QML list property: Avoid crash if contained object is deleted

Task-number: QTBUG-81123
Change-Id: I3dd1a42e444f817722368cd268c2f987a99fbf1c
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>
(cherry picked from commit e5570eecd3a4fc61020d28699169707a2c1f5dc9)

2 files changed, 56 insertions, 0 deletions

diff --git a/tests/auto/qml/qqmllanguage/data/listContainingDeleted.qml b/tests/auto/qml/qqmllanguage/data/listContainingDeleted.qml
new file mode 100644
index 0000000000..efd273ddc6
--- /dev/null
+++ b/tests/auto/qml/qqmllanguage/data/listContainingDeleted.qml
@@ -0,0 +1,36 @@
+import QtQuick 2.12
+
+Item {
+    width: 1024
+    height: 800
+
+    property Component a: Component {
+        id: a
+        Item {
+            property list<QtObject> myList: [
+                QtObject {
+                    property bool enabled: true
+                }
+            ]
+        }
+    }
+    Component {
+        id: b
+        Item {
+            property list<QtObject> myList
+
+            function test() {
+                for (var i = 0; i < myList.length; ++i)
+                    console.log(i, "==", myList[i].enabled)
+            }
+        }
+    }
+    property Item instance
+    function doAssign(o) {
+        instance = b.createObject(null, {myList: o.myList})
+    }
+    function use() {
+        instance.test()
+    }
+
+}
diff --git a/tests/auto/qml/qqmllanguage/tst_qqmllanguage.cpp b/tests/auto/qml/qqmllanguage/tst_qqmllanguage.cpp
index 87468c329c..d7ef9999d0 100644
--- a/tests/auto/qml/qqmllanguage/tst_qqmllanguage.cpp
+++ b/tests/auto/qml/qqmllanguage/tst_qqmllanguage.cpp
@@ -303,6 +303,8 @@ private slots:
 
     void typeWrapperToVariant();
 
+    void listContainingDeletedObject();
+
 private:
     QQmlEngine engine;
     QStringList defaultImportPathList;
@@ -5100,6 +5102,24 @@ void tst_qqmllanguage::typeWrapperToVariant()
     QVERIFY(target);
 }
 
+void tst_qqmllanguage::listContainingDeletedObject()
+{
+    QQmlEngine engine;
+    auto url = testFileUrl("listContainingDeleted.qml");
+    const QString message = url.toString() + ":24: TypeError: Cannot read property 'enabled' of null";
+    QTest::ignoreMessage(QtMsgType::QtWarningMsg, message.toUtf8().data());
+    QQmlComponent comp(&engine, url);
+    QScopedPointer<QObject> root(comp.create());
+    QVERIFY(root);
+
+    auto cmp = root->property("a").value<QQmlComponent*>();
+    auto o = cmp->create();
+
+    QMetaObject::invokeMethod(root.get(), "doAssign", Q_ARG(QVariant, QVariant::fromValue(o)));
+    delete o;
+    QMetaObject::invokeMethod(root.get(), "use");
+
+}
 QTEST_MAIN(tst_qqmllanguage)
 
 #include "tst_qqmllanguage.moc"