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>

2 files changed, 72 insertions, 3 deletions

diff --git a/src/qml/compiler/qqmlirbuilder.cpp b/src/qml/compiler/qqmlirbuilder.cpp
index 9623d2ed58..811f88cb73 100644
--- a/src/qml/compiler/qqmlirbuilder.cpp
+++ b/src/qml/compiler/qqmlirbuilder.cpp
@@ -161,6 +161,7 @@ void Object::init(QQmlJS::MemoryPool *pool, int typeNameIndex, int idIndex, cons
     bindings = pool->New<PoolList<Binding> >();
     functions = pool->New<PoolList<Function> >();
     functionsAndExpressions = pool->New<PoolList<CompiledFunctionOrExpression> >();
+    inlineComponents = pool->New<PoolList<InlineComponent>>();
     declarationsOverride = nullptr;
 }
 
@@ -281,6 +282,11 @@ void Object::appendFunction(QmlIR::Function *f)
     target->functions->append(f);
 }
 
+void Object::appendInlineComponent(InlineComponent *ic)
+{
+    inlineComponents->append(ic);
+}
+
 QString Object::appendBinding(Binding *b, bool isListBinding)
 {
     const bool bindingToDefaultProperty = (b->propertyNameIndex == quint32(0));
@@ -503,6 +509,33 @@ bool IRBuilder::visit(QQmlJS::AST::UiObjectDefinition *node)
     return false;
 }
 
+bool IRBuilder::visit(QQmlJS::AST::UiInlineComponent *ast)
+{
+    int idx = -1;
+    if (insideInlineComponent) {
+        recordError(ast->firstSourceLocation(), QLatin1String("Nested inline components are not supported"));
+        return false;
+    }
+    {
+        QScopedValueRollback<bool> rollBack {insideInlineComponent, true};
+        if (!defineQMLObject(&idx, ast->component))
+            return false;
+    }
+    Q_ASSERT(idx > 0);
+    Object* definedObject = _objects.at(idx);
+    definedObject->flags |= QV4::CompiledData::Object::IsInlineComponentRoot;
+    definedObject->flags |= QV4::CompiledData::Object::InPartOfInlineComponent;
+    definedObject->isInlineComponent = true;
+    auto inlineComponent = New<InlineComponent>();
+    inlineComponent->nameIndex = registerString(ast->name.toString());
+    inlineComponent->objectIndex = idx;
+    auto location = ast->firstSourceLocation();
+    inlineComponent->location.line = location.startLine;
+    inlineComponent->location.column = location.startColumn;
+    _object->appendInlineComponent(inlineComponent);
+    return false;
+}
+
 bool IRBuilder::visit(QQmlJS::AST::UiObjectBinding *node)
 {
     int idx = 0;
@@ -597,12 +630,16 @@ bool IRBuilder::defineQMLObject(int *objectIndex, QQmlJS::AST::UiQualifiedId *qu
     }
 
     Object *obj = New<Object>();
+
     _objects.append(obj);
     *objectIndex = _objects.size() - 1;
     qSwap(_object, obj);
 
     _object->init(pool, registerString(asString(qualifiedTypeNameId)), emptyStringIndex, location);
     _object->declarationsOverride = declarationsOverride;
+    if (insideInlineComponent) {
+        _object->flags |= QV4::CompiledData::Object::InPartOfInlineComponent;
+    }
 
     // A new object is also a boundary for property declarations.
     Property *declaration = nullptr;
@@ -1553,7 +1590,7 @@ void QmlUnitGenerator::generate(Document &output, const QV4::CompiledData::Depen
     uint nextOffset = objectOffset + objectOffsetTableSize;
     for (Object *o : qAsConst(output.objects)) {
         objectOffsets.insert(o, nextOffset);
-        nextOffset += QV4::CompiledData::Object::calculateSizeExcludingSignalsAndEnums(o->functionCount(), o->propertyCount(), o->aliasCount(), o->enumCount(), o->signalCount(), o->bindingCount(), o->namedObjectsInComponent.size());
+        nextOffset += QV4::CompiledData::Object::calculateSizeExcludingSignalsAndEnums(o->functionCount(), o->propertyCount(), o->aliasCount(), o->enumCount(), o->signalCount(), o->bindingCount(), o->namedObjectsInComponent.size(), o->inlineComponentCount());
 
         int signalTableSize = 0;
         for (const Signal *s = o->firstSignal(); s; s = s->next)
@@ -1632,6 +1669,10 @@ void QmlUnitGenerator::generate(Document &output, const QV4::CompiledData::Depen
         objectToWrite->offsetToNamedObjectsInComponent = nextOffset;
         nextOffset += objectToWrite->nNamedObjectsInComponent * sizeof(quint32);
 
