Long live QML inline components

[ChangeLog][QtQml] It is now possible to declare new QML components in
a QML file via the component keyword. They can be used just as if they
were declared in another file, with the only difference that the type
name needs to be prefixed with the name of the containing type outside
of the file were the inline component has been declared.

Notably, inline components are not closures: In the following
example, the output would be 42

// MyItem.qml
Item {
    property int i: 33
    component IC: Item {
        Component.onCompleted: console.log(i)
    }
}
// user.qml
Item {
    property int i: 42
    MyItem.IC {}
}

Fixes: QTBUG-79382
Change-Id: I6a5ffc43f093a76323f435cfee9bab217781b8f5
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>

1 files changed, 41 insertions, 18 deletions

diff --git a/src/qml/qml/qqmlobjectcreator.cpp b/src/qml/qml/qqmlobjectcreator.cpp
index 78df02554c..198ce98f2d 100644
--- a/src/qml/qml/qqmlobjectcreator.cpp
+++ b/src/qml/qml/qqmlobjectcreator.cpp
@@ -62,6 +62,7 @@
 #include <QScopedValueRollback>
 
 #include <qtqml_tracepoints_p.h>
+#include <QScopedValueRollback>
 
 QT_USE_NAMESPACE
 
@@ -77,9 +78,9 @@ QQmlObjectCreator::QQmlObjectCreator(QQmlContextData *parentContext, const QQmlR
     init(parentContext);
 
     sharedState->componentAttached = nullptr;
-    sharedState->allCreatedBindings.allocate(compilationUnit->totalBindingsCount);
-    sharedState->allParserStatusCallbacks.allocate(compilationUnit->totalParserStatusCount);
-    sharedState->allCreatedObjects.allocate(compilationUnit->totalObjectCount);
+    sharedState->allCreatedBindings.allocate(compilationUnit->totalBindingsCount());
+    sharedState->allParserStatusCallbacks.allocate(compilationUnit->totalParserStatusCount());
+    sharedState->allCreatedObjects.allocate(compilationUnit->totalObjectCount());
     sharedState->allJavaScriptObjects = nullptr;
     sharedState->creationContext = creationContext;
     sharedState->rootContext = nullptr;
@@ -87,7 +88,7 @@ QQmlObjectCreator::QQmlObjectCreator(QQmlContextData *parentContext, const QQmlR
 
     if (auto profiler = QQmlEnginePrivate::get(engine)->profiler) {
         Q_QML_PROFILE_IF_ENABLED(QQmlProfilerDefinitions::ProfileCreating, profiler,
-                sharedState->profiler.init(profiler, compilationUnit->totalParserStatusCount));
+                sharedState->profiler.init(profiler, compilationUnit->totalParserStatusCount()));
     } else {
         Q_UNUSED(profiler);
     }
@@ -145,7 +146,7 @@ QQmlObjectCreator::~QQmlObjectCreator()
     }
 }
 
-QObject *QQmlObjectCreator::create(int subComponentIndex, QObject *parent, QQmlInstantiationInterrupt *interrupt)
+QObject *QQmlObjectCreator::create(int subComponentIndex, QObject *parent, QQmlInstantiationInterrupt *interrupt, int flags)
 {
     if (phase == CreatingObjectsPhase2) {
         phase = ObjectsCreated;
@@ -159,14 +160,20 @@ QObject *QQmlObjectCreator::create(int subComponentIndex, QObject *parent, QQmlI
     if (subComponentIndex == -1) {
         objectToCreate = /*root object*/0;
     } else {
-        const QV4::CompiledData::Object *compObj = compilationUnit->objectAt(subComponentIndex);
-        objectToCreate = compObj->bindingTable()->value.objectIndex;
+        Q_ASSERT(subComponentIndex >= 0);
+        if (flags & CreationFlags::InlineComponent) {
+            objectToCreate = subComponentIndex;
+        } else {
+            Q_ASSERT(flags & CreationFlags::NormalObject);
+            const QV4::CompiledData::Object *compObj = compilationUnit->objectAt(subComponentIndex);
+            objectToCreate = compObj->bindingTable()->value.objectIndex;
+        }
     }
 
     context = new QQmlContextData;
     context->isInternal = true;
     context->imports = compilationUnit->typeNameCache;
-    context->initFromTypeCompilationUnit(compilationUnit, subComponentIndex);
+    context->initFromTypeCompilationUnit(compilationUnit, flags & CreationFlags::NormalObject ? subComponentIndex : -1);
     context->setParent(parentContext);
 
     if (!sharedState->rootContext) {
@@ -179,7 +186,7 @@ QObject *QQmlObjectCreator::create(int subComponentIndex, QObject *parent, QQmlI
 
