScene(&eventSpy, &scene);
+        root->setSimulateBackendCreated(true);
+
+        QCoreApplication::processEvents();
+
+        QScopedPointer<MyQEntity> entity(new MyQEntity(root.data()));
+        MyQComponent *comp = new MyQComponent();
+
+        // THEN
+        QVERIFY(root->parentNode() == nullptr);
+        QVERIFY(root->children().count() == 1);
+        QVERIFY(root->components().empty());
+        QVERIFY(entity->parentNode() == root.data());
+        QVERIFY(entity->children().count() == 0);
+        QVERIFY(entity->components().empty());
+        QVERIFY(comp->parentNode() == nullptr);
+
+        // WHEN
+        entity->addComponent(comp);
+        QCoreApplication::processEvents();
+
+        // THEN
+        QVERIFY(entity->components().count() == 1);
+        QVERIFY(entity->components().first() == comp);
+        QVERIFY(comp->parentNode() == entity.data());
+
+        QCOMPARE(eventSpy.events.size(), 5);
+        // - entity created
+        // - comp created
+        // - entity added as child to root
+        // - component added for entity
+        // - component added for compontent
+        QVERIFY(eventSpy.events.first().wasLocked());
+
+        {
+            const auto event = eventSpy.events.takeFirst().change().dynamicCast<Qt3DCore::QNodeCreatedChangeBase>();
+            QVERIFY(!event.isNull());
+            QCOMPARE(event->type(), Qt3DCore::NodeCreated);
+            QCOMPARE(event->subjectId(), entity->id());
+        }
+        {
+            const auto event = eventSpy.events.takeFirst().change().dynamicCast<Qt3DCore::QNodeCreatedChangeBase>();
+            QVERIFY(!event.isNull());
+            QCOMPARE(event->type(), Qt3DCore::NodeCreated);
+            QCOMPARE(event->subjectId(), comp->id());
+        }
+        {
+            const auto event = eventSpy.events.takeFirst().change().dynamicCast<Qt3DCore::QPropertyNodeAddedChange>();
+            QVERIFY(!event.isNull());
+            QCOMPARE(event->type(), Qt3DCore::PropertyValueAdded);
+            QCOMPARE(event->subjectId(), root->id());
+            QCOMPARE(event->propertyName(), QByteArrayLiteral("children"));
+            QCOMPARE(event->addedNodeId(), entity->id());
+        }
+        {
+            const auto event = eventSpy.events.takeFirst().change().dynamicCast<Qt3DCore::QComponentAddedChange>();
+            QVERIFY(!event.isNull());
+            QCOMPARE(event->type(), Qt3DCore::ComponentAdded);
+            QCOMPARE(event->subjectId(), entity->id());
+            QCOMPARE(event->entityId(), entity->id());
+            QCOMPARE(event->componentId(), comp->id());
+            QCOMPARE(event->componentMetaObject(), comp->metaObject());
+        }
+        {
+            const auto event = eventSpy.events.takeFirst().change().dynamicCast<Qt3DCore::QComponentAddedChange>();
+            QVERIFY(!event.isNull());
+            QCOMPARE(event->type(), Qt3DCore::ComponentAdded);
+            QCOMPARE(event->subjectId(), comp->id());
+            QCOMPARE(event->entityId(), entity->id());
+            QCOMPARE(event->componentId(), comp->id());
+            QCOMPARE(event->componentMetaObject(), comp->metaObject());
+        }
+    }
+}
+
 void tst_Nodes::appendingParentlessComponentToEntityWithScene()
 {
     // GIVEN