QML: Fix registering and unregistering of context objects

When we add a context object we need to include it into the list of
contextObjects of its outer context, so that the outerContext member can
be reset when the outer context disappears. On the flip side, we also
need to remove it from this list when the object gets removed. We don't
need to reset the inner context of an object when the outer context
disappears, though.

Fixes: QTBUG-72241
Change-Id: Ifd34650d852642a364df23b697d32e3961d0479b
Reviewed-by: Mitch Curtis <mitch.curtis@qt.io>
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

4 files changed, 22 insertions, 13 deletions

diff --git a/src/qml/qml/qqmlcontext.cpp b/src/qml/qml/qqmlcontext.cpp
index cbf5a6e259..eca00ffb51 100644
--- a/src/qml/qml/qqmlcontext.cpp
+++ b/src/qml/qml/qqmlcontext.cpp
@@ -640,7 +640,6 @@ void QQmlContextData::destroy()
         QQmlData *co = contextObjects;
         contextObjects = contextObjects->nextContextObject;
 
-        co->context = nullptr;
         co->outerContext = nullptr;
         co->nextContextObject = nullptr;
         co->prevContextObject = nullptr;
@@ -783,13 +782,17 @@ void QQmlContextData::refreshExpressions()
     }
 }
 
-void QQmlContextData::addObject(QObject *o)
+void QQmlContextData::addObject(QQmlData *data)
 {
-    QQmlData *data = QQmlData::get(o, true);
-
-    Q_ASSERT(data->context == nullptr);
+    if (data->outerContext) {
+        if (data->nextContextObject)
+            data->nextContextObject->prevContextObject = data->prevContextObject;
+        if (data->prevContextObject)
+            *data->prevContextObject = data->nextContextObject;
+        else if (data->outerContext->contextObjects == data)
+            data->outerContext->contextObjects = data->nextContextObject;
+    }
 
-    data->context = this;
     data->outerContext = this;
 
     data->nextContextObject = contextObjects;
diff --git a/src/qml/qml/qqmlcontext_p.h b/src/qml/qml/qqmlcontext_p.h
index 290b7fc7ee..7e3cef8e1d 100644
--- a/src/qml/qml/qqmlcontext_p.h
+++ b/src/qml/qml/qqmlcontext_p.h
@@ -129,7 +129,7 @@ public:
     void setParent(QQmlContextData *, bool stronglyReferencedByParent = false);
     void refreshExpressions();
 
-    void addObject(QObject *);
+    void addObject(QQmlData *data);
 
     QUrl resolvedUrl(const QUrl &);
 
diff --git a/src/qml/qml/qqmlengine.cpp b/src/qml/qml/qqmlengine.cpp
index c400e9239b..6db43a50eb 100644
--- a/src/qml/qml/qqmlengine.cpp
+++ b/src/qml/qml/qqmlengine.cpp
@@ -1518,7 +1518,9 @@ void QQmlEngine::setContextForObject(QObject *object, QQmlContext *context)
     }
 
     QQmlContextData *contextData = QQmlContextData::get(context);
-    contextData->addObject(object);
+    Q_ASSERT(data->context == nullptr);
+    data->context = contextData;
+    contextData->addObject(data);
 }
 
 /*!
@@ -1882,6 +1884,8 @@ void QQmlData::destroyed(QObject *object)
         nextContextObject->prevContextObject = prevContextObject;
     if (prevContextObject)
         *prevContextObject = nextContextObject;
+    else if (outerContext && outerContext->contextObjects == this)
+        outerContext->contextObjects = nextContextObject;
 
     QQmlAbstractBinding *binding = bindings;
     while (binding) {
diff --git a/src/qml/qml/qqmlobjectcreator.cpp b/src/qml/qml/qqmlobjectcreator.cpp
index c181d791f5..68e2c2c928 100644
--- a/src/qml/qml/qqmlobjectcreator.cpp
+++ b/src/qml/qml/qqmlobjectcreator.cpp
@@ -1230,13 +1230,15 @@ QObject *QQmlObjectCreator::createInstance(int index, QObject *parent, bool isCo
             QQmlContextData *c = ddata->context;
             while (c->linkedContext) c = c->linkedContext;
             c->linkedContext = context;
-        } else
-            context->addObject(instance);
+        } else {
+            ddata->context = context;
+        }
         ddata->ownContext = ddata->context;
-    } else if (!ddata->context)
-        context->addObject(instance);
+    } else if (!ddata->context) {
+        ddata->context = context;
+    }
 
-    ddata->outerContext = context;
+    context->addObject(ddata);
 
     if (parserStatus) {
         parserStatus->classBegin();