     Q_ASSERT(sharedState->allJavaScriptObjects || topLevelCreator);
     if (topLevelCreator)
-        sharedState->allJavaScriptObjects = scope.alloc(compilationUnit->totalObjectCount);
+        sharedState->allJavaScriptObjects = scope.alloc(compilationUnit->totalObjectCount());
 
     if (subComponentIndex == -1 && compilationUnit->dependentScripts.count()) {
         QV4::ScopedObject scripts(scope, v4->newArrayObject(compilationUnit->dependentScripts.count()));
@@ -231,6 +238,9 @@ void QQmlObjectCreator::beginPopulateDeferred(QQmlContextData *newContext)
 
     Q_ASSERT(topLevelCreator);
     Q_ASSERT(!sharedState->allJavaScriptObjects);
+
+    QV4::Scope valueScope(v4);
+    sharedState->allJavaScriptObjects = valueScope.alloc(compilationUnit->totalObjectCount());
 }
 
 void QQmlObjectCreator::populateDeferred(QObject *instance, int deferredIndex,
@@ -248,7 +258,7 @@ void QQmlObjectCreator::populateDeferred(QObject *instance, int deferredIndex,
 
     QV4::Scope valueScope(v4);
     QScopedValueRollback<QV4::Value*> jsObjectGuard(sharedState->allJavaScriptObjects,
-                                                    valueScope.alloc(compilationUnit->totalObjectCount));
+                                                    valueScope.alloc(compilationUnit->totalObjectCount()));
 
     Q_ASSERT(topLevelCreator);
     QV4::QmlContext *qmlContext = static_cast<QV4::QmlContext *>(valueScope.alloc());
@@ -263,7 +273,6 @@ void QQmlObjectCreator::populateDeferred(QObject *instance, int deferredIndex,
 
     const QV4::CompiledData::Object *obj = compilationUnit->objectAt(_compiledObjectIndex);
     qSwap(_compiledObject, obj);
-
     qSwap(_ddata, declarativeData);
     qSwap(_bindingTarget, bindingTarget);
     qSwap(_vmeMetaObject, vmeMetaObject);
@@ -1172,7 +1181,7 @@ QObject *QQmlObjectCreator::createInstance(int index, QObject *parent, bool isCo
         Q_ASSERT(typeRef);
         installPropertyCache = !typeRef->isFullyDynamicType;
         QQmlType type = typeRef->type;
-        if (type.isValid()) {
+        if (type.isValid() && !type.isInlineComponentType()) {
             typeName = type.qmlTypeName();
 
             void *ddataMemory = nullptr;
@@ -1206,17 +1215,31 @@ QObject *QQmlObjectCreator::createInstance(int index, QObject *parent, bool isCo
         } else {
             Q_ASSERT(typeRef->compilationUnit);
             typeName = typeRef->compilationUnit->fileName();
-            if (typeRef->compilationUnit->unitData()->isSingleton())
+            // compilation unit is shared between root type and its inline component types
+            // so isSingleton errorneously returns true for inline components
+            if (typeRef->compilationUnit->unitData()->isSingleton() && !type.isInlineComponentType())
             {
                 recordError(obj->location, tr("Composite Singleton Type %1 is not creatable").arg(stringAt(obj->inheritedTypeNameIndex)));
                 return nullptr;
             }
 
-            QQmlObjectCreator subCreator(context, typeRef->compilationUnit, sharedState.data());
-            instance = subCreator.create();
-            if (!instance) {
-                errors += subCreator.errors;
-                return nullptr;
+
+            if (!type.isInlineComponentType()) {
+                QQmlObjectCreator subCreator(context, typeRef->compilationUnit, sharedState.data());
+                instance = subCreator.create();
+                if (!instance) {
+                    errors += subCreator.errors;
+                    return nullptr;
+                }
+            } else {
+                int subObjectId = type.inlineComponendId();
+                QScopedValueRollback<int> rollback {typeRef->compilationUnit->icRoot, subObjectId};
+                QQmlObjectCreator subCreator(context, typeRef->compilationUnit, sharedState.data());
+                instance = subCreator.create(subObjectId, nullptr, nullptr, CreationFlags::InlineComponent);
+                if (!instance) {
+                    errors += subCreator.errors;
+                    return nullptr;
+                }
             }
         }
         if (instance->isWidgetType()) {