qmltc: Support Component roots

It is a very special case that doesn't undergo a normal compilation but
instead just uses QQmlObjectCreator::createComponent() logic.
As QQmlObjectCreator::createComponent() returns a new QQmlComponent,
we can't use it within the qmltc-generated type's ctor. Instead, just
fake the same flow by incorporating the code into the qmltc type
setting

As a drive-by, fix the code to work correctly with Component roots.
This should now pretty much cover all the mystical logic of
QQmlComponentAndAliasResolver and, with tests, we can safely simplify
the qmltc code generator bits later without introducing bugs

Enhance tst_qqmlcomponent::componentTypes test to highlight that
property Component p: ComponentDerivedType {} is not marked with
QV4::CompiledData::Object::IsComponent flag at all and thus considered
to be an ordinary object binding, unlike
property Component p: NotComponentDerivedType {}

Change-Id: I4ec41952d15f9659d316e44dab4050aa4908327c
Reviewed-by: Fawzi Mohamed <fawzi.mohamed@qt.io>
(cherry picked from commit 39aee682bf388e191a409485cbbe2e01996bc163)
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>

1 files changed, 116 insertions, 50 deletions

diff --git a/tools/qmltc/prototype/codegenerator.cpp b/tools/qmltc/prototype/codegenerator.cpp
index 8a304d7d72..747db452e9 100644
--- a/tools/qmltc/prototype/codegenerator.cpp
+++ b/tools/qmltc/prototype/codegenerator.cpp
@@ -287,6 +287,11 @@ void CodeGenerator::constructObjects(QSet<QString> &requiredCppIncludes)
         m_immediateParents = findImmediateParents(context, objects);
     };
     executor.addPass(setImmediateParents);
+    const auto setIgnoredTypes = [&](const Qml2CppContext &context, QList<Qml2CppObject> &objects) {
+        m_ignoredTypes = collectIgnoredTypes(context, objects);
+    };
+    executor.addPass(setIgnoredTypes);
+
     // run all passes:
     executor.run(m_logger);
 }
@@ -313,35 +318,48 @@ void CodeGenerator::generate(const Options &options)
     if (m_logger->hasErrors() || m_logger->hasWarnings())
         return;
 
-    const auto isWithinSubComponent = [&](QQmlJSScope::ConstPtr type) {
-        for (; type; type = type->parentScope()) {
-            qsizetype index = m_typeToObjectIndex.value(type, -1);
-            if (index < 0)
-                return false;
-            const QmlIR::Object *irObject = m_objects[index].irObject;
-            if (irObject->flags & QV4::CompiledData::Object::IsComponent)
-                return true;
-        }
-        return false;
+    if (m_objects.isEmpty()) {
+        recordError(QQmlJS::SourceLocation(), u"No relevant QML types to compile."_qs);
+        return;
+    }
+
+    const auto isComponent = [](const QQmlJSScope::ConstPtr &type) {
+        auto base = type->baseType();
+        return base && base->internalName() == u"QQmlComponent"_qs;
     };
+    const auto &root = m_objects.at(0).type;
 
