Minor optimization

I've seen people write

    property SomeItem myProperty: null

This is an unnecessary initialization that ends up creating a binding
expression. Generally there's handling missing for null and undefined, but in
this very case we should just optimize away the initializer expression,
because QObject style properties are initialized to null by default, as opposed
to undefined.

Change-Id: I7af4cd45461304753c93cef3926f6e92d3b6c95d
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

4 files changed, 61 insertions, 0 deletions

diff --git a/tests/auto/qml/qqmlecmascript/data/NullObjectInitializerBase.qml b/tests/auto/qml/qqmlecmascript/data/NullObjectInitializerBase.qml
new file mode 100644
index 0000000000..4006a2a782
--- /dev/null
+++ b/tests/auto/qml/qqmlecmascript/data/NullObjectInitializerBase.qml
@@ -0,0 +1,5 @@
+import QtQml 2.0
+QtObject {
+    property Component factory: Component { QtObject {} }
+    property QtObject testProperty: factory.createObject()
+}
diff --git a/tests/auto/qml/qqmlecmascript/data/nullObjectInitializer.2.qml b/tests/auto/qml/qqmlecmascript/data/nullObjectInitializer.2.qml
new file mode 100644
index 0000000000..d59f8f99f9
--- /dev/null
+++ b/tests/auto/qml/qqmlecmascript/data/nullObjectInitializer.2.qml
@@ -0,0 +1,8 @@
+import QtQml 2.0
+NullObjectInitializerBase {
+    testProperty: null
+    property bool success: false
+    Component.onCompleted: {
+        success = testProperty === null;
+    }
+}
diff --git a/tests/auto/qml/qqmlecmascript/data/nullObjectInitializer.qml b/tests/auto/qml/qqmlecmascript/data/nullObjectInitializer.qml
new file mode 100644
index 0000000000..32bc62c9f2
--- /dev/null
+++ b/tests/auto/qml/qqmlecmascript/data/nullObjectInitializer.qml
@@ -0,0 +1,4 @@
+import QtQml 2.0
+QtObject {
+    property QtObject testProperty: null
+}
diff --git a/tests/auto/qml/qqmlecmascript/tst_qqmlecmascript.cpp b/tests/auto/qml/qqmlecmascript/tst_qqmlecmascript.cpp
index 7abbd1938d..07b5e55384 100644
--- a/tests/auto/qml/qqmlecmascript/tst_qqmlecmascript.cpp
+++ b/tests/auto/qml/qqmlecmascript/tst_qqmlecmascript.cpp
@@ -208,6 +208,7 @@ private slots:
     void dynamicCreationOwnership();
     void regExpBug();
     void nullObjectBinding();
+    void nullObjectInitializer();
     void deletedEngine();
     void libraryScriptAssert();
     void variantsAssignedUndefined();
@@ -5707,6 +5708,49 @@ void tst_qqmlecmascript::nullObjectBinding()
     delete object;
 }
 
+void tst_qqmlecmascript::nullObjectInitializer()
+{
+    {
+        QQmlComponent component(&engine, testFileUrl("nullObjectInitializer.qml"));
+        QScopedPointer<QObject> obj(component.create());
+        QVERIFY(!obj.isNull());
+
+        QQmlData *ddata = QQmlData::get(obj.data(), /*create*/false);
+        QVERIFY(ddata);
+
+        {
+            const int propertyIndex = obj->metaObject()->indexOfProperty("testProperty");
+            QVERIFY(propertyIndex > 0);
+            QVERIFY(!ddata->hasBindingBit(propertyIndex));
+        }
+
+        QVariant value = obj->property("testProperty");
+        QVERIFY(value.userType() == qMetaTypeId<QObject*>());
+        QVERIFY(!value.value<QObject*>());
+    }
+
+    {
+        QQmlComponent component(&engine, testFileUrl("nullObjectInitializer.2.qml"));
+        QScopedPointer<QObject> obj(component.create());
+        QVERIFY(!obj.isNull());
+
+        QQmlData *ddata = QQmlData::get(obj.data(), /*create*/false);
+        QVERIFY(ddata);
+
+        {
+            const int propertyIndex = obj->metaObject()->indexOfProperty("testProperty");
+            QVERIFY(propertyIndex > 0);
+            QVERIFY(ddata->hasBindingBit(propertyIndex));
+        }
+
+        QVERIFY(obj->property("success").toBool());
+
+        QVariant value = obj->property("testProperty");
+        QVERIFY(value.userType() == qMetaTypeId<QObject*>());
+        QVERIFY(!value.value<QObject*>());
+    }
+}
+
 // Test that bindings don't evaluate once the engine has been destroyed
 void tst_qqmlecmascript::deletedEngine()
 {