+        objectToWrite->nInlineComponents = o->inlineComponentCount();
+        objectToWrite->offsetToInlineComponents = nextOffset;
+        nextOffset += objectToWrite->nInlineComponents * sizeof (QV4::CompiledData::InlineComponent);
+
         quint32_le *functionsTable = reinterpret_cast<quint32_le *>(objectPtr + objectToWrite->offsetToFunctions);
         for (const Function *f = o->firstFunction(); f; f = f->next)
             *functionsTable++ = o->runtimeFunctionIndices.at(f->index);
@@ -1703,6 +1744,14 @@ void QmlUnitGenerator::generate(Document &output, const QV4::CompiledData::Depen
         for (int i = 0; i < o->namedObjectsInComponent.size(); ++i) {
             *namedObjectInComponentPtr++ = o->namedObjectsInComponent.at(i);
         }
+
+        char *inlineComponentPtr = objectPtr + objectToWrite->offsetToInlineComponents;
+        for (auto it = o->inlineComponentsBegin(); it != o->inlineComponentsEnd(); ++it) {
+            const InlineComponent *ic = it.ptr;
+            QV4::CompiledData::InlineComponent *icToWrite = reinterpret_cast<QV4::CompiledData::InlineComponent*>(inlineComponentPtr);
+            *icToWrite = *ic;
+            inlineComponentPtr += sizeof(QV4::CompiledData::InlineComponent);
+        }
     }
 
     if (!output.javaScriptCompilationUnit.data) {
@@ -1850,12 +1899,14 @@ bool JSCodeGen::generateCodeForComponents(const QVector<quint32> &componentRoots
 bool JSCodeGen::compileComponent(int contextObject)
 {
     const QmlIR::Object *obj = document->objects.at(contextObject);
-    if (obj->flags & QV4::CompiledData::Object::IsComponent) {
+    if (obj->flags & QV4::CompiledData::Object::IsComponent && !obj->isInlineComponent) {
         Q_ASSERT(obj->bindingCount() == 1);
         const QV4::CompiledData::Binding *componentBinding = obj->firstBinding();
         Q_ASSERT(componentBinding->type == QV4::CompiledData::Binding::Type_Object);
         contextObject = componentBinding->value.objectIndex;
     }
+    for (auto it = obj->inlineComponentsBegin(); it != obj->inlineComponentsEnd(); ++it)
+        compileComponent(it->objectIndex);
 
     return compileJavaScriptCodeInObjectsRecursively(contextObject, contextObject);
 }
@@ -1863,7 +1914,7 @@ bool JSCodeGen::compileComponent(int contextObject)
 bool JSCodeGen::compileJavaScriptCodeInObjectsRecursively(int objectIndex, int scopeObjectIndex)
 {
     QmlIR::Object *object = document->objects.at(objectIndex);
-    if (object->flags & QV4::CompiledData::Object::IsComponent)
+    if (object->flags & QV4::CompiledData::Object::IsComponent && !object->isInlineComponent)
         return true;
 
     if (object->functionsAndExpressions->count > 0) {
diff --git a/src/qml/compiler/qqmlirbuilder_p.h b/src/qml/compiler/qqmlirbuilder_p.h
index ab0ddf6ef8..d4f2eb8dd4 100644
--- a/src/qml/compiler/qqmlirbuilder_p.h
+++ b/src/qml/compiler/qqmlirbuilder_p.h
@@ -275,6 +275,11 @@ struct Binding : public QV4::CompiledData::Binding
     Binding *next;
 };
 
