Introduce required properties to QML

[ChangeLog][QtQml]
"required" is now a (contextual) keyword in QML, and users can
mark properties with it to specify that those properties must be set
when the component gets instantiated.
This can be done either declaratively via standard property
bindings from QML, or imperatively by using the functions to set initial
properties (QQmlCompoent::setInitalProperties and related functions in
C++, Qt.createObject, Loader.setSource,... in QML/JS).
Logic has been added to QQmlComponent::create and the various QQmlIncubator
classes to verify that the required properties were set. If properties
marked as required are not set, a warning will be printed at runtime,
and the component will not be created.

Change-Id: I8e38227fc8f173b053b689c1597dc7fd40e835e7
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

4 files changed, 58 insertions, 0 deletions

diff --git a/tests/auto/quick/qquickloader/data/RequiredPropertyValuesComponent.qml b/tests/auto/quick/qquickloader/data/RequiredPropertyValuesComponent.qml
new file mode 100644
index 0000000000..7bb21e8b93
--- /dev/null
+++ b/tests/auto/quick/qquickloader/data/RequiredPropertyValuesComponent.qml
@@ -0,0 +1,8 @@
+import QtQuick 2.0
+
+Item {
+    id: behaviorCounter
+    required property int i
+    required property string s
+
+}
diff --git a/tests/auto/quick/qquickloader/data/initialPropertyValues.10.qml b/tests/auto/quick/qquickloader/data/initialPropertyValues.10.qml
new file mode 100644
index 0000000000..4728346ca1
--- /dev/null
+++ b/tests/auto/quick/qquickloader/data/initialPropertyValues.10.qml
@@ -0,0 +1,20 @@
+import QtQuick 2.0
+
+Item {
+    id: root
+    property int i: 0
+    property string s: ""
+
+    Loader {
+        id: loader
+        objectName: "loader"
+        onLoaded: {
+            root.i = loader.item.i;         // should be 42
+            root.s = loader.item.s; // should be 11
+        }
+    }
+
+    Component.onCompleted: {
+        loader.setSource("RequiredPropertyValuesComponent.qml", {"i": 42});
+    }
+}
diff --git a/tests/auto/quick/qquickloader/data/initialPropertyValues.9.qml b/tests/auto/quick/qquickloader/data/initialPropertyValues.9.qml
new file mode 100644
index 0000000000..5d6e3171a0
--- /dev/null
+++ b/tests/auto/quick/qquickloader/data/initialPropertyValues.9.qml
@@ -0,0 +1,20 @@
+import QtQuick 2.0
+
+Item {
+    id: root
+    property int i: 0
+    property string s: ""
+
+    Loader {
+        id: loader
+        objectName: "loader"
+        onLoaded: {
+            root.i = loader.item.i;         // should be 42
+            root.s = loader.item.s; // should be 11
+        }
+    }
+
+    Component.onCompleted: {
+        loader.setSource("RequiredPropertyValuesComponent.qml", {"i": 42, "s": "hello world"});
+    }
+}
diff --git a/tests/auto/quick/qquickloader/tst_qquickloader.cpp b/tests/auto/quick/qquickloader/tst_qquickloader.cpp
index fbdd87905b..da923d4d41 100644
--- a/tests/auto/quick/qquickloader/tst_qquickloader.cpp
+++ b/tests/auto/quick/qquickloader/tst_qquickloader.cpp
@@ -681,6 +681,16 @@ void tst_QQuickLoader::initialPropertyValues_data()
             << QStringList()
             << (QStringList() << "initialValue")
             << (QVariantList() << 6);
+
+    QTest::newRow("ensure required properties are set correctly") << testFileUrl("initialPropertyValues.9.qml")
+            << QStringList()
+            << (QStringList() << "i" << "s")
+            << (QVariantList() << 42 << QLatin1String("hello world"));
+
+    QTest::newRow("required properties only partially set =") << testFileUrl("initialPropertyValues.10.qml")
+            << (QStringList() << QString(testFileUrl("RequiredPropertyValuesComponent.qml").toString() +  QLatin1String(":6:5: Required property s was not initialized")))
+            << (QStringList() << "i" << "s")
+            << (QVariantList() << 0 << QLatin1String(""));
 }
 
 void tst_QQuickLoader::initialPropertyValues()