Force models and workerscript plugins to link their libraries

Some linkers can determine that we don't use any symbols from the
QtQmlModels and QtQmlWorkerScript libraries in the respective plugins
and avoid to link the libraries into the plugins. That means, when
loading the plugins, the types are not registered. We avoid that by
adding a debug message that accesses a symbol of the library to each
plugin.

Change-Id: I3d946259df96382a3751eaafa12cbdd3d830c139
Fixes: QTBUG-81721
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

1 files changed, 15 insertions, 2 deletions

diff --git a/src/imports/models/plugin.cpp b/src/imports/models/plugin.cpp
index d79b31bba5..4aa9f27766 100644
--- a/src/imports/models/plugin.cpp
+++ b/src/imports/models/plugin.cpp
@@ -37,13 +37,17 @@
 **
 ****************************************************************************/
 
+#include <QtQmlModels/private/qqmlobjectmodel_p.h>
+
 #include <QtQml/qqmlextensionplugin.h>
 #include <QtQml/qqml.h>
 
-#include <private/qqmlmodelsmodule_p.h>
+#include <QtCore/qloggingcategory.h>
 
 QT_BEGIN_NAMESPACE
 
+Q_LOGGING_CATEGORY(qmlModelsPlugin, "qt.qmlModelsPlugin")
+
 /*!
     \qmlmodule QtQml.Models 2.\QtMinorVersion
     \title Qt QML Models QML Types
@@ -86,7 +90,16 @@ class QtQmlModelsPlugin : public QQmlEngineExtensionPlugin
     Q_OBJECT
     Q_PLUGIN_METADATA(IID QQmlEngineExtensionInterface_iid)
 public:
-    QtQmlModelsPlugin(QObject *parent = nullptr) : QQmlEngineExtensionPlugin(parent) { }
+    QtQmlModelsPlugin(QObject *parent = nullptr) : QQmlEngineExtensionPlugin(parent)
+    {
+        if (qmlModelsPlugin().isDebugEnabled()) {
+            // Superficial debug message that causes the dependency between QtQmlWorkerScript
+            // and the workerscript plugin to be retained.
+            // As qCDebug() can be a noop, retrieve the className in a separate step.
+            const QString className = QQmlObjectModel::staticMetaObject.className();
+            qCDebug(qmlModelsPlugin) << "Loading QmlModels plugin:" << className;
+        }
+    }
 };
 //![class decl]