Deprecate QQmlExtensionPlugin::baseUrl()

The function does not play well with optional plugins as we don't need
to load those from any specific location. You also don't need this
function. There is exactly one place in qtdeclarative where it is used
and there it just provides a poor replacement for qmldir entries.

[ChangeLog][QtQml][Important Behavior Changes] The internal function
QQmlExtensionPlugin::baseUrl() has been deprecated. You don't need it
if you properly specify your module in the qmldir file.

Change-Id: I131c45e069e9c10744a0ad6126604a2600a6d93d
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

src/qml/qml/qqmlextensionplugin.cpp

@@ -75,7 +75,11 @@ QT_BEGIN_NAMESPACE
     \internal
 */
 QQmlExtensionPlugin::QQmlExtensionPlugin(QObject *parent)
+#if QT_DEPRECATED_SINCE(6, 3)
     : QObject(*(new QQmlExtensionPluginPrivate), parent)
+#else
+    : QObject(parent)
+#endif
 {
 }
 
@@ -102,19 +106,31 @@ QQmlExtensionPlugin::~QQmlExtensionPlugin() = default;
  */
 QQmlEngineExtensionPlugin::~QQmlEngineExtensionPlugin() = default;
 
+#if QT_DEPRECATED_SINCE(6, 3)
 /*!
     \since 5.1
     \internal
+    \deprecated [6.3] This is unnecessary and doesn't work for optional plugins
     \brief Returns the URL of the directory from which the extension is loaded.
 
     This is useful when the plugin also needs to load QML files or other
     assets from the same directory.
+
+    \note You should not need this function. Other files that are part of the
+          module's public interface should be specified accordingly in the build
+          system and qmldir file. The build system makes sure that they end up
+          both in the final module directory, and in the resource file system.
+          You can use the copy from the resource file system in the plugin.
+          Non-QML/JS files private to the plugin can be added to the resource
+          file system manually. However, consider moving all such functionality
+          out of the plugin and making the plugin optional.
 */
 QUrl QQmlExtensionPlugin::baseUrl() const
 {
     Q_D(const QQmlExtensionPlugin);
     return d->baseUrl;
 }
+#endif
 
 /*!
   \since 6.0

src/qml/qml/qqmlextensionplugin.h

@@ -61,7 +61,10 @@ public:
     explicit QQmlExtensionPlugin(QObject *parent = nullptr);
     ~QQmlExtensionPlugin() override;
 
+#if QT_DEPRECATED_SINCE(6, 3)
+    QT_DEPRECATED_VERSION_X_6_3("Provide a qmldir file to remove the need for calling baseUrl")
     QUrl baseUrl() const;
+#endif
 
     void registerTypes(const char *uri) override = 0;
     virtual void unregisterTypes();

src/qml/qml/qqmlextensionplugin_p.h

@@ -56,6 +56,7 @@
 
 QT_BEGIN_NAMESPACE
 
+#if QT_DEPRECATED_SINCE(6, 3)
 class QQmlExtensionPluginPrivate : public QObjectPrivate
 {
     Q_DECLARE_PUBLIC(QQmlExtensionPlugin)
@@ -66,6 +67,7 @@ public:
     QUrl baseUrl;
 
 };
+#endif
 
 QT_END_NAMESPACE
 

src/qml/qml/qqmlmetatype.cpp

@@ -845,11 +845,13 @@ QQmlMetaType::RegistrationResult QQmlMetaType::registerPluginTypes(
                 return RegistrationResult::Failure;
             }
 
+#if QT_DEPRECATED_SINCE(6, 3)
             if (auto *plugin = qobject_cast<QQmlExtensionPlugin *>(instance)) {
                 // basepath should point to the directory of the module, not the plugin file itself:
                 QQmlExtensionPluginPrivate::get(plugin)->baseUrl
                         = QQmlImports::urlFromLocalFileOrQrcOrUrl(basePath);
             }
+#endif
 
             const QByteArray bytes = uri.toUtf8();
             const char *moduleId = bytes.constData();

tests/auto/qml/qqmlmoduleplugin/moduleWithQmlSingleton/plugin.cpp

@@ -42,8 +42,7 @@ public:
     void registerTypes(const char *uri) override
     {
         Q_ASSERT(QLatin1String(uri) == "org.qtproject.ModuleWithQmlSingleton");
-        qmlRegisterSingletonType(baseUrl().resolved(QUrl("ModuleWithQmlSingleton/MySingleton.qml")), uri, 1, 0, "MySingleton");
+        qmlRegisterModule(uri, 1, 0);
-        qmlRegisterSingletonType(baseUrl().resolved(QUrl("ModuleWithQmlSingleton/MySingleton2.qml")), uri, 1, 0, "MySingleton2");
     }
 };
 

tests/auto/qml/qqmlmoduleplugin/moduleWithQmlSingleton/qmldir

@@ -1,2 +1,4 @@
 module org.qtproject.ModuleWithQmlSingleton
 plugin moduleWithQmlSingleton
+singleton MySingleton 1.0 MySingleton.qml
+singleton MySingleton2 1.0 MySingleton2.qml

tests/auto/qml/qqmlmoduleplugin/tst_qqmlmoduleplugin.cpp

@@ -809,6 +809,7 @@ void tst_qqmlmoduleplugin::multiSingleton()
     qmlRegisterSingletonInstance("Test", 1, 0, "Tracker", &obj);
     engine.addImportPath(m_importsDirectory);
     QQmlComponent component(&engine, testFileUrl("multiSingleton.qml"));
+    QVERIFY2(component.isReady(), qPrintable(component.errorString()));
     QObject *object = component.create();
     QVERIFY(object != nullptr);
     QCOMPARE(obj.objectName(), QLatin1String("first"));