+struct InlineComponent : public QV4::CompiledData::InlineComponent
+{
+    InlineComponent *next;
+};
+
 struct Alias : public QV4::CompiledData::Alias
 {
     Alias *next;
@@ -316,6 +321,7 @@ public:
     int id;
     int indexOfDefaultPropertyOrAlias;
     bool defaultPropertyIsAlias;
+    bool isInlineComponent = false;
     quint32 flags;
 
     QV4::CompiledData::Location location;
@@ -333,6 +339,8 @@ public:
     int bindingCount() const { return bindings->count; }
     const Function *firstFunction() const { return functions->first; }
     int functionCount() const { return functions->count; }
+    const InlineComponent *inlineComponent() const { return inlineComponents->first; }
+    int inlineComponentCount() const { return inlineComponents->count; }
 
     PoolList<Binding>::Iterator bindingsBegin() const { return bindings->begin(); }
     PoolList<Binding>::Iterator bindingsEnd() const { return bindings->end(); }
@@ -346,6 +354,8 @@ public:
     PoolList<Signal>::Iterator signalsEnd() const { return qmlSignals->end(); }
     PoolList<Function>::Iterator functionsBegin() const { return functions->begin(); }
     PoolList<Function>::Iterator functionsEnd() const { return functions->end(); }
+    PoolList<InlineComponent>::Iterator inlineComponentsBegin() const { return inlineComponents->begin(); }
+    PoolList<InlineComponent>::Iterator inlineComponentsEnd() const { return inlineComponents->end(); }
 
     // If set, then declarations for this object (and init bindings for these) should go into the
     // specified object. Used for declarations inside group properties.
@@ -358,6 +368,7 @@ public:
     QString appendProperty(Property *prop, const QString &propertyName, bool isDefaultProperty, const QQmlJS::AST::SourceLocation &defaultToken, QQmlJS::AST::SourceLocation *errorLocation);
     QString appendAlias(Alias *prop, const QString &aliasName, bool isDefaultProperty, const QQmlJS::AST::SourceLocation &defaultToken, QQmlJS::AST::SourceLocation *errorLocation);
     void appendFunction(QmlIR::Function *f);
+    void appendInlineComponent(InlineComponent *ic);
 
     QString appendBinding(Binding *b, bool isListBinding);
     Binding *findBinding(quint32 nameIndex) const;
@@ -381,6 +392,7 @@ private:
     PoolList<Signal> *qmlSignals;
     PoolList<Binding> *bindings;
     PoolList<Function> *functions;
+    PoolList<InlineComponent> *inlineComponents;
 };
 
 struct Q_QMLCOMPILER_PRIVATE_EXPORT Pragma
@@ -409,6 +421,9 @@ struct Q_QMLCOMPILER_PRIVATE_EXPORT Document
 
     int registerString(const QString &str) { return jsGenerator.registerString(str); }
     QString stringAt(int index) const { return jsGenerator.stringForIndex(index); }
+
+    int objectCount() const {return objects.size();}
+    Object* objectAt(int i) const {return objects.at(i);}
 };
 
 class Q_QMLCOMPILER_PRIVATE_EXPORT ScriptDirectivesCollector : public QQmlJS::Directives
@@ -449,6 +464,7 @@ public:
     bool visit(QQmlJS::AST::UiArrayBinding *ast) override;
     bool visit(QQmlJS::AST::UiObjectBinding *ast) override;
     bool visit(QQmlJS::AST::UiObjectDefinition *ast) override;
+    bool visit(QQmlJS::AST::UiInlineComponent *ast) override;
     bool visit(QQmlJS::AST::UiEnumDeclaration *ast) override;
     bool visit(QQmlJS::AST::UiPublicMember *ast) override;
     bool visit(QQmlJS::AST::UiScriptBinding *ast) override;
@@ -527,6 +543,8 @@ public:
     QQmlJS::MemoryPool *pool;
     QString sourceCode;
     QV4::Compiler::JSUnitGenerator *jsGenerator;
+
+    bool insideInlineComponent = false;
 };
 
 struct Q_QMLCOMPILER_PRIVATE_EXPORT QmlUnitGenerator