-    // compile everything
     QList<QQmlJSAotObject> compiledObjects;
-    compiledObjects.reserve(m_objects.size());
-    for (const auto &object : m_objects) {
-        if (object.type->scopeType() != QQmlJSScope::QMLScope) {
-            qCDebug(lcCodeGenerator) << u"Scope '" + object.type->internalName()
-                            + u"' is not QMLScope, so it is skipped.";
-            continue;
-        }
-        if (isWithinSubComponent(object.type)) {
-            // e.g. when creating a view delegate
-            qCDebug(lcCodeGenerator) << u"Scope '" + object.type->internalName()
-                            + u"' is a QQmlComponent sub-component. It won't be compiled to C++.";
-            continue;
-        }
+    if (isComponent(root)) {
+        compiledObjects.reserve(1);
         compiledObjects.emplaceBack(); // create new object
-        compileObject(compiledObjects.back(), object);
+        const auto compile = [this](QQmlJSAotObject &current, const CodeGenObject &object) {
+            this->compileQQmlComponentElements(current, object);
+        };
+        compileObject(compiledObjects.back(), m_objects.at(0), compile);
+    } else {
+        const auto compile = [this](QQmlJSAotObject &current, const CodeGenObject &object) {
+            this->compileObjectElements(current, object);
+        };
+
+        // compile everything
+        compiledObjects.reserve(m_objects.size());
+        for (const auto &object : m_objects) {
+            if (object.type->scopeType() != QQmlJSScope::QMLScope) {
+                qCDebug(lcCodeGenerator) << u"Scope '" + object.type->internalName()
+                                + u"' is not QMLScope, so it is skipped.";
+                continue;
+            }
+            if (m_ignoredTypes.contains(object.type)) {
+                // e.g. object.type is a view delegate
+                qCDebug(lcCodeGenerator) << u"Scope '" + object.type->internalName()
+                                + u"' is a QQmlComponent sub-component. It won't be compiled to "
+                                  u"C++.";
+                continue;
+            }
+            compiledObjects.emplaceBack(); // create new object
+            compileObject(compiledObjects.back(), object, compile);
+        }
     }
     // no point in generating anything if there are errors
     if (m_logger->hasErrors() || m_logger->hasWarnings())
@@ -369,7 +387,9 @@ QString buildCallSpecialMethodValue(bool documentRoot, const QString &outerFlagN
     }
 }
 
-void CodeGenerator::compileObject(QQmlJSAotObject &compiled, const CodeGenObject &object)
+void CodeGenerator::compileObject(
+        QQmlJSAotObject &compiled, const CodeGenObject &object,
+        std::function<void(QQmlJSAotObject &, const CodeGenObject &)> compileElements)
 {
     compiled.cppType = object.type->internalName();
     const QString baseClass = object.type->baseType()->internalName();
@@ -634,6 +654,36 @@ void CodeGenerator::compileObject(QQmlJSAotObject &compiled, const CodeGenObject
         (m_isAnonymous ? u"QML_ANONYMOUS"_qs : u"QML_ELEMENT"_qs),
     };
 
+    compileElements(compiled, object);
+
+    // add finalization steps only to document root
+    if (documentRoot) {
+        compiled.endInit.body << u"if (" + finalizeFlag.name + u") {";
+
+        // at this point, all bindings must've been finished, thus, we need:
+        // 1. componentComplete()
+        // 2. finalize callbacks / componentFinalized()
+        // 3. Component.onCompleted()
+
+        // 1.
+        compiled.endInit.body << u"    this->" + compiled.completeComponent.name
+                        + u"(/* complete component */ true);";
+
+        // 2
+        compiled.endInit.body << u"    this->" + compiled.finalizeComponent.name
+                        + u"(/* finalize component */ true);";
+
+        // 3.
+        compiled.endInit.body << u"    this->" + compiled.handleOnCompleted.name + u"();";
+
+        compiled.endInit.body << u"}"_qs;
+    }
+
+    // compiled.endInit.body << u"Qt::endPropertyUpdateGroup();"_qs;
+}
+
+void CodeGenerator::compileObjectElements(QQmlJSAotObject &compiled, const CodeGenObject &object)
+{
     if (object.type->isSingleton()) {
         if (m_isAnonymous) {
             recordError(object.type->sourceLocation(),
@@ -735,32 +785,48 @@ void CodeGenerator::compileObject(QQmlJSAotObject &compiled, const CodeGenObject
 
     for (; it != sortedBindings.cend(); ++it)
         compileBinding(compiled, **it, object, { object.type, u"this"_qs, u""_qs, false });
+}
 
