Encapsulate QQmlContextData

This class is not a private detail of QQmlContext. And it is incredibly
hard to see who owns what in there. Let's add some civilization ...

We enforce refcounting for QQmlContextData across the code base, with
two exceptions:

1. QQmlContextPrivate may or may not own its QQmlContextData.
2. We may request a QQmlContextData owned by its parent QQmlContextData.

For these two cases we keep flags in QQmlContextData and when the
respective field (m_parent or m_publicContext) is reset, we release()
once.

Furthermore, QQmlContextData and QQmlGuardedContextData are moved to
their own files, in order to de-spaghettify qqmlcontext_p.h and
qqmlcontext.cpp.

When the QQmlEngine is deleted, any QQmlComponents drop their object
creators now, in order to release any context data held by those.
Before, the context data would be deleted, but the object creators would
retain the dangling pointer.

[ChangeLog][QML][Important Behavior Changes] QQmlContext::baseUrl() does
what the documentation says now: It prefers explicitly set baseUrls over
compilation unit URLs. Only if no baseUrl is set, the CU's URL is
returned. It used to prefer the CU's URL.

Change-Id: Ieeb5dcb07b45d891526191321386d5443b8f5738
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

1 files changed, 37 insertions, 33 deletions

diff --git a/src/qml/qml/qqmlscriptdata.cpp b/src/qml/qml/qqmlscriptdata.cpp
index ae268ca904..50ec0e20cd 100644
--- a/src/qml/qml/qqmlscriptdata.cpp
+++ b/src/qml/qml/qqmlscriptdata.cpp
@@ -55,78 +55,82 @@ QQmlScriptData::QQmlScriptData()
 {
 }
 
-QQmlContextData *QQmlScriptData::qmlContextDataForContext(QQmlContextData *parentQmlContextData)
+QQmlRefPointer<QQmlContextData> QQmlScriptData::qmlContextDataForContext(
+        const QQmlRefPointer<QQmlContextData> &parentQmlContextData)
 {
-    Q_ASSERT(parentQmlContextData && parentQmlContextData->engine);
+    Q_ASSERT(parentQmlContextData && parentQmlContextData->engine());
 
     if (m_precompiledScript->isESModule())
         return nullptr;
 
-    auto qmlContextData = new QQmlContextData();
+    QQmlRefPointer<QQmlContextData> qmlContextData = m_precompiledScript->isSharedLibrary()
+            ? QQmlContextData::createRefCounted(QQmlRefPointer<QQmlContextData>())
+            : QQmlContextData::createRefCounted(parentQmlContextData);
 
-    qmlContextData->isInternal = true;
-    qmlContextData->isJSContext = true;
+    qmlContextData->setInternal(true);
+    qmlContextData->setJSContext(true);
     if (m_precompiledScript->isSharedLibrary())
-        qmlContextData->isPragmaLibraryContext = true;
+        qmlContextData->setPragmaLibraryContext(true);
     else
-        qmlContextData->isPragmaLibraryContext = parentQmlContextData->isPragmaLibraryContext;
-    qmlContextData->baseUrl = url;
-    qmlContextData->baseUrlString = urlString;
+        qmlContextData->setPragmaLibraryContext(parentQmlContextData->isPragmaLibraryContext());
+    qmlContextData->setBaseUrl(url);
+    qmlContextData->setBaseUrlString(urlString);
 
     // For backward compatibility, if there are no imports, we need to use the
     // imports from the parent context.  See QTBUG-17518.
     if (!typeNameCache->isEmpty()) {
-        qmlContextData->imports = typeNameCache;
+        qmlContextData->setImports(typeNameCache);
     } else if (!m_precompiledScript->isSharedLibrary()) {
-        qmlContextData->imports = parentQmlContextData->imports;
-        qmlContextData->importedScripts = parentQmlContextData->importedScripts;
+        qmlContextData->setImports(parentQmlContextData->imports());
+        qmlContextData->setImportedScripts(parentQmlContextData->importedScripts());
     }
 
