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>

1 files changed, 5 insertions, 2 deletions

diff --git a/src/qml/qml/qqmlcomponent_p.h b/src/qml/qml/qqmlcomponent_p.h
index 2170646b89..8ae7672c19 100644
--- a/src/qml/qml/qqmlcomponent_p.h
+++ b/src/qml/qml/qqmlcomponent_p.h
@@ -86,8 +86,9 @@ public:
 
     QObject *beginCreate(QQmlContextData *);
     void completeCreate();
-    void initializeObjectWithInitialProperties(QV4::QmlContext *qmlContext, const QV4::Value &valuemap, QObject *toCreate);
-    static void setInitialProperties(QV4::ExecutionEngine *engine, QV4::QmlContext *qmlContext, const QV4::Value &o, const QV4::Value &v);
+    void initializeObjectWithInitialProperties(QV4::QmlContext *qmlContext, const QV4::Value &valuemap, QObject *toCreate, RequiredProperties &requiredProperties);
+    static void setInitialProperties(QV4::ExecutionEngine *engine, QV4::QmlContext *qmlContext, const QV4::Value &o, const QV4::Value &v, RequiredProperties &requiredProperties, QObject *createdComponent);
+    static QQmlError unsetRequiredPropertyToQQmlError(const RequiredPropertyInfo &unsetRequiredProperty);
 
     virtual void incubateObject(
             QQmlIncubator *incubationTask,
@@ -106,6 +107,7 @@ public:
     qreal progress;
 
     int start;
+    RequiredProperties& requiredProperties();
     QQmlRefPointer<QV4::ExecutableCompilationUnit> compilationUnit;
 
     struct ConstructionState {
@@ -134,6 +136,7 @@ public:
     static void completeDeferred(QQmlEnginePrivate *enginePriv, DeferredState *deferredState);
 
     static void complete(QQmlEnginePrivate *enginePriv, ConstructionState *state);
+    static QQmlProperty removePropertyFromRequired(QObject *createdComponent, const QString &name, RequiredProperties& requiredProperties, bool *wasInRequiredProperties = nullptr);
 
     QQmlEngine *engine;
     QQmlGuardedContextData creationContext;