-    // add finalization steps only to document root
-    if (documentRoot) {
-        compiled.endInit.body << u"if (" + finalizeFlag.name + u") {";
-
-        // at this point, all bindings must've been finished, thus, we need:
-        // 1. componentComplete()
-        // 2. finalize callbacks / componentFinalized()
-        // 3. Component.onCompleted()
-
-        // 1.
-        compiled.endInit.body << u"    this->" + compiled.completeComponent.name
-                        + u"(/* complete component */ true);";
-
-        // 2
-        compiled.endInit.body << u"    this->" + compiled.finalizeComponent.name
-                        + u"(/* finalize component */ true);";
-
-        // 3.
-        compiled.endInit.body << u"    this->" + compiled.handleOnCompleted.name + u"();";
-
-        compiled.endInit.body << u"}"_qs;
+void CodeGenerator::compileQQmlComponentElements(QQmlJSAotObject &compiled,
+                                                 const CodeGenObject &object)
+{
+    if (object.type->isSingleton()) {
+        // it is unclear what to do with singletons in general, so just reject
+        recordError(object.type->sourceLocation(),
+                    QStringLiteral(u"Singleton Component-based types are not supported"));
+        return;
     }
 
-    // compiled.endInit.body << u"Qt::endPropertyUpdateGroup();"_qs;
+    // since we create a document root as QQmlComponent, we only need to fake
+    // QQmlComponent construction in init:
+    compiled.init.body << u"// populate QQmlComponent bits"_qs;
+    compiled.init.body << u"{"_qs;
+    // we already called QQmlComponent(parent) constructor. now we need:
+    // 1. QQmlComponent(engine, parent) logic:
+    compiled.init.body << u"// QQmlComponent(engine, parent):"_qs;
+    compiled.init.body << u"auto d = QQmlComponentPrivate::get(this);"_qs;
+    compiled.init.body << u"Q_ASSERT(d);"_qs;
+    compiled.init.body << u"d->engine = engine;"_qs;
+    compiled.init.body << u"QObject::connect(engine, &QObject::destroyed, this, [d]() {"_qs;
+    compiled.init.body << u"    d->state.creator.reset();"_qs;
+    compiled.init.body << u"    d->engine = nullptr;"_qs;
+    compiled.init.body << u"});"_qs;
+    // 2. QQmlComponent(engine, compilationUnit, start, parent) logic:
+    compiled.init.body << u"// QQmlComponent(engine, compilationUnit, start, parent):"_qs;
+    compiled.init.body
+            << u"auto compilationUnit = QQmlEnginePrivate::get(engine)->compilationUnitFromUrl("
+                    + m_urlMethod.name + u"());";
+    compiled.init.body << u"d->compilationUnit = compilationUnit;"_qs;
+    compiled.init.body << u"d->start = 0;"_qs;
+    compiled.init.body << u"d->url = compilationUnit->finalUrl();"_qs;
+    compiled.init.body << u"d->progress = 1.0;"_qs;
+    // 3. QQmlObjectCreator::createComponent() logic which is left:
+    compiled.init.body << u"// QQmlObjectCreator::createComponent():"_qs;
+    compiled.init.body << u"d->creationContext = context;"_qs;
+    compiled.init.body << u"Q_ASSERT(QQmlData::get(this, /*create*/ false));"_qs;
+    compiled.init.body << u"}"_qs;
 }
+
 void CodeGenerator::compileEnum(QQmlJSAotObject &current, const QQmlJSMetaEnum &e)
 {
     const auto intValues = e.values();
@@ -1271,12 +1337,12 @@ void CodeGenerator::compileBinding(QQmlJSAotObject &current, const QmlIR::Bindin
             current.endInit.body << QStringLiteral("thisContext->installContext(QQmlData::get(%1), "
                                                    "QQmlContextData::OrdinaryObject);")
                                             .arg(objectName);
-            const auto isExplicitComponent = [](const QQmlJSScope::ConstPtr &type) {
+            const auto isComponentBased = [](const QQmlJSScope::ConstPtr &type) {
                 auto base = QQmlJSScope::nonCompositeBaseType(type);
                 return base && base->internalName() == u"QQmlComponent"_qs;
             };
             if (!m_doc->stringAt(bindingObject.irObject->idNameIndex).isEmpty()
-                && isExplicitComponent(bindingObject.type)) {
+                && isComponentBased(bindingObject.type)) {
                 current.endInit.body
                         << CodeGeneratorUtility::generate_setIdValue(
                                    u"thisContext"_qs, bindingObject.irObject->id, objectName,