-    if (!m_precompiledScript->isSharedLibrary()) {
-        qmlContextData->setParent(parentQmlContextData);
-    } else {
-        qmlContextData->engine = parentQmlContextData->engine; // Fix for QTBUG-21620
-    }
+    if (m_precompiledScript->isSharedLibrary())
+        qmlContextData->setEngine(parentQmlContextData->engine()); // Fix for QTBUG-21620
 
-    QV4::ExecutionEngine *v4 = parentQmlContextData->engine->handle();
+    QV4::ExecutionEngine *v4 = parentQmlContextData->engine()->handle();
     QV4::Scope scope(v4);
     QV4::ScopedObject scriptsArray(scope);
-    if (qmlContextData->importedScripts.isNullOrUndefined()) {
+    if (qmlContextData->importedScripts().isNullOrUndefined()) {
         scriptsArray = v4->newArrayObject(scripts.count());
-        qmlContextData->importedScripts.set(v4, scriptsArray);
+        qmlContextData->setImportedScripts(
+                    QV4::PersistentValue(v4, scriptsArray.asReturnedValue()));
     } else {
-        scriptsArray = qmlContextData->importedScripts.valueRef();
+        scriptsArray = qmlContextData->importedScripts().valueRef();
     }
     QV4::ScopedValue v(scope);
-    for (int ii = 0; ii < scripts.count(); ++ii)
-        scriptsArray->put(ii, (v = scripts.at(ii)->scriptData()->scriptValueForContext(qmlContextData)));
+    for (int ii = 0; ii < scripts.count(); ++ii) {
+        v = scripts.at(ii)->scriptData()->scriptValueForContext(qmlContextData.data());
+        scriptsArray->put(ii, v);
+    }
 
     return qmlContextData;
 }
 
-QV4::ReturnedValue QQmlScriptData::scriptValueForContext(QQmlContextData *parentQmlContextData)
+QV4::ReturnedValue QQmlScriptData::scriptValueForContext(
+        const QQmlRefPointer<QQmlContextData> &parentQmlContextData)
 {
     if (m_loaded)
         return m_value.value();
 
-    Q_ASSERT(parentQmlContextData && parentQmlContextData->engine);
-    QV4::ExecutionEngine *v4 = parentQmlContextData->engine->handle();
+    Q_ASSERT(parentQmlContextData && parentQmlContextData->engine());
+    QV4::ExecutionEngine *v4 = parentQmlContextData->engine()->handle();
     QV4::Scope scope(v4);
 
     if (!hasEngine()) {
-        addToEngine(parentQmlContextData->engine);
+        addToEngine(parentQmlContextData->engine());
         addref();
     }
 
-    QQmlContextDataRef qmlContextData = qmlContextDataForContext(parentQmlContextData);
     QV4::Scoped<QV4::QmlContext> qmlExecutionContext(scope);
-    if (qmlContextData)
-        qmlExecutionContext =
-                QV4::QmlContext::create(v4->rootContext(), qmlContextData, /* scopeObject: */ nullptr);
+    if (auto qmlContextData = qmlContextDataForContext(parentQmlContextData)) {
+        qmlExecutionContext = QV4::QmlContext::create(v4->rootContext(), std::move(qmlContextData),
+                                                      /* scopeObject: */ nullptr);
+    }
 
     QV4::Scoped<QV4::Module> module(scope, m_precompiledScript->instantiate(v4));
     if (module) {
-        if (qmlContextData) {
+        if (qmlExecutionContext) {
             module->d()->scope->outer.set(v4, qmlExecutionContext->d());
             qmlExecutionContext->d()->qml()->module.set(v4, module->d());
         }
@@ -141,7 +145,7 @@ QV4::ReturnedValue QQmlScriptData::scriptValueForContext(QQmlContextData *parent
     }
 
     QV4::ScopedValue value(scope);
-    if (qmlContextData)
+    if (qmlExecutionContext)
         value = qmlExecutionContext->d()->qml();
     else if (module)
         value = module->d();