Re-apply the cast part of commit 392c7b99348e2a96ef11adb5712095fbd13fb780

We reverted this in 6f59c91c51edd7207635c3fa2f0b2b1179e7aa6e to avoid further
breakage in a patch release. Now let's do the right thing in the next minor
release and replace the qobject_cast on the instance with the IID check that
won't require instantiating the plugin in the qml loader thread.

[ChangeLog][QtQml][Important Behavior Changes] When the engine looks for QML
modules / extension plugins in statically linked applications, the plugins are
not instantiated in the qml loader thread anymore. For this to work however
it is necessary for plugins to use Q_PLUGIN_METADATA(IID QQmlExtensionInterface_iid)
in their class declaration instead of hardcoding the interface id as a string
literal.

Task-number: QTBUG-52012
Change-Id: I45fe8b9fec23b3d0408b7ee79ce297c7d47ce36d
Reviewed-by: Sebastian Lösch <Sebastian.Loesch@governikus.com>
Reviewed-by: J-P Nurmi <jpnurmi@qt.io>

1 files changed, 1 insertions, 1 deletions

diff --git a/src/qml/qml/qqmlimport.cpp b/src/qml/qml/qqmlimport.cpp
index 8a7fa369e6..5ed2ad6bf1 100644
--- a/src/qml/qml/qqmlimport.cpp
+++ b/src/qml/qml/qqmlimport.cpp
@@ -893,7 +893,7 @@ bool QQmlImportsPrivate::populatePluginPairVector(QVector<StaticPluginPair> &res
         // To avoid traversing all static plugins for all imports, we cut down
         // the list the first time called to only contain QML plugins:
         foreach (const QStaticPlugin &plugin, QPluginLoader::staticPlugins()) {
-            if (qobject_cast<QQmlExtensionPlugin *>(plugin.instance()))
+            if (plugin.metaData().value(QStringLiteral("IID")).toString() == QLatin1String(QQmlExtensionInterface_iid))
                 plugins.append(plugin);
         }
     }